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1

Glass fibers and vapor phase components of cigarette smoke as cofactors in experimental respiratory tract carcinogenesis  

SciTech Connect

Syrian golden hamsters were given intratracheal instillations of glass fibers with or without BP suspended in saline, once a fortnight for 52 weeks; the experiment was terminated at week 85. No tumors of the respiratory tract were observed in hamsters treated with glass fibers alone. There was no indication that glass fibers enhanced the development of respiratory tract tumors induced by BP. In another study Syrian golden hamsters were exposed to fresh air or to a mixture of 4 major vapor phase components of cigarette smoke, viz. isoprene (800----700 ppm), methyl chloride (1000----900 ppm), methyl nitrite (200----190 ppm) and acetaldehyde (1400----1200 ppm) for a period of at most 23 months. Some of the animals were also given repeated intratracheal instillations of BP or norharman in saline. Laryngeal tumors were found in 7/31 male and 6/32 female hamsters exposed only to the vapor mixture, whereas no laryngeal tumors occurred in controls. The tumor response of the larynx most probably has to be ascribed entirely to the action of acetaldehyde. Simultaneous treatment with norharman or BP did not affect the tumor response of the larynx. Acetaldehyde may occur in the vapor phase of cigarette smoke at levels up to 2000 ppm. Chronic inhalation exposure of rats to acetaldehyde at levels of 0 (controls), 750, 1500 or 3000----1000 ppm resulted in a high incidence of nasal carcinomas, both squamous cell carcinomas of the respiratory epithelium and adenocarcinomas of the olfactory epithelium. It was discussed that acetaldehyde may significantly contribute to the induction of bronchogenic cancer by cigarette smoke in man.

Feron, V.J.; Kuper, C.F.; Spit, B.J.; Reuzel, P.G.; Woutersen, R.A.

1985-01-01

2

E-Cigarette Vapor Contains Potentially Harmful Particles  

MedlinePLUS

... e-cigarettes, and are designed to vaporize liquid nicotine quickly to give users a bigger nicotine kick. These studies provide even more impetus for ... the liquid carrier into which all of the nicotine, flavorings and preservatives easily dissolve, Thornburg said. Those ...

3

Vapor phase pyrolysis  

NASA Technical Reports Server (NTRS)

The vapor phase pyrolysis process is designed exclusively for the lunar production of oxygen. In this concept, granulated raw material (soil) that consists almost entirely of metal oxides is vaporized and the vapor is raised to a temperature where it dissociates into suboxides and free oxygen. Rapid cooling of the dissociated vapor to a discrete temperature causes condensation of the suboxides, while the oxygen remains essentially intact and can be collected downstream. The gas flow path and flow rate are maintained at an optimum level by control of the pressure differential between the vaporization region and the oxygen collection system with the aid of the environmental vacuum.

Steurer, Wolfgang

1992-01-01

4

Chemical hazards present in liquids and vapors of electronic cigarettes.  

PubMed

Electronic (e-)cigarettes have emerged in recent years as putative alternative to conventional tobacco cigarettes. These products do not contain typical carcinogens that are present in tobacco smoke, due to the lack of combustion. However, besides nicotine, hazards can also arise from other constituents of liquids, such as solvents, flavors, additives and contaminants. In this study, we have analyzed 28 liquids of seven manufacturers purchased in Germany. We confirm the presence of a wide range of flavors to enhance palatability. Although glycerol and propylene glycol were detected in all samples, these solvents had been replaced by ethylene glycol as dominant compound in five products. Ethylene glycol is associated with markedly enhanced toxicological hazards when compared to conventionally used glycerol and propylene glycol. Additional additives, such as coumarin and acetamide, that raise concerns for human health were detected in certain samples. Ten out of 28 products had been declared "free-of-nicotine" by the manufacturer. Among these ten, seven liquids were identified containing nicotine in the range of 0.1-15 µg/ml. This suggests that "carry over" of ingredients may occur during the production of cartridges. We have further analyzed the formation of carbonylic compounds in one widely distributed nicotine-free brand. Significant amounts of formaldehyde, acetaldehyde and propionaldehyde were only found at 150 °C by headspace GC-MS analysis. In addition, an enhanced formation of aldehydes was found in defined puff fractions, using an adopted machine smoking protocol. However, this effect was delayed and only observed during the last third of the smoking procedure. In the emissions of these fractions, which represent up to 40 % of total vapor volume, similar levels of formaldehyde were detected when compared to conventional tobacco cigarettes. By contrast, carbonylic compounds were hardly detectable in earlier collected fractions. Our data demonstrate the necessity of standardized machine smoking protocols to reliably address putative risks of e-cigarettes for consumers. PMID:24958024

Hutzler, Christoph; Paschke, Meike; Kruschinski, Svetlana; Henkler, Frank; Hahn, Jürgen; Luch, Andreas

2014-07-01

5

Evaluation of the Genotoxic and Cytotoxic Potential of Mainstream Whole Smoke and Smoke Condensate from a Cigarette Containing a Novel Carbon Filter  

Microsoft Academic Search

A novel carbon filter has been developed which primarily reduces the amount of certain vapor phase constituents of tobacco smoke with greater efficiency than the charcoal filters of cigarettes currently in the market.In vitroindicators of genotoxic and cytotoxic potential were used to compare the cigarette smoke condensate (particulate phase) or whole cigarette smoke (vapor phase and particulate phase) from cigarettes

D. W. Bombick; B. Reed Bombick; P. H. Ayres; K. Putnam; J. Avalos; M. F. Borgerding; D. J. Doolittle

1997-01-01

6

Vapor phase heat transport systems  

SciTech Connect

Vapor phase heat-transport systems are being tested in two of the passive test cells at Los Alamos. The systems consist of an active fin-and-tube solar collector and a condenser inside a water storage tank. The refrigerant, R-11, can be returned to the collector by a pump or by a self-pumping scheme. In one of the test cells the liquid was self-pumped to the roof-mounted collector 17 ft above the condenser. A mechanical valve was designed and tested that showed that the system could operate in a completely passive mode. Performance comparisons have been made with a passive water wall test cell.

Hedstrom, J.C.

1984-01-01

7

Peptides and Proteins in the Vapor Phase  

NASA Astrophysics Data System (ADS)

This article provides a review of recent studies of the properties of unsolvated (and partially solvated) peptides and proteins. The methods used to produce vapor-phase peptide and protein ions are described along with some of the techniques used to study them, such as H/D exchange, blackbody infrared radiative dissociation, and ion mobility measurements. Studies of unsolvated peptides and proteins provide information about their intrinsic intramolecular interactions. The topics covered include the role of zwitterions and salt bridges in the vapor phase, Coulomb interactions in multiply charged ions, the unfolding and refolding of vapor-phase proteins, and the stability of unsolvated helices and sheets. Finally, dehydration and rehydration studies of proteins in the vapor phase are described. These can provide exquisitely detailed information about hydration interactions, such as the enthalpy and entropy changes associated with adsorbing individual water molecules.

Jarrold, Martin F.

2000-10-01

8

A Protocol for Detecting and Scavenging Gas-phase Free Radicals in Mainstream Cigarette Smoke  

PubMed Central

Cigarette smoking is associated with human cancers. It has been reported that most of the lung cancer deaths are caused by cigarette smoking 5,6,7,12. Although tobacco tars and related products in the particle phase of cigarette smoke are major causes of carcinogenic and mutagenic related diseases, cigarette smoke contains significant amounts of free radicals that are also considered as an important group of carcinogens9,10. Free radicals attack cell constituents by damaging protein structure, lipids and DNA sequences and increase the risks of developing various types of cancers. Inhaled radicals produce adducts that contribute to many of the negative health effects of tobacco smoke in the lung3. Studies have been conducted to reduce free radicals in cigarette smoke to decrease risks of the smoking-induced damage. It has been reported that haemoglobin and heme-containing compounds could partially scavenge nitric oxide, reactive oxidants and carcinogenic volatile nitrosocompounds of cigarette smoke4. A 'bio-filter' consisted of haemoglobin and activated carbon was used to scavenge the free radicals and to remove up to 90% of the free radicals from cigarette smoke14. However, due to the cost-ineffectiveness, it has not been successfully commercialized. Another study showed good scavenging efficiency of shikonin, a component of Chinese herbal medicine8. In the present study, we report a protocol for introducing common natural antioxidant extracts into the cigarette filter for scavenging gas phase free radicals in cigarette smoke and measurement of the scavenge effect on gas phase free radicals in mainstream cigarette smoke (MCS) using spin-trapping Electron Spin Resonance (ESR) Spectroscopy1,2,14. We showed high scavenging capacity of lycopene and grape seed extract which could point to their future application in cigarette filters. An important advantage of these prospective scavengers is that they can be obtained in large quantities from byproducts of tomato or wine industry respectively11,13

Yu, Long-Xi; Dzikovski, Boris G.; Freed, Jack H.

2012-01-01

9

A protocol for detecting and scavenging gas-phase free radicals in mainstream cigarette smoke.  

PubMed

Cigarette smoking is associated with human cancers. It has been reported that most of the lung cancer deaths are caused by cigarette smoking (5,6,7,12). Although tobacco tars and related products in the particle phase of cigarette smoke are major causes of carcinogenic and mutagenic related diseases, cigarette smoke contains significant amounts of free radicals that are also considered as an important group of carcinogens(9,10). Free radicals attack cell constituents by damaging protein structure, lipids and DNA sequences and increase the risks of developing various types of cancers. Inhaled radicals produce adducts that contribute to many of the negative health effects of tobacco smoke in the lung(3). Studies have been conducted to reduce free radicals in cigarette smoke to decrease risks of the smoking-induced damage. It has been reported that haemoglobin and heme-containing compounds could partially scavenge nitric oxide, reactive oxidants and carcinogenic volatile nitrosocompounds of cigarette smoke(4). A 'bio-filter' consisted of haemoglobin and activated carbon was used to scavenge the free radicals and to remove up to 90% of the free radicals from cigarette smoke(14). However, due to the cost-ineffectiveness, it has not been successfully commercialized. Another study showed good scavenging efficiency of shikonin, a component of Chinese herbal medicine(8). In the present study, we report a protocol for introducing common natural antioxidant extracts into the cigarette filter for scavenging gas phase free radicals in cigarette smoke and measurement of the scavenge effect on gas phase free radicals in mainstream cigarette smoke (MCS) using spin-trapping Electron Spin Resonance (ESR) Spectroscopy(1,2,14). We showed high scavenging capacity of lycopene and grape seed extract which could point to their future application in cigarette filters. An important advantage of these prospective scavengers is that they can be obtained in large quantities from byproducts of tomato or wine industry respectively(11,13). PMID:22230844

Yu, Long-Xi; Dzikovski, Boris G; Freed, Jack H

2012-01-01

10

Application of Thioether for Vapor Phase Lubrication  

NASA Technical Reports Server (NTRS)

The objective of these studies was to identify the optimal conditions for vapor phase lubrication using Thioether for both sliding and rolling wear. The important variable include; (1) The component materials including M50 steel, monel and silicon nitride. (2) The vapor concentration and flow rate. (3) The temperature in the range of 600 F to 1500 F. (4) The loads and rolling and/or sliding speeds.

Graham, E. Earl

1997-01-01

11

Artifactual chemiluminescence in the determination of nitrogen monoxide in the vapour phase of mainstream cigarette smoke.  

PubMed

Evidence is presented for the artifactual chemiluminescence from olefins in the determination of nitrogen monoxide in the vapour phase of mainstream cigarette smoke. The interference may be quantified by measuring the residual chemiluminescence remaining in the vapour phase of mainstream cigarette smoke after 24 h. For the nitrogen monoxide analyser used, corrections to the yield of most cigarette brands retailed in the UK were found to be about 1.5 micrograms of nitrogen monoxide per puff, each machine puff being defined by international standards. PMID:2712309

Houlgate, P R; Evans, W H

1989-01-01

12

COMPARATIVE YIELDS OF MUTAGENS FROM CIGARETTE SMOKERS' URINE OBTAINED BY USING SOLID-PHASE EXTRACTION TECHNIQUES  

EPA Science Inventory

Urine from cigarette smokers was prepared for mutagenicity testing by extracting mutagens with solid phase extraction columns. ommercially available prepacked bonded silicas (cotadecyl, cyclohexyl, cyanopropyl) were compared for their efficiency and specificity in concentration o...

13

Vapor-phase soldering techniques. Final report  

SciTech Connect

The general process instructions for vapor phase soldering are given. These instructions discuss reflow soldering, rework of discrepant material, and maintenance and calibration of the equipment involved. The requirements for soldering discrete components to thick film conductors is also discussed, along with quality assurance and packaging requirements for those components.

Uthe, E.M.

1983-07-01

14

Vapor-liquid phase separator permeability results  

NASA Technical Reports Server (NTRS)

Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

Yuan, S. W. K.; Frederking, T. H. K.

1981-01-01

15

Vapor-liquid phase separator studies  

NASA Technical Reports Server (NTRS)

Porous plugs serve as both entropy rejection devices and phase separation components separating the vapor phase on the downstream side from liquid Helium 2 upstream. The liquid upstream is the cryo-reservoir fluid needed for equipment cooling by means of Helium 2, i.e Helium-4 below its lambda temperature in near-saturated states. The topics outlined are characteristic lengths, transport equations and plug results.

Yuan, S. W. K.; Lee, J. M.; Kim, Y. I.; Hepler, W. A.; Frederking, T. H. K.

1983-01-01

16

Carbonyl compounds in gas and particle phases of mainstream cigarette smoke.  

PubMed

Carbonyl compounds (carbonyls) are important constituents of cigarette smoke and some are toxic and may be carcinogenic or mutagenic to humans. In this study carbonyl emissions in the gas and particle phases of mainstream cigarette smoke were assessed by GC-MS with pentafluorophenyl hydrazine (PFPH) derivatization. Seven brands of cigarettes and one brand of cigar common in the UK market and having differing nicotine, tar and carbon monoxide yields were investigated. Sixteen carbonyl components were identified in gaseous emissions and twenty in the particle phase. In the gaseous emissions, acetaldehyde presented as the predominant species, followed by formaldehyde, 2-propenal, and pentanal. In the particulate emissions, 1-hydroxy-2-propanone was the most abundant followed by formaldehyde, benzaldehyde, and 2,5-dimethylbenzaldehyde. Significant differences were found in carbonyl emissions among the brands of cigarettes. The gaseous carbonyl emissions varied in the range of 216-405 ?g cigarette(-1) (?g cig(-1)) and the particulate carbonyl emissions varied in the range of 23-127 ?g cig(-1). Positive correlations were found between the total emission of carbonyls, tar yield and carbon monoxide yield. Similar gas/particle (G/P) partitioning ratios of carbonyls were found among all cigarettes, which implies that G/P partitions of carbonyls in smoke mainly depend on the physical properties of the carbonyls. The gaseous carbonyl emissions were enhanced by 40% to 130% when some of the water, accounting for 8-12% of cigarettes in mass, was removed from the tobacco. Non-filtered cigarettes showed significantly higher carbonyl emissions compared to their filtered equivalents. Carbonyl particulate accounted for 11-19% by mass of total particulate matter from tobacco smoke. The cigar generated 806 ?g cig(-1) gaseous and 141 ?g cig(-1) particulate carbonyls, which is 2-4 times greater than the cigarettes. PMID:21925713

Pang, Xiaobing; Lewis, Alastair C

2011-11-01

17

Liquid-phase compositions from vapor-phase analyses  

SciTech Connect

Arsenic normally is not considered to be a contaminant. However, because arsenic was found in many cylinders of UF{sub 6}, including in corrosion products, a study was performed of the distribution of the two arsenic fluorides, AsF{sub 3} and AsF{sub 5}, between liquid and vapor phases. The results of the study pertain to condensation or vaporization of liquid UF{sub 6}. This study includes use of various experimental data plus many extrapolations necessitated by the meagerness of the experimental data. The results of this study provide additional support for the vapor-liquid equilibrium model of J.M. Prausnitz and his coworkers as a means of describing the distribution of various impurities between vapor and liquid phases of UF{sub 6}. Thus, it is concluded that AsF{sub 3} will tend to concentrate in the liquid phase but that the concentration of AsF{sub 5} in the vapor phase will exceed its liquid-phase concentration by a factor of about 7.5, which is in agreement with experimental data. Because the weight of the liquid phase in a condensation operation may be in the range of thousands of times that of the vapor phase, most of any AsF{sub 5} will be in the liquid phase in spite of this separation factor of 7.5. It may also be concluded that any arsenic fluorides fed into a uranium isotope separation plant will either travel with other low-molecular-weight gases or react with materials present in the plant. 25 refs., 3 figs., 6 tabs.

Davis, W. Jr. (Oak Ridge Gaseous Diffusion Plant, TN (USA)); Cochran, H.D. (Oak Ridge National Lab., TN (USA))

1990-02-01

18

Vapor phase SERS sensor for explosives detection  

Microsoft Academic Search

In the present work, we employ “nanometal-on-semiconductor” SERS substrates to detect various explosives including TNT, PETN, RDX, and TNB in vapor phase at concentrations on the order of few ppb. The SERS substrates were prepared by a novel process, where a monolayer of surfactant-free Ag nanoparticles was reduced on a Si thin film. Our work also targets a clear understanding

Sumedha Tamane; C. Ozge Topal; A. Kaan Kalkan

2011-01-01

19

Gas Phase Oxidants of Cigarette Smoke Increase Nitric Oxide Synthase and Xanthine Oxidase Activities of Rabbit Brain Synaptosomes  

Microsoft Academic Search

In the present study we demonstrated that NO synthase and xanthine oxidase of synaptosomes isolated from rabbit brain cortex can be activated by the gas phase of cigarette smoke to produce nitric oxide and superoxide which react together to form peroxynitrite. Expose of synaptosomes, up to 3 hours, in the gas phase of cigarette smoke, a gradual increase in both

George Deliconstantinos; Vassiliki Villiotou

2000-01-01

20

Liquid-phase compositions from vapor-phase analyses  

SciTech Connect

In the safe handling and processing of uranium hexafluoride (UF{sub 6}), it is often desirable to calculate vapor composition and pressure from known liquid composition and temperature. Furthermore, the ability to use analyses of equilibrium vapor-phase samples to calculate liquid-phase compositions would be economically advantageous to the International Atomic Energy Agency (IAEA) in its international safeguards program and to uranium enrichment operators. The latter technique is projected to save the IAEA on the order of $1500 or more per sample. Either type of calculation could be performed with a multicomponent vapor-liquid equilibrium (VLE) model if this model were shown to apply to UF{sub 6} and its common impurities. This report is concerned with the distribution of four potential impurities in UF{sub 6} between liquid and vapor phases. The impurities are carbon dioxide, sulfur hexafluoride, chloryl fluoride, and Freon-114 (CClF{sub 2}CClF{sub 2}). There are no binary equilibrium data on the first three of these impurities; hence, the VLE calculations are based entirely on the thermodynamic properties of the pure components. There are two sets of binary equilibrium data for the system Freon-114-UF{sub 6} that are analyzed in terms of the model of Prausnitz et al. Calculations based on these data are compared with those based solely on the thermodynamic properties of pure Freon-114 and pure UF{sub 6}. 23 refs., 3 figs., 5 tabs.

Davis, W. Jr.; Cochran, H.D.; Leitnaker, J.M.

1989-09-01

21

[Electronic cigarette].  

PubMed

Electronic cigarette (e-cigarettes) belongs to the "ENDS (Electronic Nicotine Delivery Systems), ie systems that deliver nicotine electronically. Extract of tobacco does not burn, just warm. Vapors may or may not contain nicotine. E-cigarettes are also available with different flavors. They don't produce a classic smoke. There is a large variability of these products. It seems that the initial negative position has to be reconsidered. Although there has been demonstrated trace amounts of several toxic substances in the vapor, the risk compared to traditional smoking is minimal. Moreover, lately it was shown that they can really contribute to smoking quitting. The legislative framework varies considerably, from the prohibition on sales to the recommended assistance in quitting. In the CR they are included according to the Act 379/2005 in 2009 among the tobacco products. PMID:22679688

Králíková, Eva; Jezek, Martin

2012-01-01

22

Mechanistic study of organometallic vapor phase epitaxy  

SciTech Connect

Only AsH{sub 3} and PH{sub 3} have been used as the group V source molecules for organometallic vapor phase epitaxy (OMVPE) of III/V semiconductors until recently, since they have been the only precursors yielding device quality materials. This paper reviews recent work on the pyrolysis of individual organometallic molecules, with emphasis on the group V sources, including: (1) the methylarsines, di- and tri-methylarsine, (2) the ethylarsines, mono-, di-, and tri-ethylarsine, and (3) the singly substituted tertiarybutyl arsine and phosphine molecules. The pyrolysis and growth reactions occurring when both group III and group V precursors are present simultaneously, i.e., the reactions occuring during OMVPE growth of several III/V semiconductors, are also briefly reviewed.

Stringfellow, G.B.

1990-12-31

23

Mechanistic study of organometallic vapor phase epitaxy  

SciTech Connect

Only AsH{sub 3} and PH{sub 3} have been used as the group V source molecules for organometallic vapor phase epitaxy (OMVPE) of III/V semiconductors until recently, since they have been the only precursors yielding device quality materials. This paper reviews recent work on the pyrolysis of individual organometallic molecules, with emphasis on the group V sources, including: (1) the methylarsines, di- and tri-methylarsine, (2) the ethylarsines, mono-, di-, and tri-ethylarsine, and (3) the singly substituted tertiarybutyl arsine and phosphine molecules. The pyrolysis and growth reactions occurring when both group III and group V precursors are present simultaneously, i.e., the reactions occuring during OMVPE growth of several III/V semiconductors, are also briefly reviewed.

Stringfellow, G.B.

1990-01-01

24

Porous polymers by controlling phase separation during vapor deposition polymerization.  

PubMed

A template-free method is described to fabricate continuous-phase, porous polymer films by simultaneous phase separation during vapor deposition polymerization. The technique involves concurrent polymerization, crosslinking, and phase separation of condensed species and reaction products. Deposited films form open-cell, macroporous structures consisting of crosslinked and glassy poly(glycidyl methacrylate). By limiting phase separation during vapor phase deposition, spatially dependent morphologies, such as layered morphologies, can be grown. Results show that combining vapor deposition polymerization with phase separation establishes morphological control, which may be applied to applications including cellular scaffolds, thin cushions and vibration dampers, and membranes for separations. PMID:24123386

Tao, Ran; Anthamatten, Mitchell

2013-11-01

25

Assessment of radionuclide vapor-phase transport in unsaturated tuff  

Microsoft Academic Search

This report describes bounding calculations performed to investigate the possibility of radionuclide migration in a vapor phase associated with the emplacement of high-level waste canister in unsaturated tuff formations. Two potential radionuclide transport mechanisms in the vapor phase were examined: aerosol migration and convection\\/diffusion of volatile species. The former may have significant impact on the release of radionuclides to the

D. M. Smith; C. D. Updegraff; E. J. Bonano; J. D. Randall

1986-01-01

26

The liquid to vapor phase transition in excited nuclei  

SciTech Connect

For many years it has been speculated that excited nuclei would undergo a liquid to vapor phase transition. For even longer, it has been known that clusterization in a vapor carries direct information on the liquid-vapor equilibrium according to Fisher's droplet model. Now the thermal component of the 8 GeV/c pion + 197 Au multifragmentation data of the ISiS Collaboration is shown to follow the scaling predicted by Fisher's model, thus providing the strongest evidence yet of the liquid to vapor phase transition.

Elliott, J.B.; Moretto, L.G.; Phair, L.; Wozniak, G.J.; Beaulieu, L.; Breuer, H.; Korteling, R.G.; Kwiatkowski, K.; Lefort, T.; Pienkowski, L.; Ruangma, A.; Viola, V.E.; Yennello, S.J.

2001-05-08

27

New Vapor/Mist Phase Lubricant Formulated  

NASA Technical Reports Server (NTRS)

To meet the increased thermal stresses of future advanced aircraft engines, new lubricants will have to be developed to replace the currently used ester-based liquid lubricants. If a suitable conventional replacement cannot be found, a different lubrication method will have to be used. The conventional method circulates bulk lubricant (stored in a sump) through a lubricating system containing cooling and filtering elements. Solid lubricants have been studied as a replacement for bulk liquid lubricants, and have been found to provide reasonable lubrication for lightly loaded systems. Solid lubricants, however, have proved inadequate for highly loaded, high-speed applications. Vapor/mist phase lubrication (VMPL), on the other hand, may be a viable alternative. VMPL has been used successfully to lubricate high-temperature bearings or gears. It can be used as an emergency backup system or as the primary source of lubrication. With VMPL, minimal weight is added to the system and minimal debris is formed. It works over a wide temperature range.

Morales, Wilfredo; Handschuh, Robert F.

1999-01-01

28

External fuel vaporization study, phase 1  

NASA Technical Reports Server (NTRS)

A conceptual design study was conducted to devise and evaluate techniques for the external vaporization of fuel for use in an aircraft gas turbine with characteristics similar to the Energy Efficient Engine (E(3)). Three vaporizer concepts were selected and they were analyzed from the standpoint of fuel thermal stability, integration of the vaporizer system into the aircraft engine, engine and vaporizer dynamic response, startup and altitude restart, engine performance, control requirements, safety, and maintenance. One of the concepts was found to improve the performance of the baseline E(3) engine without seriously compromising engine startup and power change response. Increased maintenance is required because of the need for frequent pyrolytic cleaning of the surfaces in contact with hot fuel.

Szetela, E. J.; Chiappetta, L.

1980-01-01

29

Development of Vapor-Phase Catalytic Ammonia Removal System  

NASA Technical Reports Server (NTRS)

A report describes recent accomplishments of a continuing effort to develop the vapor-phase catalytic ammonia removal (VPCAR) process for recycling wastewater for consumption by humans aboard a spacecraft in transit to Mars.

Flynn, Michael; Fisher, John; Kiss, Mark; Borchers, Bruce; Tleimat, Badawi; Tleimat, Maher; Quinn, Gregory; Fort, James; Nalette, Tim; Baker, Gale; Genovese, Joseph

2007-01-01

30

BIOREMEDIATION OF MIXED VAPOR PHASE CONTAMINANTS FROM SOILS AND GROUNDWATER  

EPA Science Inventory

Soil vapor phase contaminants commonly include combinations of chlorinated ethenes and petroleum hydrocarbons. Many chlorinated ethenes and petroleum hydrocarbons are readily degradable by a range of aerobic soil microorganisms, making the use of biological systems for degrading ...

31

Vapor core turbulence in annular two-phase flow  

SciTech Connect

This paper reports a new technique to measure vapor turbulence in two-phase flows using hot-film anemometry. Continuous vapor turbulence measurements along with local void fraction, droplet frequency, droplet velocity and droplet diameter were measured in a thin, vertical duct. By first eliminating the portion of the output voltage signal resulting from the interaction of dispersed liquid droplets with the HFA sensor, the discrete voltage samples associated with the vapor phase were separately analyzed. The data revealed that, over the range of liquid droplet sizes and concentrations encountered, the presence of the droplet field acts to enhance vapor turbulence. In addition, there is evidence that vapor turbulence is significantly influenced by the wall-bounded liquid film. The present results are qualitatively consistent with the limited data available in the open literature.

Trabold, T.A.; Kumar, R. [Lockheed Martin Corp., Schenectady, NY (United States)

1998-06-01

32

Gas phase reaction of sulfur trioxide with water vapor  

Microsoft Academic Search

Sulfur trioxide (SO3) has long been known to react with water to produce sulfuric acid (H2S04). It has been commonly assumed that the gas phase reaction in the Earth`s atmosphere between SO3 and water vapor to produce sulfuric acid vapor is an important step in the production of sulfuric acid aerosol particles. The kinetics of the gas phase reaction of

C. E. Kolb; M. J. Molina; J. T. Jayne; R. F. Meads; D. R. Worsnop; A. A. Viggiano

1994-01-01

33

Hydride vapor phase epitaxy of aluminum nitride  

NASA Astrophysics Data System (ADS)

AlN is a promising substrate material for AlGaN-based UV optoelectronic devices and high-power, high-frequency electronic devices. Since large-area bulk AlN crystals are not readily available, one approach to prepare AlN substrates is to heteroepitaxially deposit thick (e.g., 10-300+ mum) AlN layers by hydride vapor phase epitaxy. Initial efforts focused on growing AlN layers on sapphire substrates with growth rates up to 75 mum/hr. The resulting layers were colorless, smooth, and specular. Subsurface cracking, attributed to the plastic relief of tensile strain from island coalescence, was observed but did not adversely affect the surface morphology of the AlN layers. The surfaces possessed rms roughnesses as low as 0.316 nm over 5 x 5 mum2 sampling areas, but hexagonal hillock formation was observed for thick films grown at high growth rates. TEM revealed that the threading dislocation (TD) density of the films was 2 x 109 cm-2. The high TD densities for direct growth of AlN films on foreign substrates motivated the development of lateral epitaxial overgrowth approaches for defect reduction. Growth of AlN layers on patterned SiC substrates produced coalesced AlN films possessing TD densities below 8.3 x 106 cm -2 in the laterally grown wing regions, as compared to 1.8 x 109 cm-2 in the seed regions. These films, however, cracked on cooldown due to the difference in thermal expansion coefficients for AlN and SiC. To avoid this cracking, AlN layers were grown on patterned sapphire substrates. Although the films were able to be coalesced and contained few or no cracks, the TDs in these films were not confined to the seed regions. This produced a relatively uniform distribution of TDs over the surfaces of the films, with only a modest reduction in the TD density of 1 x 10 8 cm-2. Selective area growth of AlN was also pursued using Si3N4, SiO2, and Ti masks. Growth selectivity and film coalescence was observed for films grown on each masking material, but none of the masks resulted in films with both smooth surface morphologies and low TD densities.

Kamber, Derrick Shane

34

Vapor phase crystallization in Apollo 14 breccia.  

NASA Technical Reports Server (NTRS)

The vugs contained in many of the highly recrystallized breccias from Apollo 14 are discussed, along with the well-developed crystals of plagioclase, pyroxene, ilmenite, apatite, whitlockite, iron, nickel-iron, and troilite that extend from the vug walls and bridge open spaces. These crystals are interpreted as having formed by deposition from a hot vapor containing oxides, halides, sulfides, alkali metals, iron and possibly other chemical species. The hot vapor was associated with the thermal metamorphism and subsequent cooling of the Fra Mauro formation after it had been deposited as an ejecta blanket by the Imbrian impact.

Mckay, D. S.; Clanton, U. S.; Morrison, D. A.; Ladle, G. H.

1972-01-01

35

Activity Estimates of Various Radionuclides in Saltstone Vapor Phase  

Microsoft Academic Search

Savannah River National Laboratory estimated activities of various radionuclides in vapor phase associated with saltstone. These radionuclides, as well as the estimated activity and concentration of each in the gases phase are listed. Some of the activities are so low they should be considered zero. In particular, activity of the antimony and tin isotopes in the gas phase correspond to

2005-01-01

36

The interaction of the theophylline metastable phase with water vapor  

NASA Astrophysics Data System (ADS)

The conditions of hydration of the stable and metastable theophylline phases were determined. Two-phase metastable phase/monohydrate and stable phase/monohydrate equilibrium pressures were measured at 25, 30, and 35°C. The metastable phase began to react with water vapor at lower relative humidities than the stable phase. Processes that occurred with the metastable and stable theophylline phases over various water pressure ranges were considered. The metastable phase exhibited an unusual behavior at 25°C and relative humidity 47%. At constant water vapor pressure and temperature, theophylline was initially hydrated and then lost water and again became anhydrous. Two consecutive processes occurred in the system, the formation of theophylline monohydrate from the metastable phase and its decomposition to the stable phase. The ratio between the rates of these processes determined the content of the monohydrate at the given time moment.

Matvienko, A. A.; Boldyrev, V. V.; Sidel'Nikov, A. A.; Chizhik, S. A.

2008-07-01

37

Vapor Phase Impregnation of Active Carbons.  

National Technical Information Service (NTIS)

The purpose of the research was to study methods for the vapor deposition of metals and metal salts into the pores of activated carbons, and evaluate properties imparted to the carbons for toxic gas removal by this method of impregnation. A successful met...

D. M. Andrews J. P. Redmond

1969-01-01

38

Vapor Phase Deposition Using Plasma Spray-PVD™  

NASA Astrophysics Data System (ADS)

Plasma spray—physical vapor deposition (PS-PVD) is a low pressure plasma spray technology to deposit coatings out of the vapor phase. PS-PVD is a part of the family of new hybrid processes recently developed by Sulzer Metco AG (Switzerland) on the basis of the well-established low pressure plasma spraying (LPPS) technology. Included in this new process family are plasma spray—chemical vapor deposition (PS-CVD) and plasma spray—thin film (PS-TF) processes. In comparison to conventional vacuum plasma spraying and LPPS, these new processes use a high energy plasma gun operated at a work pressure below 2 mbar. This leads to unconventional plasma jet characteristics which can be used to obtain specific and unique coatings. An important new feature of PS-PVD is the possibility to deposit a coating not only by melting the feed stock material which builds up a layer from liquid splats, but also by vaporizing the injected material. Therefore, the PS-PVD process fills the gap between the conventional PVD technologies and standard thermal spray processes. The possibility to vaporize feedstock material and to produce layers out of the vapor phase results in new and unique coating microstructures. The properties of such coatings are superior to those of thermal spray and EB-PVD coatings. This paper reports on the progress made at Sulzer Metco to develop functional coatings build up from vapor phase of oxide ceramics and metals.

von Niessen, K.; Gindrat, M.; Refke, A.

2010-01-01

39

Vapor-Phase Synthesis of Gallium Phosphide Nanowires  

SciTech Connect

Gallium phosphide (GaP) nanowires were synthesized in a high yield by vapor-phase reaction of gallium vapor and phosphorus vapor at 1150 C in a tube furnace system. The nanowires have diameters in the range of 25-100 nm and lengths of up to tens of micrometers. Twinning growth occurs in GaP nanowires, and as a result most nanowires contain a high density of twinning faults. Novel necklacelike GaP nanostructures that were formed by stringing tens of amorphous Ga-P-O microbeads upon one crystalline GaP nanowires were also found in some synthesis runs. This simple vapor-phase approach may be applied to synthesize other important group III-V compound nanowires.

Gu, Dr Zhanjun [University of Georgia, Athens, GA; Paranthaman, Mariappan Parans [ORNL; Pan, Zhengwei [University of Georgia, Athens, GA

2009-01-01

40

Rapid vapor-phase densification of refractory composites  

Microsoft Academic Search

The status of vapor-phase routes for the rapid densification of high-temperature composite materials, primarily ceramic-matrix composites, is reviewed. Conventional densification of composites such as carbon-carbon and SiC-SiC is accomplished by isothermal, isobaric chemical vapor infiltration (CVI), either alone or in combination with liquid resin impregnation and thermal annealing. These are multi-step processes which take from several hundred to thousands of

I. Golecki

1997-01-01

41

Calibration of an explosives vapor generator based on vapor diffusion from a condensed phase  

SciTech Connect

In the field of explosives detection there is currently a need for a calibrated source of explosives vapor. Such a source could be used to test and calibrate explosives detection systems which identify explosives via the collection of vapor or air borne particulate matter. This paper describes the principles of operation and evaluation of one such explosives vapor generator. This generator is based on the diffusion of vapor from a condensed phase (i.e., solid or liquid) in a source reservoir, and the output has been tied to a National Institute of Standards and Technology (NIST) mass standard. We discuss results of the calibration of this generator using the explosives 2,4,6-trinitrotoluene (TNT) and cyclonite (RDX). The mass output of this generator is stable over hundreds of hours of continuous operation, and is adjustable from the low picograms(pg)/sec range to at least 10 nanograms(ng)/sec. In the case of TNT, the mass output correlates well with predictions based on gas phase diffusion theory. In the case of RDX, the agreement with theory is less good. This may be attributable to a variety of factors, possibly including inaccuracies in the published data on RDX vapor pressure as a function of temperature.

Parmeter, J.E. [Sandia National Labs., Albuquerque, NM (United States); Eiceman, G.A.; Preston, D.A.; Tiano, G.S. [New Mexico State Univ., Las Cruces, NM (United States)

1996-08-01

42

High Temperature Vapor Phase Electrolysis (HOT ELLY).  

National Technical Information Service (NTIS)

The objective of the project HOT ELLY (phase 1) was the demonstration of the practicability of high temperature steam electrolysis on a laboratory scale. Starting from basic material studies the components (using sufficiently cheap raw materials), as well...

W. Donitz H. Hermeking I. Kirzmann A. Koch R. Rottenbacher

1982-01-01

43

Assessment of the Vapor Phase Catalytic Ammonia Removal (VPCAR) Technology at the MSFC ECLS Test Facility.  

National Technical Information Service (NTIS)

The Vapor Phase Catalytic Ammonia. Removal (VPCAR) technology has been previously discussed as a viable option for. the Exploration Water Recovery System. This technology integrates a phase change process with catalytic oxidation in the vapor phase to pro...

D. Long K. Tomes L. Carter M. Flynn

2007-01-01

44

Fog Machines, Vapors, and Phase Diagrams  

ERIC Educational Resources Information Center

A series of demonstrations is described that elucidate the operation of commercial fog machines by using common laboratory equipment and supplies. The formation of fogs, or "mixing clouds", is discussed in terms of the phase diagram for water and other chemical principles. The demonstrations can be adapted for presentation suitable for elementary…

Vitz, Ed

2008-01-01

45

Vapor-Phase Infrared Absorptivity Coefficient of HN1.  

National Technical Information Service (NTIS)

We report the vapor-phase IR absorptivity coefficient of the vesicant chemical agent, HN1. The data are provided at a spectral resolution of 0.25 cm 1 (data spacing of 0.125 cm 1). We describe the methods used to generate the spectra, process the raw data...

A. C. Samuels B. R. Williams J. R. Miles M. S. Hulet

2013-01-01

46

Preliminary assessment of radionuclide vapor phase transport in unsaturated tuff  

Microsoft Academic Search

The possibility of radionuclide migration in the vapor phase for unsaturated tuff has been investigated. Radionuclide movement could be the result of either aerosol migration or convection\\/diffusion of volatile species. A diffusion model for supersaturation of air in tuff groundwater indicates that there is no possibility of aerosol formation under expected repository conditions. An assessment of migration due to convection\\/diffusion

D. M. Smith; C. D. Updegraff; E. J. Bonano

1985-01-01

47

Growth of Semiconductor Single Crystals from Vapor Phase  

NASA Astrophysics Data System (ADS)

Growth of single crystals from the vapor phase is considered to be an important method to obtain stoichiometric crystalline materials from inexpensive and readily available raw materials. Elements or compounds which are relatively volatile can be grown from vapor phase. Most II-VI, I-III-VI2, and III-N compounds are high-melting-point materials which may be grown as single crystals by careful use of vapor phase. The chemical vapor transport (CVT) method has been widely used as an advantageous method to grow single crystals of different compounds at temperatures lower than their melting points. This method is quite useful for the growth of II-VI and I-III-VI2 compounds, which generally have high melting point and large dissociation pressure at the melting point. In addition, they undergo solid-state phase transition during cooling or heating processes, which makes the growth of these compounds by some other methods, such as from the melt, difficult. In addition, the low growth temperature involved reduces defects produced by thermal strain, pollution from the crucible, and the cost of the growth equipment. II-VI compound semiconductors cover a very broad range of electronic and optical properties due to the large range of their energy gaps. These materials in the form of bulk single crystals or thin films are used in light emitters, detectors, linear and nonlinear optical devices, semiconductor electronics, and other devices. The development of growth technology for II-VI compound semiconductors from the vapor phase with the necessary theoretical background is important. I-III-VI2 chalcopyrite compounds are of technological interest since they show promise for application in areas of visible and infrared light-emitting diodes, infrared detectors, optical parametric oscillators, upconverters, far-infrared generation, and solar energy conversion.

Dhanasekaran, Ramasamy

48

Measurements of viscosity of refrigerants in the vapor phase  

SciTech Connect

Measurements of the viscosity of refrigerants R124, R125, R134a, and R152a in the vapor phase are presented. The measurements, performed in a new vibrating-wire instrument, cover a temperature range from 273 to 333 K from about atmospheric pressure up to below the saturation pressure. The uncertainty of the reported values is estimated to be better than {+-}1%. Comparison with measurements of other investigators reveals a lack of reliable data in the vapor region for these compounds.

Assael, M.J.; Polimatidou, S.K. [Aristotle Univ., Thessaloniki (Greece). Faculty of Chemical Engineering

1997-03-01

49

Adiabatic nucleation in the liquid-vapor phase transition  

NASA Astrophysics Data System (ADS)

The fundamental difference between classical (isothermal) nucleation theory (CNT) and adiabatic nucleation theory (ANT) is discussed. CNT uses the concept of isothermal heterophase fluctuations, while ANT depends on common fluctuations of the thermodynamic variables. Applications to the nonequilibrium liquid to vapor transition are shown. However, we cannot yet calculate nucleation frequencies. At present, we can only indicate at what temperatures and pressures copious homogeneous nucleation is expected in the liquid to vapor phase transition. It is also explained why a similar general indication cannot be made for the inverse vapor to liquid transition. Simultaneously, the validity of Peng-Robinson's equation of state [D.-Y. Peng and D. B. Robinson, Ind. Eng. Chem. Fundam. 15, 59 (1976)] is confirmed for highly supersaturated liquids.

de Sá, Elon M.; Meyer, Erich; Soares, Vitorvani

2001-05-01

50

ACA phase calibration scheme with the ALMA water vapor radiometers  

NASA Astrophysics Data System (ADS)

In Atacama Large Millimeter/submillimeter Array (ALMA) commissioning and science verification we have conducted a series of experiments of a novel phase calibration scheme for Atacama Compact Array (ACA). In this scheme water vapor radiometers (WVRs) devoted to measurements of tropospheric water vapor content are attached to ACA’s four total-power array (TP Array) antennas surrounding the 7 m dish interferometer array (7 m Array). The excess path length (EPL) due to the water vapor variations aloft is fitted to a simple two-dimensional slope using WVR measurements. Interferometric phase fluctuations for each baseline of the 7 m Array are obtained from differences of EPL inferred from the two-dimensional slope and subtracted from the interferometric phases. In the experiments we used nine ALMA 12-m antennas. Eight of them were closely located in a 70-m square region, forming a compact array like ACA. We supposed the most four outsiders to be the TP Array while the inner 4 antennas were supposed to be the 7 m Array, so that this phase correction scheme (planar-fit) was tested and compared with the WVR phase correction. We estimated residual root-mean-square (RMS) phases for 17- to 41-m baselines after the planar-fit phase correction, and found that this scheme reduces the RMS phase to a 70 - 90 % level. The planar-fit phase correction was proved to be promising for ACA, and how high or low PWV this scheme effectively works in ACA is an important item to be clarified.

Asaki, Yoshiharu; Matsushita, Satoki; Morita, Koh-Ichiro; Nikolic, Bojan

2012-09-01

51

Vapor-phase exchange of perchloroethene between soil and plants  

USGS Publications Warehouse

Tree core concentrations of tetrachloroethylene (perchloroethene, PCE) at the Riverfront Superfund Site in New Haven, MO, were found to mimic the profile of soil phase concentrations. The observed soil-tree core relationship was stronger than that of groundwater PCE to tree core concentrations at the same site. Earlier research has shown a direct, linear relationship between tree core and groundwater concentrations of chlorinated solvents and other organics. Laboratory-scale experiments were performed to elucidate this phenomenon, including determining partitioning coefficients of PCE between plant tissues and air and between plant tissues and water, measured to be 8.1 and 49 L/kg, respectively. The direct relationship of soil to tree core PCE concentrations was hypothesized to be caused by diffusion between tree roots and the soil vapor phase in the subsurface. The central findings of this research are discovering the importance of subsurface vapor-phase transfer for VOCs and uncovering a direct relationship between soil vapor-phase chlorinated solvents and uptake rates that impact contaminant translocation from the subsurface and transfer into the atmosphere. ?? 2005 American Chemical Society.

Struckhoff, G. C.; Burken, J. G.; Schumacher, J. G.

2005-01-01

52

Bacterial chemotaxis along vapor-phase gradients of naphthalene.  

PubMed

The role of bacterial growth and translocation for the bioremediation of organic contaminants in the vadose zone is poorly understood. Whereas air-filled pores restrict the mobility of bacteria, diffusion of volatile organic compounds in air is more efficient than in water. Past research, however, has focused on chemotactic swimming of bacteria along gradients of water-dissolved chemicals. In this study we tested if and to what extent Pseudomonas putida PpG7 (NAH7) chemotactically reacts to vapor-phase gradients forming above their swimming medium by the volatilization from a spot source of solid naphthalene. The development of an aqueous naphthalene gradient by air-water partitioning was largely suppressed by means of activated carbon in the agar. Surprisingly, strain PpG7 was repelled by vapor-phase naphthalene although the steady state gaseous concentrations were 50-100 times lower than the aqueous concentrations that result in positive chemotaxis of the same strain. It is thus assumed that the efficient gas-phase diffusion resulting in a steady, and possibly toxic, naphthalene flux to the cells controlled the chemotactic reaction rather than the concentration to which the cells were exposed. To our knowledge this is the first demonstration of apparent chemotactic behavior of bacteria in response to vapor-phase effector gradients. PMID:21080701

Hanzel, Joanna; Harms, Hauke; Wick, Lukas Y

2010-12-15

53

Electronic Cigarettes  

MedlinePLUS

... Electronic cigarettes (E-cigarettes) are devices that deliver nicotine to a user by heating and converting to ... of propylene glycol, vegetable glycerin, flavoring chemicals, and nicotine 1 ( Figure ). E-cigarette use doubled in just ...

54

Numerical Modelling of the Expansion Phase of Vapor Explosions  

NASA Astrophysics Data System (ADS)

When a cold liquid is brought into contact with a molten material with a temperature significantly higher than the liquid boiling point, an explosive interaction, involving sudden fragmentation of some of the molten material and rapid evaporation of the liquid, takes place. This phenomenon is referred to as a "vapor explosion" or "steam explosion". In the event of a core meltdown accident in a light water reactor, the molten fuel can interact with cooling water inside or outside the reactor vessel and cause a vapor explosion. The mechanical energy released during such an explosion can result in structural damage, and ultimately may lead to the release of radioactive material into the environment. Vapor explosions are extremely fast transients, involving a flow field consisting of at least three distinct phases, accompanied by thermal non-equilibrium and strong interfacial transfer processes. The objective of this research was to mechanistically model the expansion phase of a vapor explosion. A transient three-dimensional, three -fluid thermal hydraulic model was developed. Coolant liquid plus fragmented fuel particles, coolant vapor plus noncondensables and unfragmented fuel constitute the three fluids. Hydrodynamic and thermal interactions between the three phases were mechanistically treated, using flow regime-dependent models. The models were incorporated into a computer code, in which the conservation equations are cast in finite-difference form and are numerically solved using the point-relaxation method. The code was utilized in parametric and sensitivity calculations aimed at assessing the significance of interfacial transfer processes, and the effect of the premixture initial conditions on the phenomenology of the expansion phase of steam explosions. The initial conditions for the expansion phase were estimated by assuming that the propagation phase was a constant volume heat exchange process. Parametric results indicate that thermal and mechanical nonequilibrium are both significant. Various modelling assumptions relevant to the inter-phase transfer coefficients could change the predicted magnitude of the conversion ratio by up to a factor of two. The parametric results were extremely sensitive to the initial void fraction in the premixture prior to the propagation. The calculated conversion ratios varied by an order of magnitude as a result of varying the aforementioned initial void fraction.

Hwang, Moonkyu

55

Quantitative infrared spectra of vapor phase chemical agents  

Microsoft Academic Search

Quantitative, high resolution (0.1 cm-1) infrared spectra have been acquired for a number of pressure broadened (101.3 KPa N2), vapor phase chemicals including: Sarin (GB), Soman (GD), Tabun (GA), Cyclosarin (GF), VX, nitrogen mustard (HN3), sulfur mustard (HD) and Lewisite (L). The spectra are acquired using a heated, flow-through White cell of 5.6 m optical path length. Each reported spectrum

Steven W. Sharpe; Timothy J. Johnson; Pamela M. Chu; James Kleimeyer; Brad Rowland; Patrick J. Gardner

2003-01-01

56

Synthesis of Chiral Polyaniline Films via Chemical Vapor Phase Polymerization  

Microsoft Academic Search

Electrically and optically active polyaniline films doped with 1R---10-camphorsulfonic acid were successfully deposited on nonconductive substrates via chemical vapor phase polymerization. The above polyaniline\\/R-camphorsulfonate films were characterized by electrochemical and physical methods, such as cyclic voltammetry CV, UV-vis spectroscopy, four-point probe conductivity measurement, Raman spectroscopy, circular dichroism spectroscopy, and scanning electron microscopy. The polyaniline films grown by this method not

Jun Chen; Yingpit Pornputtkul; Keld West; L. Kane-Macguire; Gordon G. Wallace

2006-01-01

57

High-Temperature Vapor Phase Lubrication Using Carbonaceous Gases  

Microsoft Academic Search

Following the pioneering work of Prof. James Lauer, the ability to provide continuous solid lubrication through vapor phase\\u000a delivery of carbonaceous gases has been successfully demonstrated on a pin-on-disk contact at the temperatures of 650 °C.\\u000a Results from tribological experiments under 2 N normal load and 50 mm\\/s sliding speed showed an over 20× reduction in friction\\u000a coefficient. The samples were silicon nitride

Nicolas Argibay; James H. Keith; Brandon A. Krick; D. W. Hahn; Gerald R. Bourne; W. Gregory Sawyer

2010-01-01

58

Superfluid helium 2 liquid-vapor phase separation: Technology assessment  

NASA Technical Reports Server (NTRS)

A literature survey of helium 2 liquid vapor phase separation is presented. Currently, two types of He 2 phase separators are being investigated: porous, sintered metal plugs and the active phase separator. The permeability K(P) shows consistency in porous plug geometric characterization. Both the heat and mass fluxes increase with K(P). Downstream pressure regulation to adjust for varying heat loads and both temperatures is possible. For large dynamic heat loads, the active phase separator shows a maximum heat rejection rate of up to 2 W and bath temperature stability of 0.1 mK. Porous plug phase separation performance should be investigated for application to SIRTF and, in particular, that plugs of from 10 to the minus ninth square centimeters to 10 to the minus eighth square centimeters in conjunction with downstream pressure regulation be studied.

Lee, J. M.

1984-01-01

59

Vapor-phase esterification catalyzed by decationized Y zeolites  

SciTech Connect

The kinetics of acetic acid esterification with ethyl alcohol, in vapor phase, have been studied in the presence of decationized Y zeolite catalysts. Two kinetic models have been considered: a Rideal model and a bimolecular surface reaction model. Both of these models satisfactorily fit the experimental data. The choice of the better model has been made on the basis of the physical significance of the parameters obtained by nonlinear regression analysis of the data. Suggestions are given on the mechanism of the reaction, which appears to be similar to that occurring under homogeneous liquid-phase conditions.

Santacesaria, E.; Gelosa, D.; Danise, P.; Carra, S.

1983-04-01

60

Growth of gallium nitride via iodine vapor phase growth  

NASA Astrophysics Data System (ADS)

Thick layers of gallium nitride have been deposited on 1?m thick MOVPE GaN(0001) thin film substrates using a novel vertical iodine vapor phase epitaxy system. The system features three concentric flow zones that separate the reactant gasses until they reached the substrate. Nitrogen flows through the innermost zone and delivers iodine vapor from an external bubbler to the molten Ga maintained at 1040 °C and GaI to the substrate; high-purity ammonia flows through the outermost zone; and nitrogen flows through the middle zone to prevent reaction between the growth species at the GaI nozzle. Growth rates greater than 75 ?m/hr have been achieved at a V/III ratio of 75. The use of higher V/III ratios resulted in lower growth rates. Optical microscopy of the final growth surfaces revealed spiral hillocks with base diameters as large as 1mm. Increased Ga in the vapor phase resulted in a duplex microstructure containing both hillocks and faceted, oriented crystals overgrowing the hillocks.

Mecouch, W. J.; Reitmeier, Z. J.; Park, J.-S.; Davis, R. F.; Sitar, Z.

2005-05-01

61

Vapor phase release of silicon nanostructures for optomechanics application  

NASA Astrophysics Data System (ADS)

Suspended silicon based nanostructures for optomechanic applications have been successfully fabricated using the Hydrofluoric acid (HF) vapor phase etching technique. In this paper, we demonstrate the fabrication of parallel silicon waveguides with a cross section of 250nm x 220nm, and photonic crystal nanobeam cavities with an air gap as small as 50nm between these released structures. The waveguides have been suspended over a distance of more than 75um. Stiction is a major issue for releasing structures with gaps in the order of tens of nanometers. At the same time, the process has to be gentle due to the small dimensions of the structures involved in the release process. HF vapor etching technique was successfully utilized to etch the 2um thick thermally grown sacrificial silicon oxide layer. This process has an high yield as no liquid is in contact with the structures being released, thus eliminating any kind of liquid flow which typically proves to be a potential destruction source for such small structures. This HF vapor phase etching is a simple and controllable process which completely eliminates the requirement of any kind of sophisticated drying techniques needed with conventional wet etching.

Deotare, Parag B.; Khan, Mughees; Loncar, Marko

2009-02-01

62

Determination of pyridine, 2-picoline, 4-picoline and quinoline from mainstream cigarette smoke by solid-phase extraction liquid chromatography\\/electrospray ionization tandem mass spectrometry  

Microsoft Academic Search

The present paper describes the development and validation of a new reversed-phase liquid chromatography–electrospray ionization tandem mass spectrometric method (RP-HPLC–ESI-MS\\/MS) for simultaneous determination of pyridine, 2-picoline, 4-picoline and quinoline from mainstream cigarette smoke. Liquid–liquid extraction followed by solid-phase extraction was applied to extract the target analytes from cigarette smoke. Baseline chromatographic separation was achieved by utilizing a Zorbax SB-Aq (4.6×150mm,

Subhrakanti Saha; Rajib Mistri; B. C. Ray

2010-01-01

63

Crystal growth from the vapor phase experiment MA-085  

NASA Technical Reports Server (NTRS)

Three vapor transport experiments on multicomponent systems were performed during the Apollo Soyuz mission to determine the effects of microgravity forces on crystal morphology and mass transport rates. The mixed systems used germanium selenide, tellurium, germanium tetraiodide (transport agent), germanium monosulfide, germanium tetrachloride (transport agent), and argon (inert atmosphere). The materials were enclosed in evacuated sealed ampoules of fused silica and were transported in a temperature gradient of the multipurpose electric furnace onboard the Apollo Soyuz spacecraft. Preliminary evaluation of 2 systems shows improved quality of space grown crystals in terms of growth morphology and bulk perfection. This conclusion is based on a direct comparison of space grown and ground based crystals by means of X-ray diffraction, microscopic, and chemical etching techniques. The observation of greater mass transport rates than predicted for a microgravity environment by existing vapor transport models indicates the existence of nongravity caused transport effects in a reactive solid/gas phase system.

Wiedemeir, H.; Sadeek, H.; Klaessig, F. C.; Norek, M.

1976-01-01

64

Development of a membrane-based vapor-phase bioreactor.  

PubMed

A vapor-phase bioreactor has been developed utilizing porous metal membranes in a cylindrical design employing radial flow as opposed to traditional axial flow for the vapor stream. The system was evaluated for the biodegradation of p-xylene (p-xylene) from a water-saturated air stream by Pseudomonas putida ATCC 23973 immobilized onto sand. The biocatalyst was placed in the annular space between two cylindrical, porous stainless-steel membranes. Details of the reactor system are presented along with biological data verifying system performance. The feed flow rate and p-xylene concentration were varied between 60 and 130 cm(3)/min and 15-150 ppm, respectively. Continuous reactor operation was maintained for 80-200 h with removal efficiencies (based onp-xylene disappearance) between 80 and 95%. The effluent concentration histories were compared to determine the operating range of the bioreactor. PMID:18576134

Rouhana, N; Handagama, N; Bienkowski, P R

1997-01-01

65

Liquid-vapor phase boundaries determination by dynamic experimental method  

NASA Astrophysics Data System (ADS)

Shock-induced vaporization of matter under expansion from high energy states is of interest as an experimental method to determine two-phase region boundaries and position of critical point of liquid-vapor transition. High speed of expansion of matter on the boundary leads to formation of the so-called ``boiling wave.'' Intensive heat and mass transfer with hot shocked helium on the boundary give the opportunity to investigate states not only near binodal but also liquid spinodal. Another possibility to achieve near critical point pressures and temperatures is the heating of material by hot driving plasma under launching. This additional heating gives the possibility to achieve temperatures and pressures exceeding critical parameters of tungsten-one of the most refractory metals. New experimental results and issues of such investigation with nickel and tungsten is analyzed in the proposed paper. .

Ternovoi, Vladimir Ya.; Filimonov, Alexander S.; Fortov, Vladimir E.; Kvitov, Sergey V.; Nikolaev, Dmitry N.; Pyalling, Alexei A.

2000-04-01

66

Sensor for distinguishing liquid-vapor phases of superfluid helium  

NASA Technical Reports Server (NTRS)

A small, high-accuracy, rapid-response, low-power-dissipation sensor used in determining the distribution of the liquid and vapor phases of helium in a rocket-borne cryogenic cooler is described. The device, which consists of a 6 mm constantan wire coated for about two-thirds of its length with a superconductor alloy, operates on the basis of the coating's alternation between superconductivity (during immersion in the fluid) and a normal resistive state (during immersion in the vapor). The sensor's response time upon shift from one environment to the other is found to be less than 10 milliseconds. Details of design criteria, and installation of an array of sensors in a flight dewar are also given.

Petrac, D.; Gatewood, J.; Mason, P.

1976-01-01

67

E-cigarettes: promise or peril?  

PubMed

Electronic cigarettes (e-cigarettes) use a heating element to vaporize nicotine and other ingredients, simulating the visual, sensory, and behavioral aspects of smoking without the combustion of tobacco. An ever-growing number of companies around the world manufacture a wide variety of e-cigarette brands, despite scant information on the safety of the ingredients for human inhalation. This article provides an overview of the history, production, and marketing of e-cigarettes, the contents of e-cigarettes and vapor, how they are used, public health concerns, and implications for nursing practice, research, and policy development. PMID:22289406

Riker, Carol A; Lee, Kiyoung; Darville, Audrey; Hahn, Ellen J

2012-03-01

68

Evaluation of biomarkers of exposure to selected cigarette smoke constituents in adult smokers switched to carbon-filtered cigarettes in short-term and long-term clinical studies.  

PubMed

Cigarette smoke is a complex aerosol that includes a gas vapor phase and a particulate phase. Inclusion of activated carbon in the cigarette filter can reduce some of the gas-phase smoke constituents implicated as toxicologically relevant. The present study evaluated exposure to selected gas-phase constituents when adult smokers switched to prototype cigarettes with a highly activated carbon filter. Smokers (N = 160) in two separate studies were randomized to continue to smoke conventional cigarettes (either a 6-mg or 11-mg FTC tar product), to smoke test cigarettes containing carbon filters (comparable tar levels), or to stop smoking. After completing 8 days in controlled smoking conditions (short-term studies), smokers had the option to continue in 24-week long-term ambulatory studies with unrestricted smoking. Urinary excretion of mercapturic acid metabolites of 1,3-butadiene, acrolein, and benzene; nicotine and five of its metabolites, total NNAL, and 1-hydroxypyrene were measured at baseline in the conventional cigarette group, in all groups in the short-term studies, and every 4 weeks in the long-term studies. In the short-term studies, statistically significant reductions (>70%, p<.001) in gas-phase biomarker levels were observed in the test cigarette group for both tar level products compared with the conventional cigarette group. These reductions were similar to those observed in the stop-smoking groups. The reductions continued consistently (p<.001) throughout the long-term studies. Switching to test cigarettes minimally affected the particulate-phase biomarkers. Statistically significant and consistent reductions in selected gas vapor phase biomarkers were observed when smokers switched to activated carbon filter cigarettes. PMID:19023827

Sarkar, Mohamadi; Kapur, Sunil; Frost-Pineda, Kimberly; Feng, Shixia; Wang, Jingzhu; Liang, Qiwei; Roethig, Hans

2008-12-01

69

Simultaneous Vapor Deposition and Phase Separation of Polymer Films  

NASA Astrophysics Data System (ADS)

Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique used predominately to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. The major goal of this research is to force and arrest phase separation of deposited species by co-depositing non-reactive molecules (porogens) with reactive monomers and crosslinkers. We introduce these species during iCVD to force and quench polymer induced phase separation (PIPS) during film growth as a step toward tunable pore-size, density, and morphology. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. Cahn-Hilliard theory predicts that the length scale of phase separation depends on the polymer-porogen interaction energy, the polymerization rate and the species' mobility. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Crosslinkers were introduced to limit the growth of phase separated domains and to provide mechanical support during porogen removal. To elucidate how phase separation competes with polymerization and film growth, deposited films were studied using a combination of electron microscopy, profilometry and spectroscopic techniques.

Tao, Ran; Anthamatten, Mitchell

2012-02-01

70

Cigarette smoke extract increases albumin flux across pulmonary endothelium in vitro  

SciTech Connect

Cigarette smoking causes lung inflammation, and a characteristic of inflammation is an increase in vascular permeability. To determine if cigarette smoke could alter endothelial permeability, we studied flux of radiolabeled albumin across monolayers of porcine pulmonary artery endothelium grown in culture on microporous membranes. Extracts (in either dimethylsulfoxide or phosphate-buffered saline) of cigarette smoke in a range estimate of concentrations simulating cigarette smoke exposure to the lungs in vivo caused a dose-dependent increase in albumin flux that was dependent on extracellular divalent cations and associated with polymerization of cellular actin. The effect was reversible, independent of the surface of endothelial cells exposed (either luminal or abluminal), and due primarily to components of the vapor phase of smoke. The effects occurred without evidence of cell damage, but subtle morphological changes were produced by exposure to the smoke extracts. These findings suggest that cigarette smoke can alter permeability of the lung endothelium through effects on cytoskeletal elements.

Holden, W.E.; Maier, J.M.; Malinow, M.R.

1989-01-01

71

Healing defective CVD-graphene through vapor phase treatment  

NASA Astrophysics Data System (ADS)

Structural defects present on chemical vapor deposition (CVD)-graphene have usually originated from the growth stage and transfer process. They limit the electronic transport properties of graphene and degrade performance of related devices. Here we report that these inherent atomic defects could be selectively healed by a simple vapor phase treatment performed in equipment conventionally used for atomic layer deposition (ALD). The unique chemistry of Al2O3 ALD facilitated selective depositions of AlxOy compounds on the defects, which could be readily probed and visualized using AFM imaging. The healing agent, AlxOy, was observed to bind tightly to the defects and lead to doping of the CVD-graphene, which was reflected in the noticeable improvement in electrical sheet resistance. In contrast with the chemically doped graphene, the ALD-treated graphenes revealed notable long-term stability under environmental conditions. Our approach promises selective healing of defects present in most materials and possibly ensures considerable improvement in electrical and mechanical properties. ALD with a broad spectrum of material selection could be a versatile tool for upgrading properties of materials.Structural defects present on chemical vapor deposition (CVD)-graphene have usually originated from the growth stage and transfer process. They limit the electronic transport properties of graphene and degrade performance of related devices. Here we report that these inherent atomic defects could be selectively healed by a simple vapor phase treatment performed in equipment conventionally used for atomic layer deposition (ALD). The unique chemistry of Al2O3 ALD facilitated selective depositions of AlxOy compounds on the defects, which could be readily probed and visualized using AFM imaging. The healing agent, AlxOy, was observed to bind tightly to the defects and lead to doping of the CVD-graphene, which was reflected in the noticeable improvement in electrical sheet resistance. In contrast with the chemically doped graphene, the ALD-treated graphenes revealed notable long-term stability under environmental conditions. Our approach promises selective healing of defects present in most materials and possibly ensures considerable improvement in electrical and mechanical properties. ALD with a broad spectrum of material selection could be a versatile tool for upgrading properties of materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00775a

van Lam, Do; Kim, Sang-Min; Cho, Youngji; Kim, Jae-Hyun; Lee, Hak-Joo; Yang, Jun-Mo; Lee, Seung-Mo

2014-05-01

72

Continuous Determination of High-Vapor Phase Concentrations of Tetrachloroethylene Using On-Line Mass Spectrometry  

EPA Science Inventory

A method was developed to determine the vapor concentration of tetrachloroethylene (PCE) at and below its equilibrium vapor phase concentration, 168,000 µg/L (25°C). Vapor samples were drawn by vacuum into a six-port sampling valve and injected through a jet separator into an io...

73

Evidence of Phase Separation during Vapor Deposition Polymerization  

NASA Astrophysics Data System (ADS)

Initiated chemical vapor deposition (iCVD) is a solventless, free radical technique predominately used to deposit homogeneous films of linear and crosslinked polymers directly from gas phase feeds. We are developing multicomponent iCVD techniques to induce phase separation during film growth. Small molecule porogens and crosslinkers are introduced into the iCVD process during film growth of poly(glycidyl methacrylate). Analogous to well established polymerization induced phase separation (PIPS) processes, porogens, such as dimethyl phthalate, are well mixed at the growing gas-film interface but are immiscible with high molecular weight polymer. Polymerization, crosslinking and PIPS are intended to occur simultaneously on the substrate, resulting in a vitrified microstructure. A series of films were grown by varying deposition rate, porogen type, and reagent flowrates. Deposited films were studied by electron microscopy and spectroscopic techniques. Experiments are compared to Cahn-Hilliard theory predictions that relate the length and time scale of the phase separation to the polymer-porogen interaction energy, the rate of polymerization and the species mobility.

Tao, Ran; Anthamatten, Mitchell

2013-03-01

74

Menthol Cigarettes  

MedlinePLUS

... past, the tobacco industry has a history of marketing menthol cigarettes to women, youth, and minority racial/ ... Sutton, C.D. and R.G. Robinson, The marketing of menthol cigarettes in the United States: populations, ...

75

Healing defective CVD-graphene through vapor phase treatment.  

PubMed

Structural defects present on chemical vapor deposition (CVD)-graphene have usually originated from the growth stage and transfer process. They limit the electronic transport properties of graphene and degrade performance of related devices. Here we report that these inherent atomic defects could be selectively healed by a simple vapor phase treatment performed in equipment conventionally used for atomic layer deposition (ALD). The unique chemistry of Al2O3 ALD facilitated selective depositions of AlxOy compounds on the defects, which could be readily probed and visualized using AFM imaging. The healing agent, AlxOy, was observed to bind tightly to the defects and lead to doping of the CVD-graphene, which was reflected in the noticeable improvement in electrical sheet resistance. In contrast with the chemically doped graphene, the ALD-treated graphenes revealed notable long-term stability under environmental conditions. Our approach promises selective healing of defects present in most materials and possibly ensures considerable improvement in electrical and mechanical properties. ALD with a broad spectrum of material selection could be a versatile tool for upgrading properties of materials. PMID:24756318

Van Lam, Do; Kim, Sang-Min; Cho, Youngji; Kim, Jae-Hyun; Lee, Hak-Joo; Yang, Jun-Mo; Lee, Seung-Mo

2014-06-01

76

Quantitative Fourier Transform Infrared Analysis of Gas Phase Cigarette Smoke and Other Gas Mixtures  

Microsoft Academic Search

A new method for the analysis of selected components in complex gas mixtures has been developed utilizing a relatively inexpensive Fourier transform infrared spectrometer and a continuous flow gas cell. the method was used to monitor nitric oxide and nitrogen dioxide concentrations in cigarette smoke with time.Using multivariate least-square regression analysis, it is possible to simultaneously quantitate both NO and

Rafael Cueto; Daniel R. Church; William A. Piyor

1989-01-01

77

Quantitative infrared spectra of vapor phase chemical agents  

NASA Astrophysics Data System (ADS)

Quantitative, high resolution (0.1 cm-1) infrared spectra have been acquired for a number of pressure broadened (101.3 KPa N2), vapor phase chemicals including: Sarin (GB), Soman (GD), Tabun (GA), Cyclosarin (GF), VX, nitrogen mustard (HN3), sulfur mustard (HD) and Lewisite (L). The spectra are acquired using a heated, flow-through White cell of 5.6 m optical path length. Each reported spectrum represents a statistical fit to Beer"s law, which allows for a rigorous calculation of uncertainty in the absorption coefficients. As part of an ongoing collaboration with the National Institute of Standards and Technology (NIST), cross-laboratory validation is a critical aspect of this work. In order to identify possible errors in the Dugway flow-through system, quantitative spectra of isopropyl alcohol from both NIST and Pacific Northwest National Laboratory (PNNL) are compared to similar data taken at the Dugway Proving Ground (DPG).

Sharpe, Steven W.; Johnson, Timothy J.; Chu, Pamela M.; Kleimeyer, James; Rowland, Brad

2003-08-01

78

Filling of carbon nanotubes with selenium by vapor phase process.  

PubMed

A vapor phase method was developed to fill different kinds of nanotubes (including multiwall and singlewall nanotubes), which inner diameters range from 200 down to 1.5 nm. Experiments were performed with selenium in a sealed reactor in order to control the selenium partial pressure. This process allows a full control of the nanotube filling (partial or complete), i.e., either a selective diameter filling or a full filling rate. The weight gain of all the samples was plotted for different reaction temperature as a function of selenium pressure. Experimental isotherms are characteristic of capillary condensation of selenium, which occurs at first in the smallest nanotube inner diameters. X-ray diffraction data show that selenium confined in nanotubes with diameters larger than 3 nm keeps its trigonal structure. PMID:16573074

Chancolon, Jérôme; Archaimbault, Françoise; Pineau, Alain; Bonnamy, Sylvie

2006-01-01

79

A High Temperature Vapor Phase Lubrication Study Utilizing a Thioether Liquid Lubricant  

NASA Technical Reports Server (NTRS)

Much of the experimental work on vapor phase lubrication has employed certain organo phosphorous compounds as the vapor phase lubricant. Graham and Klaus, for instance, used tricresyl phosphate (TCP) and tributyl phosphate to vapor phase lubricate a four-ball wear tester using M50 steel balls at 370 C. Makki and Graham were able to vapor phase lubricate a reciprocating pin on plate tribometer using 1018 steel at 280 C with TCP vapor. Although a few organo phosphorous compounds, such as TCP, have been successfully used as vapor phase lubricants in many laboratory experiments, many problems remain unsolved. Two areas of concern relate to the 'durability' of phosphate deposited films and to the ability of the lubricating system to "self-recover" when vapor phase lubricated with an organo phosphorous compound. Durability refers to the ability of the deposited film to provide effective lubrication, for a period of time, after the vapor flow to the lubricating surfaces has been interrupted. Vapor phase lubrication tests, conducted at Cleveland State University with their high temperature tribometer, revealed that when TCP vapor flow to the lubricating surfaces was interrupted the frictional coefficient of the system rapidly increased from a value less than 0.1 to a value of 0.3 which was selected as our failure point. Self-recovery means the ability of the vapor phase lubricant to reduce the frictional coefficient of the lubricating system back down to value less than 0.1 after startup of the interrupted vapor flow. Lubrication tests conducted at Cleveland State University revealed that the high temperature tribometer could not self-recover after startup of the interrupted TCP vapor flow.

Morales, Wilfredo; Graham, E. Earl; Galvin, Thomas

1997-01-01

80

Field demonstration of vapor phase TCE bioreactor. Final report  

SciTech Connect

The objective of this Cooperative Research and Development Agreement (CRADA), was to demonstrate the effectiveness of a vapor-phase bioreactor system for the destruction of trichloroethylene (TCE) from contaminated groundwater. A field demonstration was per-formed using groundwater at the Oak Ridge K-25 Site contaminated with a complex mixture of organic chemicals. This site is managed and operated by Martin Marietta Energy Systems, Inc. for the Department of Energy (DOE). Analysis of the data generated during the test can be summarized in three major observations. First, TCE was degraded in the presence of all the organics found in the steam strip condensate. This was observed during treatment of both the steam strip condensate and condensate amended with TCE to increase its concentration relative to the other components. The conclusion that TCE was being biodegraded was supported by performing mass balance control experiments with the reactor and by tracking recalcitrant chemicals also present in the steam stripper condensate. Second, there appeared to be an initial lag period of up to 24 hours before onset of TCE degradation in the reactor. The source of this lag was not determined but could be related to either an acclimation of the microorganisms to other chemicals found in the condensate or reversible inhibitory effects on TCE degradation. The duration of TCE degradative activity was relatively short for only 2 to 5 days. compared to previous demonstrations where TCE was the sole contaminant. However, several of the runs were interrupted due to mechanical and not biological issues. Third, other chemical contaminants were also degraded. by the bacteria used in the vapor phase reactor which is consistent with previous work performed both at ENVIROGEN and elsewhere.

NONE

1994-12-14

81

Airborne and vapor phase hydrocarbons over the Mediterranean Sea  

SciTech Connect

n-Alkane distributions and concentrations have been determined in the atmospheric particulate and gas phases for samples collected over the Mediterranean Sea. Distributions of airborne alkanes exhibited a strong odd to even predominance in the C{sub 22}-C{sub 38} range associated with the presence of unresolved compounds indicating a mixture of terrigenous and anthropogenic inputs. Variations in their concentration levels could be related to the origin of air masses. Solvent extractable gas phase n-alkanes dominated in the C{sub 15}-C{sub 22} range with a slight predominance of n-C{sub 17} except in one sample were C{sub 18} and C{sub 20} were dominant. A hump of unresolved compounds shifted toward low molecular weight was observed in all the samples. The origin of vapor phase hydrocarbons is discussed with respect to the composition of seawater samples collected during the same cruise. From lifetime and transport time considerations as well as distribution features, both marine and continental origins, as distribution features, both marine and continental origins, likely anthropogenic, are suggested. The strong terrigenous signal of the suspended particles in the microlayer and underlying waters is attributed to aerosol deposition. The dissolved alkane compositional feature suggested both marine and anthropogenic sources.

Marie-Alexandrine, S.; Jean-Claude, M.; Anne, L.; Alain, S.

1990-11-01

82

Possible existence of platelet aggregation inhibitor(s) in a gas-phase extract of cigarette smoke.  

PubMed

Present study demonstrated an existence of anti-aggregation factor(s) in water-soluble extract of a gas-phase of cigarette smoke, and studied chemical characteristics of the factor(s) evaluating its inhibitory potency on platelet aggregation of human and rabbit platelets. The water-soluble extract was prepared by passing mainstream smoke of one cigarette through a Cambridge glassfiber filter and then bubbling it through 1 ml of water. The inhibitory effects were similar in both human and rabbit platelets with the final concentrations of 1 to 5% of the aqueous extract, and were also non-specific irrespective of types of agonists such as collagen, arachidonic acid, STA2 (a stable analogue of thromboxane A2), ADP or nor-adrenaline. The inhibitory effect of water-soluble extract on platelet aggregation were not affected by treatment of the extract by erythrocytes, indicating that the factor(s) was different from the one that is adsorbed by hemoglobin, such as superoxide radicals, nitric oxide (NO), nitrogen oxides (Nox), hydrogen peroxide (H2O2), carbon monoxide (CO), aldehydes, trace elements (Cd2+, Cu2+) or carcinogenic nitrosocompounds. The inhibitor(s) was stable in acidic condition under 4 degrees C but unstable in basic condition under room temperature. The anti-platelet factor(s) was retained on a reversed phase chromatography column, and eluted with 50 to 60% methanol. The substance(s) was also adsorbed by H+ and OH- form ion exchange columns, but not by Cl- form, suggesting that the substance is both basic and acidic but not so strong as to be absorbed by Cl- form column. These facts suggest that the anti-platelet substance(s) in the water extract of cigarette smoke seems to be moderately non polar, both acidic and basic in water and not adsorbed by hemoglobin. PMID:9431780

Takano, S; Matsuoka, I; Magami, W; Watanabe, C; Nakanishi, H

1997-06-01

83

Simultaneous Heat and Momentum Transfer in Two-Phase Systems at Low Pressure and High Temperature: Vapor Phase  

Microsoft Academic Search

The heat and momentum transfer in a liquid-vapor two-phase film system at high temperature and low pressure is studied by the example of the removal of highly volatile fractions from high-boiling liquids in film evaporators. The temperature and velocity distributions in the vapor phase are determined.

V. N. Babak

2005-01-01

84

Quantitative Fourier transform infrared analysis of gas phase cigarette smoke and other gas mixtures  

SciTech Connect

A new method for the analysis of selected components in complex gas mixtures has been developed utilizing a relatively inexpensive Fourier transform infrared spectrometer and a continuous flow gas cell. The method was used to monitor nitric oxide and nitrogen dioxide concentrations in cigarette smoke with time. Using multivariate least-square regression analysis, it is possible to simultaneously quantitate both NO and NO{sub 2}, even in the presence of overlapping peaks. Using this method, the oxidation of nitric oxide in the presence of isoprene in cigarette smoke and in a model system was followed with time. The method also can be applied to other compounds in smoke or to any other gaseous mixture.

Cueto, R.; Church, D.F.; Pryor, W.A. (Louisiana State Univ., Baton Rouge (USA))

1989-03-01

85

Determination of oxides of nitrogen (NO\\/sub x\\/) in cigarette smoke by chemiluminescent analysis  

Microsoft Academic Search

The successful application of a commercial chemiluminescent No\\/sub x\\/ analyzer to the determination of oxides of nitrogen in cigarette smoke is reported. Individual puffs of the smoke vapor phase are rapidly diluted in an air stream before introduction into the analyzer. This acts to both reduce quenching of the chemiluminescent response by COâ and to prevent side reactions of the

R. A. Jenkins; B. E. Gill

1980-01-01

86

Chemical composition of cigarette smoke  

Microsoft Academic Search

Cigarette smoke is a concentrated aerosol of liquid particles suspended in an atmosphere consisting mainly of nitrogen, oxygen, and carbon dioxide. While the precise chemical composition of the particulate and gaseous phases is dependent on the characteristics of the cigarette and the manner in which it is smoked, both phases contain tens of hundreds of individual constitutents. Notable among potentially

Guerin

1979-01-01

87

Could charcoal filtration of cigarette smoke reduce smoking-induced disease? A review of the literature.  

PubMed

A review of the published work with charcoal-filtered cigarettes indicates that there are reductions in the concentrations for many gas-vapor phase constituents found in mainstream smoke. However, charcoal filters provided no apparent capacity for reduction of smoke particulate phase components. The reductions in gas-vapor phase smoke chemistry analytes generally correspond with findings of reduced toxicological activity, principally related to a reduction in the cytotoxic action of the volatile smoke constituents. Results of a short-term clinical study show small reductions in the biomarkers of the gas-vapor phase smoke constituents in subjects smoking charcoal-filtered cigarettes, compared to subjects smoking non-charcoal filtered cigarettes. The very limited epidemiology data (a single study) fail to demonstrate a conclusive beneficial effect of charcoal-filtered cigarette products compared to non-charcoal filtered cigarette products. Review of the scientific literature is hindered due to the lack of documentation regarding the activity of the charcoal used in the filter, and the inconsistency in product designs used between the various different disciplines (chemistry, pre-clinical, clinical and epidemiology) that have conducted studies with charcoal filtered cigarettes. There do not appear to be any published studies using a combination of data from the different disciplines based on a consistently designed charcoal cigarette filter. Although the literature presently available would suggest that smoke filtration provided by current charcoal filter techniques alone may not be substantial enough to reduce smoking-related disease, the data are limited. Therefore, for the reduction of smoking-induced disease, it is difficult to come to a definitive conclusion regarding the potential health benefits of using charcoal as a smoke filtration technology. PMID:18289753

Coggins, Christopher R E; Gaworski, Charles L

2008-04-01

88

The nuclear liquid-vapor phase transition: Equilibrium between phases or free decay in vacuum?  

SciTech Connect

Recent analyses of multifragmentation in terms of Fisher's model and the related construction of a phase diagram brings forth the problem of the true existence of the vapor phase and the meaning of its associated pressure. Our analysis shows that a thermal emission picture is equivalent to a Fisher-like equilibrium description which avoids the problem of the vapor and explains the recently observed Boltzmann-like distribution of the emission times. In this picture a simple Fermi gas thermometric relation is naturally justified. Low energy compound nucleus emission of intermediate mass fragments is shown to scale according to Fisher's formula and can be simultaneously fit with the much higher energy ISiS multifragmentation data.

Phair, L.; Moretto, L.G.; Elliott, J.B.; Wozniak, G.J.

2002-11-14

89

Effect of cigarette tar content and smoking habits on respiratory symptoms in women.  

PubMed

Standardized respiratory disease questionnaires (ATS-DLD-78) were administered to 5,686 adult women. Risk factors were evaluated by logistic analysis that adjusted for multiple potential confounding factors. Among current smokers, the number of cigarettes smoked per day was consistently the strongest risk factor for chronic cough, chronic phlegm, wheeze, and dyspnea. The odds ratios for these symptoms in a smoker of 25 or more cigarettes per day relative to a smoker of 1--14 cigarettes per day were 4.74, 4.21, 2.05, and 3.71, respectively. Ex-smokers showed risks between those of current and never smokers. Cigarette tar content was a significant independent risk factor for chronic cough (p = 0.005) and of borderline significance for chronic phlegm (p = 0.077). High tar cigarette smokers in this population (average, 22 mg) had an odds ratio of 2.01 for chronic cough and 1.59 for chronic phlegm relative to low tar cigarette smokers (average, 7 mg). The effect of cigarette tar was linear and independent of cigarettes smoked per day. Smoke inhalation was a significant risk factor for chronic cough (p = 0.029) and for chronic phlegm (p = 0.038). Tar content and smoke inhalation were not significant risk factors for wheeze or dyspnea. Cigarette particulate content (tar) appears to be causally linked to cough and phlegm production., but the association of cigarette smoking and symptoms of wheeze and dyspnea may be more strongly related to the vapor phase of cigarette smoke. PMID:7091875

Schenker, M B; Samet, J M; Speizer, F E

1982-06-01

90

Determination of oxides of nitrogen (NO/sub x/) in cigarette smoke by chemiluminescent analysis  

SciTech Connect

The successful application of a commercial chemiluminescent No/sub x/ analyzer to the determination of oxides of nitrogen in cigarette smoke is reported. Individual puffs of the smoke vapor phase are rapidly diluted in an air stream before introduction into the analyzer. This acts to both reduce quenching of the chemiluminescent response by CO/sub 2/ and to prevent side reactions of the NO/sub x/ with vapor phase organic constituents. Sweeping the dilute smoke through a reduced silver-ion exchange resin bed removed a substantial positive interference from hydrogen cyanide. A range of deliveries of 3 to 47 ..mu..mol of NO/sub x/ per cigarette was observed for nine types of experimental cigarettes. Statistically significant differences between NO/sub x/ and NO levels (NO/sub x/ - NO = NO/sub 2/) in smoke were observed in only one type of cigarette, presumably due to large cigarette-to-cigarette variability in constituent deliveries. 2 figures, 3 tables.

Jenkins, R.A.; Gill, B.E.

1980-05-01

91

Limit of Metastability for Liquid and Vapor Phases of Water  

NASA Astrophysics Data System (ADS)

We report the limits of superheating of water and supercooling of vapor from Monte Carlo simulations using microscopic models with configurational enthalpy as the order parameter. The superheating limit is well reproduced. The vapor is predicted to undergo spinodal decomposition at a temperature of Tspvap=46±10 °C (0 °C ?Tspvap?100 °C) under 1 atm. The water-water network begins to form at the supercooling limit of the vapor. Three-dimensional water-water and cavity-cavity unbroken networks are interwoven at critically superheated liquid water; if either network breaks, the metastable state changes to liquid or vapor.

Cho, Woo Jong; Kim, Jaegil; Lee, Joonho; Keyes, Thomas; Straub, John E.; Kim, Kwang S.

2014-04-01

92

Irritants in cigarette smoke plumes.  

PubMed Central

Concentrations of the irritants formaldehyde and acrolein in side stream cigarette smoke plumes are up to three orders of magnitude above occupational limits, readily accounting for eye and nasal irritation. "Low-tar" cigarettes appear at least as irritating as other cigarettes. More than half the irritant is associated with the particulate phase of the smoke, permitting deposition throughout the entire respiratory tract and raising the issue of whether formaldehyde in smoke is associated with bronchial cancer.

Ayer, H E; Yeager, D W

1982-01-01

93

Nanostructure-based optoelectronic sensing of vapor phase explosives - a promising but challenging method  

NASA Astrophysics Data System (ADS)

Optoelectronic sensing of gas phase hazardous chemicals is a newly explored field, which shows great advantages towards low concentration sensing when compared to normal gas sensing in the dark. Here, based on the recent progress on nanostructured vapor phase explosive gas sensors operated in dark conditions, the attractiveness of developing optoelectronic sensors for vapor phase explosive detection was highlighted. Furthermore, we try to propose some new insights to enhance optoelectronic sensing of vapor phase explosives. We suggest employing photocatalysis principles to enhance the sensitivity and employing a molecular imprinting technique (MIT) to enhance the selectivity.

Zu, Baiyi; Guo, Yanan; Dou, Xincun

2013-10-01

94

Thin film solar cells grown by organic vapor phase deposition  

NASA Astrophysics Data System (ADS)

Organic solar cells have the potential to provide low-cost photovoltaic devices as a clean and renewable energy resource. In this thesis, we focus on understanding the energy conversion process in organic solar cells, and improving the power conversion efficiencies via controlled growth of organic nanostructures. First, we explain the unique optical and electrical properties of organic materials used for photovoltaics, and the excitonic energy conversion process in donor-acceptor heterojunction solar cells that place several limiting factors of their power conversion efficiency. Then, strategies for improving exciton diffusion and carrier collection are analyzed using dynamical Monte Carlo models for several nanostructure morphologies. Organic vapor phase deposition is used for controlling materials crystallization and film morphology. We improve the exciton diffusion efficiency while maintaining good carrier conduction in a bulk heterojunction solar cell. Further efficiency improvement is obtained in a novel nanocrystalline network structure with a thick absorbing layer, leading to the demonstration of an organic solar cell with 4.6% efficiency. In addition, solar cells using simultaneously active heterojunctions with broad spectral response are presented. We also analyze the efficiency limits of single and multiple junction organic solar cells, and discuss the challenges facing their practical implementations.

Yang, Fan

95

Numerical Modeling of Liquid-Vapor Phase Change  

NASA Technical Reports Server (NTRS)

We implemented a two- and three-dimensional finite difference/front tracking technique to solve liquid-vapor phase change problems. The mathematical and the numerical features of the method were explained in great detail in our previous reports, Briefly, we used a single formula representation which incorporated jump conditions into the governing equations. The interfacial terms were distributed as singular terms using delta functions so that the governing equations would be the same as conventional conservation equations away from the interface and in the vicinity of the interface they would provide correct jump conditions. We used a fixed staggered grid to discretize these equations and an unstructured grid to explicitly track the front. While in two dimensions the front was simply a connection of small line segments, in three dimensions it was represented by a connection of small triangular elements. The equations were written in conservative forms and during the course of computations we used regriding to control the size of the elements of the unstructured grid. Moreover, we implemented a coalescence in two dimensions which allowed the merging of different fronts or two segments of the same front when they were sufficiently close. We used our code to study thermocapillary migration of bubbles, burst of bubbles at a free surface, buoyancy-driven interactions of bubbles, evaporation of drops, rapid evaporation of an interface, planar solidification of an undercooled melt, dendritic solidification, and a host of other problems cited in the reference.

Esmaeeli, Asghar; Arpaci, Vedat S.

2001-01-01

96

Improved vapor-phase deposition technique for antistiction monolayers  

NASA Astrophysics Data System (ADS)

We have developed an improved vapor-phase deposition method and an apparatus for the wafer-scale coating of monolayer films typically used in anti-stiction applications. The method consists of a surface preparation step using an O2 plasma followed by the tunable deposition of a monolayer film in the same reactor. This process has been successfully applied to MEMS test structures and has demonstrated superior anti-stiction performance. The deposition process allows tuning of the film properties by the precise metering of the precursor and a catalyst as part of the process control scheme. The anti-stiction monolayer film deposited from dimethyldichlorosilane (DDMS), tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS), and heptadecafluoro-1,1,2,2-tetrahydrodecyltrichlorosilane (FDTS) were characterized using contact angle analysis, atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The coefficient of static friction was measured using a sidewall test device and the work of adhesion using a cantilever beam array. The results showed that excellent quality, uniformity, and reproducibility could be achieved across a whole wafer using this method and equipment.

Ashurst, Robert W.; Carraro, Carlo; Chinn, Jeff D.; Fuentes, Victor; Kobrin, Boris; Maboudian, Roya; Nowak, Romuald; Yi, Richard

2004-01-01

97

Scavenging of free radicals in gas-phase mainstream cigarette smoke by immobilized catalase at filter level.  

PubMed

Catalase is well known as capable of inducing the decomposition of H(2)O(2). In this study, a kind of immobilized catalase (entrapped in cross-linked chitosan beads) was dispersed in conventional acetate filter as an antioxidant additive. Quantitative estimation of the free radicals in mainstream cigarette smoke (MCS) was performed to address the effect of this modified filter. It was found that the levels of PBN adduct and NO(*)/NO(2)(*) associated with the gas-phase mainstream cigarette smoke (GPCS) were efficiently decreased by approximately 40% through catalase filtering. Besides, the modified filter was found to lower the MCS-induced adverse biological effects including lipid peroxidation and mutagenicity. This was proved to be substantially attributed to the catalase-dependent breakdown of NO(*), which was stimulated by some of peroxides (most probably being H(2)O(2)), the dismutation products of tar particulate matters (TPM). These results highlighted a promising approach to reduce the smoking-associated health risks to passive smokers. Moreover, the mechanisms of catalase filtering may be helpful for the development of appropriate immobilized enzyme systems to be applied for reducing health risks associated with gaseous pollutants. PMID:18344119

Lu, Xin; Hua, Zhaozhe; Du, Guocheng; Ma, Xiaolong; Cao, Jianhua; Yang, Zhanping; Chen, Jian

2008-03-01

98

Gas Phase Analysis of Diamond Growth Chemical Vapor Deposition Systems.  

NASA Astrophysics Data System (ADS)

The gas composition of two diamond film chemical vapor deposition (CVD) systems is probed with absorption spectroscopy. The gas temperature in a hot filament diamond CVD system is derived from the vacuum ultraviolet absorption spectrum of the H_2 molecule using synchrotron continuum radiation. The gas temperature is influenced most strongly by the substrate temperature, less strongly by heat conduction from the filament, and is nearly unaffected by heat deposited or absorbed by chemical reactions. The density of methyl radicals (CH _3) and the mole fraction of acetylene are measured in a hot filament CVD system both during and after an initial pretreatment that is intended to enhance the crystal nucleation density. The measurements suggest that the surface condition of the filament is the primary factor affecting the gas phase chemistry both during and after the pretreatment. The densities of CH_3 and CH and the hydrogen dissociation fraction are measured in a hot filament diamond CVD system for each of five different hydrocarbon input gases. The crystal growth rate and morphology of the diamond grown from the different input gases are also examined. The results indicate that the nature of the input hydrocarbon is relatively unimportant, and that the addition of oxygen greatly alters the gas phase chemistry and the filament surface condition. The absolute column densities of CH_3 and CH and the hydrogen dissociation ratio are measured in a DC hollow cathode plasma-assisted CVD system. The plasma gas temperature is determined using the H _2 emission spectrum near 460 nm. The CH _3 and CH densities are compared with measurements made in the hot filament CVD system.

Menningen, Kenneth Lee

1995-01-01

99

Calibration of an explosives vapor generator based on vapor diffusion from a condensed phase  

SciTech Connect

Development of a vapor generator for consistently producing accurate amounts of vapor from low vapor pressure explosive materials is a pressing need within the explosives detection community. Of particular importance for reproducibility and widespread acceptance of results is the correlation of such a vapor generator to a National Institute of Standards and Technology (NIST) mass standard. This paper describes an explosives vapor generator recently developed at Varian in which a solid explosive sample in a precision bore glass tube is put in an oven at constant temperature, and vapor diff-using from the top of the tube is entrained in a carrier gas flow. The rate of vapor output is thus dependent on both the equilibrium vapor pressure of the solid at oven temperature and the rate of diffusion up the length of the tube. Correlation to a NIST mass standard is achieved by periodic weighing of the sample tube on a microbalance. We report results obtained with the explosives TNT and RDX. Results for TNT show that the mass output rate is constant over hundreds of hours of continuous use, with outputs of {approximately} 10--2000 pg/sec for oven temperatures in the range of 60--120{degrees}C. Both the mass loss experiments and calibration with an ion mobility spectrometer (IMS) give a TNT mass output value of 85 pg/sec at 79{degrees}C, and this result is supported by transport theory calculations. Mass loss curves for RDX are also linear with time, and show the expected exponential increase of mass output with oven temperature.

Parmeter, J.E.; Rhykerd, L. Jr.; Conrad, F.J. [Sandia National Labs., Albuquerque, NM (United States); Tiano, G.S.; Preston, D.; Eiceman, G.A. [New Mexico State Univ., Las Cruces, NM (United States). Dept. of Chemistry and Biochemistry; Arnold, J.T. [Varian Associates, Palo Alto, CA (United States). Ginzton Research Laboratory

1995-12-31

100

VALIDATION OF CHEMICAL AND BIOLOGICAL TECHNIQUES FOR EVALUATION OF VAPORS IN AMBIENT AIR/MUTAGENICITY TESTING OF TWELVE (12) VAPOR-PHASE COMPOUNDS  

EPA Science Inventory

The overall objective of this research was to further validate Ames mutagenicity preincubation system for detection of vapors in ambient air. Parametes for detection of vapors in the Ames/Salmonella mutagenicity assay were investigated and 12 vapor-phase compounds were tested for...

101

Synthesis and characterization of nano-scale aluminum nitride produced from vapor phase  

Microsoft Academic Search

Nano-scale AlN particles were synthesized from the vapor phase using ammonia and aluminum chloride vapor as reactants. The apparatus consists of vaporization system, ammonia distributor, tubular synthesis reactor and powder collection system. The aluminum nitride nucleates and grows along the reactor length. The AlN powder produced was collected and chemically and physically characterized. For microstructural and microchemical characterization, X-ray diffractograms

B. C. Di Lello; F. J. Moura; I. G. Solórzano

2001-01-01

102

Use of electronic cigarettes (e-cigarettes) impairs indoor air quality and increases FeNO levels of e-cigarette consumers.  

PubMed

Despite the recent popularity of e-cigarettes, to date only limited data is available on their safety for both users and secondhand smokers. The present study reports a comprehensive inner and outer exposure assessment of e-cigarette emissions in terms of particulate matter (PM), particle number concentrations (PNC), volatile organic compounds (VOC), polycyclic aromatic hydrocarbons (PAH), carbonyls, and metals. In six vaping sessions nine volunteers consumed e-cigarettes with and without nicotine in a thoroughly ventilated room for two hours. We analyzed the levels of e-cigarette pollutants in indoor air and monitored effects on FeNO release and urinary metabolite profile of the subjects. For comparison, the components of the e-cigarette solutions (liquids) were additionally analyzed. During the vaping sessions substantial amounts of 1,2-propanediol, glycerine and nicotine were found in the gas-phase, as well as high concentrations of PM2.5 (mean 197?g/m(3)). The concentration of putative carcinogenic PAH in indoor air increased by 20% to 147ng/m(3), and aluminum showed a 2.4-fold increase. PNC ranged from 48,620 to 88,386 particles/cm(3) (median), with peaks at diameters 24-36nm. FeNO increased in 7 of 9 individuals. The nicotine content of the liquids varied and was 1.2-fold higher than claimed by the manufacturer. Our data confirm that e-cigarettes are not emission-free and their pollutants could be of health concern for users and secondhand smokers. In particular, ultrafine particles formed from supersaturated 1,2-propanediol vapor can be deposited in the lung, and aerosolized nicotine seems capable of increasing the release of the inflammatory signaling molecule NO upon inhalation. In view of consumer safety, e-cigarettes and nicotine liquids should be officially regulated and labeled with appropriate warnings of potential health effects, particularly of toxicity risk in children. PMID:24373737

Schober, Wolfgang; Szendrei, Katalin; Matzen, Wolfgang; Osiander-Fuchs, Helga; Heitmann, Dieter; Schettgen, Thomas; Jörres, Rudolf A; Fromme, Hermann

2014-07-01

103

Solid\\/liquid- and vapor-phase interactions between cellulose- and lignin-derived pyrolysis products  

Microsoft Academic Search

Solid\\/liquid- and vapor-phase interactions between cellulose- and lignin (Japanese cedar milled wood lignin)-derived pyrolysis products were studied under the conditions of N2\\/600°C\\/40–80s. A dual-space closed ampoule reactor was used to eliminate the solid\\/liquid-phase interactions, and careful comparison of the resulting data with those of the pyrolysis of the mixed samples gave some insights into the solid\\/liquid- and vapor-phase interactions separately.

Takashi Hosoya; Haruo Kawamoto; Shiro Saka

2009-01-01

104

A Numerical Method for Multiphase Incompressible Thermal Flows with Solid-Liquid and Liquid-Vapor Phase Transformations  

Microsoft Academic Search

A numerical method for multiphase incompressible thermal flows with solid–liquid and liquid–vapor phase transformations is presented. The flow is mainly driven by thermocapillary force and vaporization. Based on the level set method and mixture continuum model, a set of governing equations valid for solid, liquid, and vapor phases is derived, considering phase boundary conditions as source terms in the transport

Hyungson Ki; Pravansu S. Mohanty; Jyoti Mazumder

2005-01-01

105

Reduction of the proteolytic activity of neutrophils by exposure to cigarette smoke in vitro.  

PubMed

Human peripheral blood neutrophils were exposed in vitro, in a tonometer, to two different fractions of cigarette smoke-designated particulate phase and vapor phase. The proteolytic activity of the cells following exposure was assessed by measuring their elastase release and ability to degrade fibronectin. At levels of smoke exposure that were physiologically attainable, neither smoke fraction caused an increase in elastase release or fibronectin degradation. In most experiments, fibronectin proteolysis was suppressed by smoke exposure--an effect that was reversible on treatment with phorbol myristate acetate. These data provide evidence that the proteolytic activity of neutrophils is not enhanced by a direct effect of cigarette smoke on these cells. PMID:1959503

Brown, G M; Drost, E; Donaldson, K; MacGregor, I; MacNee, W

1991-01-01

106

Vapor phase VOC transport in physically-mixed clay soils.  

National Technical Information Service (NTIS)

Experiments were conducted to provide insight into the controlling removal mechanisms for a mixed region vapor stripping process in clay soils. Results of soil column experiments were compared to a mathematical model to determine intra-aggregate diffusion...

M. D. Carpenter J. S. Gierke R. L. Siegrist O. R. West

1994-01-01

107

Molecular mechanisms of damage by excess nitrogen oxides: nitration of tyrosine by gas-phase cigarette smoke.  

PubMed

Nitric oxide (nitrogen monoxide, .NO) plays important physiological roles, but an excess can be toxic. .NO is present in cigarette smoke (CS) at up to 500 ppm, and probably represents one of the greatest exogenous sources of .NO to which humans are exposed. We show here that gas-phase CS is capable of converting tyrosine to 3-nitrotyrosine (3-NO2-Tyr) and dityrosine, to an extent dependent on time of exposure and pH. Glutathione, ascorbic acid and uric acid decreased the CS-induced formation of 3-NO2-Tyr and dityrosine. We suggest that nitrogen oxides in CS can modify proteins in the respiratory tract and may contribute to CS toxicity. PMID:7926022

Eiserich, J P; Vossen, V; O'Neill, C A; Halliwell, B; Cross, C E; van der Vliet, A

1994-10-10

108

Analysis of TNT and related compounds in vapor and solid phase in different types of soil  

Microsoft Academic Search

Trinitrotoluene (TNT) explosives contain small amounts of dinitrotoluene (DNT). DNT exhibit a higher vapor pressure than TNT which indicates higher concentration of DNT than of TNT in the vapor phase of the explosive. Analysis of soil samples reveal extended information compared to air samples and thereby increases the probability for chemical detection. Detected substances in soil samples are TNT and

Ann H. Kjellstrom; Lena M. Sarholm

2000-01-01

109

FDA Proposes E-Cigarette Regulations  

MedlinePLUS

... federal oversight. Those products include cigars, pipe tobacco, nicotine gels and waterpipe (or hookah) tobacco. "Today, we' ... E-cigarettes are battery-operated devices that turn nicotine, flavorings and other chemicals into a vapor that ...

110

Evidence of Critical Scaling Behavior During Vapor Phase Synthesis of Continuous Filament Composites.  

National Technical Information Service (NTIS)

The authors present experimental measurements of the accessible pore fraction in ceramic matrix composites during consolidation by vapor phase infiltration. For two topologically distinct filament architectures, the accessible pore fraction decreased duri...

J. H. Kinney D. L. Haupt

1997-01-01

111

Desorption Efficiencies of Vapor Phase Polynuclear Aromatic Compounds on Solid Adsorbents.  

National Technical Information Service (NTIS)

Polynuclear aromatic compounds (PNAs) in the vapor phase can be collected by adsorption onto solid adsorbents. This paper reports the results of a study using several liquid and gas chromatographic packing materials to determine their applicability for va...

K. D. Timmons D. Karlesky E. Johnson I. M. Warner

1984-01-01

112

Vapor Phase Deposition Studies of Phosphate Esters on Metal and Ceramic Surfaces.  

National Technical Information Service (NTIS)

The study focuses on a novel means of lubrication for ceramics and metals at high temperatures; called vapor phase lubrication. The deposition rate and mechanisms of tributyl phosphate ester and tricresyl phosphate ester have been explored. A Thermalgravi...

D. E. Deckman S. M. Hsu E. E. Klaus

1988-01-01

113

Rules governing liquid-vapor equilibria in multicomponent two-phase systems of various natures  

Microsoft Academic Search

The main heterogeneous equilibrium laws in multicomponent two-phase liquid-vapor systems and the main rules governing the behavior of such systems and reported in 2002-2009 are considered from the point of view of modern concepts.

L. A. Serafimov

2010-01-01

114

Vapor-phase hydrogenation in the GLC analysis of sesquiterpene lactones of the eudesmane series  

Microsoft Academic Search

The GLC analysis has been carried out of the products of the vapor-phase hydrogenation of the unsaturated lactoens ofInula helenium L. Tetrahydroalantolactone has been detected for the first time in elecampane rhizones and roots. During the vapor-phase\\u000a hydrogenation of the compounds being analyzed in the presence of a Ni catalyst, a migration of the exocyclic double bond of\\u000a isoalantolactone and

G. G. Rosik; A. G. Kotov; A. A. Beskorovainyi; A. A. Zinchenko; A. A. Reznichenko; N. F. Komissarenko

1991-01-01

115

Different pyrolytic pathways of levoglucosan in vapor- and liquid\\/solid-phases  

Microsoft Academic Search

Influence of the amount of levoglucosan-loading on the pyrolysis behavior was studied in N2 at 400°C with a dual-space closed ampoule reactor. The results indicated that the pyrolytic pathways are different between vapor- and liquid\\/solid-phases. Relative contribution of these two pyrolysis conditions changed depending on the amount of levoglucosan-loading. In vapor-phase, levoglucosan was selectively converted to the non-condensable gas (mainly

Takashi Hosoya; Haruo Kawamoto; Shiro Saka

2008-01-01

116

Vapor-Phase Thermal Conductivity, Vapor Pressure, and Liquid Density of R365mfc  

Microsoft Academic Search

The thermal conductivity of a new fluoroalkane, R365mfc (1,1,1,3,3-pentafluorobutane), important for the production of polyurethane rigid foams, was measured using a transient hot wire method, at temp- eratures between 336.85 K and 377.4 K. The extended corresponding states theory was used successfully to predict the results, with an average absolute deviation of 0.5%. The vapor pressure (302.90 K to 358.15

Isabel M. Marrucho; Nelson S. Oliveira; Ralf Dohrn

2002-01-01

117

The intractable cigarette 'filter problem'  

PubMed Central

Background When lung cancer fears emerged in the 1950s, cigarette companies initiated a shift in cigarette design from unfiltered to filtered cigarettes. Both the ineffectiveness of cigarette filters and the tobacco industry's misleading marketing of the benefits of filtered cigarettes have been well documented. However, during the 1950s and 1960s, American cigarette companies spent millions of dollars to solve what the industry identified as the ‘filter problem’. These extensive filter research and development efforts suggest a phase of genuine optimism among cigarette designers that cigarette filters could be engineered to mitigate the health hazards of smoking. Objective This paper explores the early history of cigarette filter research and development in order to elucidate why and when seemingly sincere filter engineering efforts devolved into manipulations in cigarette design to sustain cigarette marketing and mitigate consumers' concerns about the health consequences of smoking. Methods Relevant word and phrase searches were conducted in the Legacy Tobacco Documents Library online database, Google Patents, and media and medical databases including ProQuest, JSTOR, Medline and PubMed. Results 13 tobacco industry documents were identified that track prominent developments involved in what the industry referred to as the ‘filter problem’. These reveal a period of intense focus on the ‘filter problem’ that persisted from the mid-1950s to the mid-1960s, featuring collaborations between cigarette producers and large American chemical and textile companies to develop effective filters. In addition, the documents reveal how cigarette filter researchers' growing scientific knowledge of smoke chemistry led to increasing recognition that filters were unlikely to offer significant health protection. One of the primary concerns of cigarette producers was to design cigarette filters that could be economically incorporated into the massive scale of cigarette production. The synthetic plastic cellulose acetate became the fundamental cigarette filter material. By the mid-1960s, the meaning of the phrase ‘filter problem’ changed, such that the effort to develop effective filters became a campaign to market cigarette designs that would sustain the myth of cigarette filter efficacy. Conclusions This study indicates that cigarette designers at Philip Morris, British-American Tobacco, Lorillard and other companies believed for a time that they might be able to reduce some of the most dangerous substances in mainstream smoke through advanced engineering of filter tips. In their attempts to accomplish this, they developed the now ubiquitous cellulose acetate cigarette filter. By the mid-1960s cigarette designers realised that the intractability of the ‘filter problem’ derived from a simple fact: that which is harmful in mainstream smoke and that which provides the smoker with ‘satisfaction’ are essentially one and the same. Only in the wake of this realisation did the agenda of cigarette designers appear to transition away from mitigating the health hazards of smoking and towards the perpetuation of the notion that cigarette filters are effective in reducing these hazards. Filters became a marketing tool, designed to keep and recruit smokers as consumers of these hazardous products.

2011-01-01

118

Student Understanding of Liquid-Vapor Phase Equilibrium  

ERIC Educational Resources Information Center

Student understanding of the equilibrium coexistence of a liquid and its vapor was the subject of an extended investigation. Written assessment questions were administered to undergraduates enrolled in introductory physics and chemistry courses. Responses have been analyzed to document conceptual and reasoning difficulties in sufficient detail to…

Boudreaux, Andrew; Campbell, Craig

2012-01-01

119

DETERMINING HOW VAPOR PHASE MTBE REACHES GROUND WATER  

EPA Science Inventory

EPA Region 2 and ORD have funded a RARE project for FY 2005/2006 to evaluate the prospects that MTBE (and other fuel components) in vapors that escape from an underground storage tank (UST) can find its way to ground water produced by monitoring wells at a gasoline filling statio...

120

Vapor Phase Growth of Stannic Oxide Single Crystals.  

National Technical Information Service (NTIS)

Single crystals of stannic oxide, SnO2, of higher purity and with higher Hall mobility than any previously reported have been grown from the vapor using the reaction SnC14 + 2H2 + 02 = SnO2 + 4HCl at 1250C and 10 Torr. The stannic chloride is obtained fro...

C. G. Fanstad A. Linz R. H. Rediker

1969-01-01

121

A Level Set Method for vaporizing two-phase flows  

NASA Astrophysics Data System (ADS)

Development and applications of numerical methods devoted to reactive interface simulations are presented. Emphasis is put on vaporization, where numerical difficulties arise in imposing accurate jump conditions for heat and mass transfers. We use both the Level Set Method and the Ghost Fluid Method to capture the interface motion accurately and to handle suitable jump conditions. A local vaporization mass flow rate per unit of surface area is defined and Stefan flow is involved in the process. Specific care has been devoted to the extension of discontinuous variables across the interface to populate ghost cells, in order to avoid parasitic currents and numerical diffusion across the interface. A projection method is set up to impose both the velocity field continuity and a divergence-free condition for the extended velocity field across the interface. The d2 law is verified in the numerical simulations of the vaporization of an isolated static drop. Results are then presented for a water droplet moving in air. Vapor mass fraction and temperature fields inside and outside the droplet are presented.

Tanguy, Sébastien; Ménard, Thibaut; Berlemont, Alain

2007-02-01

122

Vapor Phase Transport Synthesis of Zeolites from Sol-Gel Precursors  

SciTech Connect

A study of zeolite crystallization from sol-gel precursors using the vapor phase transport synthesis method has been performed. Zeolites (ZSM-5, ZSM-48, Zeolite P, and Sodalite) were crystallized by contacting vapor phase organic or organic-water mixtures with dried sodium silicate and dried sodium alumino-silicate gels. For each precursor gel, a ternary phase system of vapor phase organic reactant molecules was explored. The vapor phase reactant mixtures ranged from pure ethylene diamene, triethylamine, or water, to an equimolar mixture of each. In addition, a series of gels with varied physical and chemical properties were crystallized using the same vapor phase solvent mixture for each gel. The precursor gels and the crystalline products were analyzed via Scanning Electron Microscopy, Electron Dispersive Spectroscopy, X-ray mapping, X-ray powder diffraction, nitrogen surface area, Fourier Transform Infrared Spectroscopy, and thermal analyses. The product phase and purity as a function of the solvent mixture, precursor gel structure, and precursor gel chemistry is discussed.

THOMA,STEVEN G.; NENOFF,TINA M.

2000-07-14

123

E-Cigarettes  

MedlinePLUS

... Health Effects Depression Stress and Smoking Secondhand Smoke LGBT and Smoking Menthol Cigarettes E-Cigarettes Quizzes Free ... Health Effects Depression Stress and Smoking Secondhand Smoke LGBT and Smoking Menthol Cigarettes E-Cigarettes Quizzes Free ...

124

Infrared analysis of vapor phase deposited tricresylphosphate (TCP)  

NASA Technical Reports Server (NTRS)

Infrared transmission was employed to study the formation of a lubricating film deposited on two different substrates at 700 C. The deposit was formed from tricresylphosphate vapors and collected onto a NaCl substrate and on an iron coated NaCl substrate. Analysis of the infrared data suggests that a metal phosphate is formed initially, followed by the formation of organophosphorus polymeric compounds.

Morales, Wilfredo; Hanyaloglu, Bengi; Graham, Earl E.

1994-01-01

125

Chemical Composition of Cigarette Smoke.  

National Technical Information Service (NTIS)

Cigarette smoke is a concentrated aerosol of liquid particles suspended in an atmosphere consisting mainly of nitrogen, oxygen, and carbon dioxide. While the precise chemical composition of the particulate and gaseous phases is dependent on the characteri...

M. R. Guerin

1979-01-01

126

Identification of stable cytotoxic factors in the gas phase extract of cigarette smoke and pharmacological characterization of their cytotoxicity.  

PubMed

Smoking is a major risk factor for atherosclerotic vascular diseases, but the mechanism for its genesis is unknown. We have recently shown that the gas phase of cigarette smoke (nicotine- and tar-free cigarette smoke extract; CSE) likely to reach the systemic circulation contains stable substances which cause cytotoxicity like plasma membrane damage and cell death in cultured cells, and also that the plasma membrane damage is caused through sequential activation of protein kinase C (PKC) and NADPH oxidase (NOX) and the resulting generation of reactive oxygen species (PKC/NOX-dependent mechanism), whereas cell death is caused through PKC/NOX-dependent and -independent mechanisms. To identify these stable substances, the CSE was prepared by passing the main-stream smoke of 10 cigarettes through a Cambridge glass fiber filter, trapping of the smoke in a vessel cooled at -80°C, and subsequent dissolution in 10ml of water. The CSE was fractionated into nine fractions using reversed-phase HPLC, and each fraction was screened for cytotoxicity in cultured cells, using propidium iodide uptake assay for cell membrane damage and MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] reduction assay for cell viability. The cytotoxicity was positive in two of the nine fractions (Fr2 and Fr5). After extraction of the active fractions into dichloromethane, GC/MS analysis identified 2-cyclopenten-1-one (CPO) in Fr5 but none in Fr2. After derivatization of the active fractions with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride, GC/MS analysis identified acrolein, acetone and propionaldehyde in Fr2, and methyl vinyl ketone (MVK) in Fr5. After 4-h incubation, authentic acrolein and MVK induced concentration-dependent cytotoxicity with EC50 values of 75.9±8.2 and 47.0±8.0?M (mean±SEM; n=3), respectively, whereas acetone, propionaldehyde and CPO were without effect. However, after 24-h incubation, CPO induced concentration-dependent cytotoxicity with an EC50 value of 264.0±16.9?M (n=3). The concentrations of acrolein, MVK and CPO in the CSE were 3368±334, 2429±123 and 392.9±31.8?M (n=4), respectively, which were higher than the cytotoxic concentrations. The cytotoxicity of acrolein and MVK consisted of plasma membrane damage and decreased cell viability: the plasma membrane damage was totally prevented by treatment with an inhibitor of PKC or NOX, whereas the decreased cell viability was only partially prevented by these inhibitors. The cytotoxicity of CPO consisted only of decreased cell viability, which was totally resistant to these inhibitors. These results show that acrolein and MVK are responsible for the acute cytotoxicity of the CSE through PKC/NOX-dependent and -independent mechanisms, whereas CPO is responsible for the delayed cytotoxicity of the CSE through a PKC/NOX-independent mechanism. PMID:23981515

Noya, Yoichi; Seki, Koh-Ichi; Asano, Hiroshi; Mai, Yosuke; Horinouchi, Takahiro; Higashi, Tsunehito; Terada, Koji; Hatate, Chizuru; Hoshi, Akimasa; Nepal, Prabha; Horiguchi, Mika; Kuge, Yuji; Miwa, Soichi

2013-12-01

127

Vapor pressures and gas-phase PVT data for 1,1,1,2-tetrafluoroethane  

SciTech Connect

The authors present new data for the vapor pressure and PVT surface of 1,1,1,2-tetrafluoroethane (Refrigerant 134a) in the temperature range 40{degree}C (313 K) to 150{degree}C (423 K). The PVT data are for the gas phase at densities up to one-half critical. Densities of the saturated vapor are derived at five temperatures from the intersections of the experimental isochores with the vapor pressure curve. The data are represented analytically in order to demonstrate experimental precision and to facilitate calculation of thermodynamic properties.

Weber, L.A. (National Institute of Standards and Technology, Gaithersburg, MD (USA))

1989-05-01

128

Synthesis of single phase cubic tin nitride nanoparticles by atmospheric pressure halide vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

In this work tin nitride nanoparticles having controlled size have been synthesized by halide vapor phase epitaxy at atmospheric pressure. Tin nitride nanoparticles having three different sizes: 3 ± 0.5 nm, 6 ± 1.0 nm and 11 ± 1.5 nm have been synthesized simultaneously in a single batch at different substrate temperatures by placing the substrate at different distances from the source. The depositions have been carried out on gold-coated silicon substrates using SnCl 4·5H 2O as the precursor, NH 3 as the nitrogen supplier and N 2 as the carrier gas. This is the first report on the synthesis of tin nitride in nanoparticle form.

Nand, Singh Vidya; Ankur, Khare; Brijesh, Kumar; Raj, Mehta Bodh

2008-05-01

129

Vapor pressures and gas-phase PVT data for 1,1,1,2-tetrafluoroethane  

Microsoft Academic Search

We present new data for the vapor pressure and PVT surface of 1,1,1,2-tetrafluoroethane (Refrigerant 134a) in the temperature range 40° C (313 K) to 150° C (423 K). The PVT data are for the gas phase at densities up to one-half critical. Densities of the saturated vapor are derived at five temperatures from the intersections of the experimental isochores with

L. A. Weber

1989-01-01

130

Development of solid-phase microextraction followed by gas chromatography–mass spectrometry for rapid analysis of volatile organic chemicals in mainstream cigarette smoke  

Microsoft Academic Search

In this work, a novel, simple and efficient method based on solid-phase microextraction (SPME) followed by gas chromatography–mass spectrometry (GC–MS) was developed to the analysis of volatile organic chemicals (VOCs) in mainstream cigarette smoke (MCS). Using a simple home-made smoking machine device, extraction and concentration of VOCs in MCS were performed by SPME fiber, and the VOCs adsorbed on fiber

Qing Ye

2008-01-01

131

Step structure of GaInAsSb grown by OMVPE (Organometallic Vapor Phase Epitaxy)  

SciTech Connect

The microscopic surface morphology of GaInAsSb grown by organometallic vapor phase epitaxy (OMVPE)on GaSb substrates has been studied by atomic force microscopy. The effects of growth temperature, alloy composition, and substrate misorientation on the step structure were investigated. The competition between thermodynamically driven phase separation and kinetically limited surface diffusion is discussed.

Charache, G.W.; Wang, C.A.

1999-05-23

132

Effect of filtration by activated charcoal on the toxicological activity of cigarette mainstream smoke from experimental cigarettes.  

PubMed

Activated charcoal (AC) filtration reportedly decreases the yields of smoke vapor phase constituents including some identified as human carcinogens and respiratory irritants. Non-clinical studies including chemical smoke analysis, in vitro cytotoxicity and mutagenicity (bacterial and mammalian cells), and in vivo subchronic rat inhalation studies were carried out using machine smoking at ISO conditions with lit-end research cigarettes containing AC filters. The objective was to assess whether AC filter technology would alter the established toxicity profile of mainstream smoke by increasing or decreasing any known toxicological properties, or elicit new ones. The reduced yield of vapor phase irritants from AC filter cigarettes correlated with markedly decreased in vitro cytotoxicity and in vivo morphology of the nose and lower respiratory tract. Increased yields of particulate phase constituents (e.g. polycyclic aromatic hydrocarbons) in AC filtered smoke were noted in comparison to controls in some studies. The in vitro bacterial mutagenicity of AC filtered smoke particulate preparations was occasionally increased over control levels. Laryngeal epithelial thickness was increased in some rats inhaling AC filtered smoke in comparison to controls, an effect perhaps related to higher inspiratory flow. When tested under more intense Massachusetts Department of Public Health smoking conditions, AC filter associated reductions in vapor phase constituent yields were smaller than those seen with ISO conditions, but the effect on in vitro cytotoxicity remained. PMID:19555222

Gaworski, Charles L; Schramke, Heike; Diekmann, Joerg; Meisgen, Thomas J; Tewes, Franz J; Veltel, Detlef J; Vanscheeuwijck, Patrick M; Rajendran, Narayanan; Muzzio, Miguel; Haussmann, Hans-Juergen

2009-07-01

133

Vapor-crystal phase transition in synthesis of paracetamol films by vacuum evaporation and condensation  

NASA Astrophysics Data System (ADS)

We report on the structural and technological investigations of the vapor-crystal phase transition during synthesis of paracetamol films of the monoclinic system by vacuum evaporation and condensation in the temperature range 220-320 K. The complex nature of the transformation accompanied by the formation of a gel-like phase is revealed. The results are interpreted using a model according to which the vapor-crystal phase transition is not a simple first-order phase transition, but is a nonlinear superposition of two phase transitions: a first-order transition with a change in density and a second-order phase transition with a change in ordering. Micrographs of the surface of the films are obtained at different phases of formation.

Belyaev, A. P.; Rubets, V. P.; Antipov, V. V.; Bordei, N. S.; Zarembo, V. I.

2014-03-01

134

Determination of pyridine, 2-picoline, 4-picoline and quinoline from mainstream cigarette smoke by solid-phase extraction liquid chromatography/electrospray ionization tandem mass spectrometry.  

PubMed

The present paper describes the development and validation of a new reversed-phase liquid chromatography-electrospray ionization tandem mass spectrometric method (RP-HPLC-ESI-MS/MS) for simultaneous determination of pyridine, 2-picoline, 4-picoline and quinoline from mainstream cigarette smoke. Liquid-liquid extraction followed by solid-phase extraction was applied to extract the target analytes from cigarette smoke. Baseline chromatographic separation was achieved by utilizing a Zorbax SB-Aq (4.6x150 mm, 5 microm) column in gradient chromatographic conditions with acetonitrile and ammonium acetate buffer as mobile phases. Popular commercially available Indian brand filtered and non-filtered cigarettes were analyzed using the same method. The identification of each chemical was established by chromatographic retention times, analyte specific fragmentation patterns and relative peak area ratios of two product/precursor ion pairs. The limit of detection of this method ranged from 1.74 to 14.32 ng/cig using an injection volume of 20 microl. The reproducibility of this method is excellent and better standard deviations were obtained compared to literature reported values for these chemicals. RSD value is less than 9% for all analytes. PMID:20004901

Saha, Subhrakanti; Mistri, Rajib; Ray, B C

2010-01-15

135

Reaction Kinetics of Ethylene Glycol Reforming over Platinum in the Vapor versus Aqueous Phases  

SciTech Connect

First-principles, periodic, density functional theory (DFT) calculations are carried out on Pt(111) to investigate the structure and energetics of dehydrogenated ethylene glycol species and transition states for the cleavage of C-H/O-H and C-C bonds. Additionally, reaction kinetics studies are carried out for the vapor phase reforming of ethylene glycol (C2H6O2) over Pt/Al2O3 at various temperatures, pressures, and feed concentrations. These results are compared to data for aqueous phase reforming of ethylene glycol on this Pt catalyst, as reported in a previous publication (Shabaker, J. W.; et al. J. Catal. 2003, 215, 344). Microkinetic models were developed to describe the reaction kinetics data obtained for both the vapor-phase and aqueous-phase reforming processes. The results suggest that C-C bond scission in ethylene glycol occurs at an intermediate value of x (3 or 4) in C2HxO2. It is also found that similar values of kinetic parameters can be used to describe the vapor and aqueous phase reforming data, suggesting that the vapor phase chemistry of this reaction over platinum is similar to that in the aqueous phase over platinum.

Kandoi, Shampa; Greeley, Jeffrey P.; Simonetti, Dante A.; Shabaker, John; Dumesic, James A.; Mavrikakis, Manos

2010-08-12

136

Reaction kinetics of ethylene glycol reforming over platinum in the vapor versus aqueous phases  

SciTech Connect

First-principles, periodic, density functional theory (DFT) calculations are carried out on Pt(111) to investigate the structure and energetics of dehydrogenated ethylene glycol species and transition states for the cleavage of C-H/O-H and C-C bonds. Additionally, reaction kinetics studies are carried out for the vapor phase reforming of ethylene glycol (C{sub 2}H{sub 6}O{sub 2}) over Pt/Al{sub 2}O{sub 3} at various temperatures, pressures, and feed concentrations. These results are compared to data for aqueous phase reforming of ethylene glycol on this Pt catalyst, as reported in a previous publication (Shabaker, J. W.; et al. J. Catal. 2003, 215, 344). Microkinetic models were developed to describe the reaction kinetics data obtained for both the vapor-phase and aqueous-phase reforming processes. The results suggest that C?C bond scission in ethylene glycol occurs at an intermediate value of x (3 or 4) in C{sub 2}H{sub x}O{sub 2}. It is also found that similar values of kinetic parameters can be used to describe the vapor and aqueous phase reforming data, suggesting that the vapor phase chemistry of this reaction over platinum is similar to that in the aqueous phase over platinum.

Kandoi, S.; Greeley, J.; Simonetti, D.; Shabaker, J.; Dumesic, J. A.; Mavrikakis, M. (Center for Nanoscale Materials); (Univ. of Wisconsin at Madison)

2011-01-01

137

Near-real-time determination of hydrogen peroxide generated from cigarette smoke.  

PubMed

The ability to monitor hydrogen peroxide (H2O2) in aqueous smoke extracts will advance our understanding of the relationship between cigarette smoke-induced oxidative stress, inflammation, and disease and help elucidate the pathways by which the various smoke constituents exert their pathogenic effects. We have demonstrated, for the first time, the measurement of H2O2 production from cigarette smoke without prior separation of the sample. Cigarettes were tested on a commercial smoking machine, such that the whole smoke or gas vapor phase was bubbled through phosphate buffered saline solution at pH 7.4. Aliquots of these solutions were analyzed using an Amplex Red/horseradish peroxidase fluorimetric assay that required only a 2 minute incubation time, facilitating the rapid, facile collection of data. Catalase was used to demonstrate the selectivity and specificity of the assay for H2O2 in the complex smoke matrix. We measured approximately 7-8 microM H2O2 from two reference cigarettes (i.e., 1R4F and 2R4F). We also observed 9x more H2O2 from whole smoke bubbled samples compared to the gas vapor phase, indicating that the major constituent(s) responsible for H2O2 formation reside in the particulate phase of cigarette smoke. Aqueous solutions of hydroquinone and catechol, both of which are particulate phase constituents of cigarette smoke, generated no H2O2 even though they are free radical precursors involved in the production of reactive oxygen species in the smoke matrix. PMID:15986047

Yan, Fei; Williams, Serene; Griffin, Guy D; Jagannathan, Ramesh; Plunkett, Susan E; Shafer, Kenneth H; Vo-Dinh, Tuan

2005-07-01

138

Se vapor pressure dependence of the phase diagram of the CuGa 1? x In x Se 2 system  

Microsoft Academic Search

Phase transition points of the CuGa1?xInxSe2 system are investigated by the differential thermal analysis with varying Se vapor pressure up to 760Torr. The phase diagrams constructed under controlled Se vapor pressure show that the solidus and liquidus points decrease more than 100°C with increasing Se vapor pressure, and that the temperature zone of the (sphalerite+liquid) phase narrows in the region

Hiroaki Matsushita; Takeo Takizawa

1998-01-01

139

Liquid-vapor phase separation in a thermocapillary force field  

NASA Astrophysics Data System (ADS)

We study the growth of gas bubbles surrounded by liquid during the phase separation of a pure CO2 sample quenched from one-phase to two-phase region of the phase diagram by rapid cooling in microgravity. The vicinity of the critical point ensures slowing-down of the growth process. The bubble growth by coalescence is modified by local laser heating. It induces a thermocapillary (Marangoni) effect that attracts the bubbles towards the center of the beam. At the beginning of the phase separation, a bubble is trapped there and "captures" the surrounding bubbles. The growth exponent for the central bubble radius is close to 0.5, while that for the other bubbles is 1/3. We present a theoretical model that explains the experimental data and justifies that the temperature can vary along the gas-liquid interface in a pure fluid during its phase separation.

Beysens, D.; Garrabos, Y.; Nikolayev, V. S.; Lecoutre-Chabot, C.; Delville, J.-P.; Hegseth, J.

2002-07-01

140

A Preliminary Study on the Vapor/Mist Phase Lubrication of a Spur Gearbox  

NASA Technical Reports Server (NTRS)

Organophosphates have been the primary compounds used in vapor/mist phase lubrication studies involving ferrous bearing material. Experimental results have indicated that the initial formation of an iron phosphate film on a rubbing ferrous surface, followed by the growth (by cationic diffusion) of a lubricious pyrophosphate-type coating over the iron phosphate, is the reason organophosphates work well as vapor/mist phase lubricants. Recent work, however, has shown that this mechanism leads to the depletion of surface iron atoms and to eventual lubrication failure. A new organophosphate formulation was developed which circumvents surface iron depletion. This formulation was tested by generating an iron phosphate coating on an aluminum surface. The new formulation was then used to vapor/mist phase lubricate a spur gearbox in a preliminary study.

Morales, Wilfredo; Handschuh, Robert F.

1999-01-01

141

Chemical Vapor Identification Using Field-Based Attenuated Total Reflectance Fourier Transform Infrared Detection and Solid Phase Microextraction.  

National Technical Information Service (NTIS)

Attenuated total reflectance Fourier transform infrared (ATR-FTIR) technology is used to identify chemicals in a liquid or solid phase but not in a vapor phase. This research identified vapor phase chemicals using a field- portable ATR-FTIR spectrometer c...

C. K. Bryant

2004-01-01

142

MEMS Lubrication by In-Situ Tribochemical Reactions From the Vapor Phase.  

SciTech Connect

Vapor Phase Lubrication (VPL) of silicon surfaces with pentanol has been demonstrated. Two potential show stoppers with respect to application of this approach to real MEMS devices have been investigated. Water vapor was found to reduce the effectiveness of VPL with alcohol for a given alcohol concentration, but the basic reaction mechanism observed in water-free environments is still active, and devices operated much longer in mixed alcohol and water vapor environments than with chemisorbed monolayer lubricants alone. Complex MEMS gear trains were successfully lubricated with alcohol vapors, resulting in a factor of 104 improvement in operating life without failure. Complex devices could be made to fail if operated at much higher frequencies than previously used, and there is some evidence that the observed failure is due to accumulation of reaction products at deeply buried interfaces. However, if hypothetical reaction mechanisms involving heated surfaces are valid, then the failures observed at high frequency may not be relevant to operation at normal frequencies. Therefore, this work demonstrates that VPL is a viable approach for complex MEMS devices in conventional packages. Further study of the VPL reaction mechanisms are recommended so that the vapor composition may be optimized for low friction and for different substrate materials with potential application to conventionally fabricated, metal alloy parts in weapons systems. Reaction kinetics should be studied to define effective lubrication regimes as a function of the partial pressure of the vapor phase constituent, interfacial shear rate, substrate composition, and temperature.

Dugger, Michael T.; Asay, David B.; Kim, Seong H.

2008-01-01

143

Effect of vapor phase corrosion inhibitor on microbial corrosion of aluminum alloys.  

PubMed

Vapor phase corrosion inhibitors were used to investigate the antimicrobial activities and anticorrosion of aluminum alloy. Aspergillus flavus, A. niger, A. versicolor, Chaetomium globosum and Penicillium funiculosum had moderate to abundant growth on the aluminum alloy AA 1100 at Aw 0.901, while there was less growth at Aw 0.842. High humidity stimulated microbial growth and induced microbial corrosion. Dicyclohexylammonium carbonate had a high inhibitory effect on the growth of test fungi and the microbial corrosion of aluminum alloy, dicyclohexylammonium caprate and dicyclohexylammonium stearate were the next. Aluminum alloy coating with vapor phase corrosion inhibitor could prevent microbial growth and retard microbial corrosion. PMID:10592784

Yang, S S; Ku, C H; Bor, H J; Lin, Y T

1996-02-01

144

Measurements of the thermal conductivity of refrigerants in the vapor phase  

SciTech Connect

Measurements of the thermal conductivity of refrigerants R124, R125, and R134a in the vapor phase are presented. The measurements, performed in a newly developed transient hot-wire instrument, cover a temperature range from 273 to 333 K, and a pressure range from about atmospheric up to below the saturation pressure. A finite-elements program developed allowed the reexamination of the major corrections employed in the analysis of the results. The uncertainty of the reported values is estimated to be better than {+-}1%. Comparisons with measurements of other investigators along the saturation line show a lack of reliable thermal conductivity data in the vapor phase for these compounds.

Assael, M.J.; Malamataris, N.; Karagiannidis, L. [Aristotle Univ., Thessaloniki (Greece). Faculty of Chemical Engineering

1997-03-01

145

Fluid dynamics and thermodynamics of vapor phase crystal growth  

NASA Technical Reports Server (NTRS)

The ground-based research effort under this program is concerned with systematic studies of the effects of variations: (1) of the relative importance of buoyancy-driven convection, and (2) of diffusion and viscosity conditions on crystal properties. These experimental studies are supported by thermodynamic characterizations of the systems, based on which fluid dynamic parameters can be determined. The specific materials under investigation include: the GeSe-GeI4, Ge-GeI4, HgTe-HgI2, and Hg sub (1-x)Cd sub (x) Te-HgI2 systems. Mass transport rate studies of the GeSe-GeI system as a function of orientation of the density gradient relative to the gravity vector demonstrated the validity of flux anomalies observed in earlier space experiments. The investigation of the effects of inert gases on mass flux yielded the first experimental evidence for the existence of a boundary layer in closed ampoules. Combined with a thorough thermodynamic analysis, a transport model for diffusive flow including chemical vapor transport, sublimation, and Stefan flow was developed.

Wiedemeier, H.

1985-01-01

146

Properties of polyimide shells made using vapor phase deposition  

SciTech Connect

Hollow polyimide shells, to be used in inertial confinement fusion experiments, were fabricated by codepositing monomer precursors onto spherical mandrels. Polyimide shells with 700 to 950 {mu}m diameters and 4 to 13 {mu}m wall thicknesses were produced. The shell wall shrunk 20{endash}30{percent} due to imidization. Burst and buckle pressure tests on these shells yielded estimated mechanical strength properties: {approximately}15 GPa elastic modulus and {approximately}300 MPa tensile strength. The permeability of D{sub 2} through polyamic acid at 298 K was 7.4{times}10{sup {minus}17}thinspmol{center_dot}m/m{sup 2}{center_dot}Pa{center_dot}s and increased to 6.4{times}10{sup {minus}16}thinspmol{center_dot}m/m{sup 2}{center_dot}Pa{center_dot}s upon curing the shell to 150thinsp{degree}C. The permeability of D{sub 2} at 298 K through vapor-deposited polyimide flat films was 240 times greater than through polyamic acid. {copyright} {ital 1998 Materials Research Society.}

Alfonso, E.L.; Chen, S.H.; Gram, R.Q.; Harding, D.R. [Laboratory For Laser Energetics, University of Rochester, Rochester, New York 14623-1299 (United States)

1998-10-01

147

Condensed phase conversion and growth of nanorods and other materials instead of from vapor  

DOEpatents

Compositions, systems and methods are described for condensed phase conversion and growth of nanorods and other materials. A method includes providing a condensed phase matrix material; and activating the condensed phase matrix material to produce a plurality of nanorods by condensed phase conversion and growth from the condensed phase matrix material instead of from vapor. The compositions are very strong. The compositions and methods provide advantages because they allow (1) formation rates of nanostructures necessary for reasonable production rates, and (2) the near net shaped production of component structures.

Geohegan, David B. (Knoxville, TN); Seals, Roland D. (Oak Ridge, TN); Puretzky, Alex A. (Knoxville, TN); Fan, Xudong (Oak Ridge, TN)

2010-10-19

148

Gallium hydride vapor phase epitaxy of GaN nanowires  

PubMed Central

Straight GaN nanowires (NWs) with diameters of 50 nm, lengths up to 10 ?m and a hexagonal wurtzite crystal structure have been grown at 900°C on 0.5 nm Au/Si(001) via the reaction of Ga with NH3 and N2:H2, where the H2 content was varied between 10 and 100%. The growth of high-quality GaN NWs depends critically on the thickness of Au and Ga vapor pressure while no deposition occurs on plain Si(001). Increasing the H2 content leads to an increase in the growth rate, a reduction in the areal density of the GaN NWs and a suppression of the underlying amorphous (?)-like GaN layer which occurs without H2. The increase in growth rate with H2 content is a direct consequence of the reaction of Ga with H2 which leads to the formation of Ga hydride that reacts efficiently with NH3 at the top of the GaN NWs. Moreover, the reduction in the areal density of the GaN NWs and suppression of the ?-like GaN layer is attributed to the reaction of H2 with Ga in the immediate vicinity of the Au NPs. Finally, the incorporation of H2 leads to a significant improvement in the near band edge photoluminescence through a suppression of the non-radiative recombination via surface states which become passivated not only via H2, but also via a reduction of O2-related defects.

2011-01-01

149

Solid and Vapor Phase UV Photocathodes for Gaseous Detectors  

SciTech Connect

We measured the relative quantum efficiency of four organic materials: tetrathiafulvalene and bis(cyclopentadienyl)magnesium in the solidphase and t-butylferrocene and n-butylferrocene in the vapour phase. The measurements were performed in the wavelength range of 150-220 nm. We also present a new quantum efficiency measurement of ethylferrocene. The three ferrocene derivatives exhibit relatively high quantum efficiency.

Vasileiadis, G.; Malamud, G.; Mine, P.; Vartsky, D.; /Ecole Polytechnique

2012-09-20

150

Heterodyne phase shift diagnostic for measuring atomic vapor density  

SciTech Connect

We describe a technique for atomic density measurements. We generate and recombine frequency shifted laser beams producing beat signals on reference and signal detectors. Opacity in the signal detector leg is proportional to the phase difference between detector signals. 4 refs., 2 figs.

Crane, J.K.; Paisner, J.A.; Johnson, M.A.; Story, T.W.; Barclay, C.; George, J.D.; Wyeth, R.W.; Christensen, J.J.

1987-11-12

151

Development of solid-phase microextraction followed by gas chromatography-mass spectrometry for rapid analysis of volatile organic chemicals in mainstream cigarette smoke.  

PubMed

In this work, a novel, simple and efficient method based on solid-phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) was developed to the analysis of volatile organic chemicals (VOCs) in mainstream cigarette smoke (MCS). Using a simple home-made smoking machine device, extraction and concentration of VOCs in MCS were performed by SPME fiber, and the VOCs adsorbed on fiber were desorbed, and analyzed by GC-MS. The extraction fiber types and the desorption conditions were studied, and the method precision was also investigated. After the investigation, the optimal fiber was divinylbenzene/carboxen/polydemethylsiloxane (DVB/CAR/PDMS), and the optimal desorption condition was 250 degrees C for 3 min. The method precision was from 2% to 11%. Finally, the proposed method was tested by its application of the analysis of VOCs in MCS from 10 brands of cigarettes and one reference cigarette. A total of 70 volatile compounds were identified by the proposed method. The experimental results showed that the proposed method was a simple, rapid, reliable, and solvent-free technique for the determination of VOCs in MCS. PMID:18992893

Ye, Qing

2008-12-12

152

The control of gas phase kinetics to maximize densification during chemical vapor infiltration  

Microsoft Academic Search

A serious problem during the fabrication of composite materials by isothermal chemical vapor infiltration is that the matrix forms more rapidly at the external edges of the body and traps a large amount of porosity inside. In theory, this problem can be eliminated by controlling the gas-phase kinetics to obtain densification which is more rapid in the center of a

Brian W. Sheldon

1990-01-01

153

ORGANIC CHARACTERIZATION OF AEROSOLS AND VAPOR PHASE COMPOUNDS IN URBAN ATMOSPHERES  

EPA Science Inventory

Organic pollutants in urban atmospheres were characterized by analyzing particulate and/or vapor-phase samples collected by EPA in St. Louis, Missouri; Miami, Florida; Denver, Colorado; Houston, Texas; and at the General Motors Test Track in Milford, Michigan. The particulate sam...

154

Quantitative Vapor-Phase FTIR Spectra of Dimethyl Methylphosphonate and Methyl Salicylate.  

National Technical Information Service (NTIS)

This report summarizes the results of initial tests under Contract No. DAAM01-97-D-0015, Task Order No. 0022. The scope of work was to provide preliminary validation of a system for generating quantitative vapor-phase Fourier transform infrared spectra of...

B. R. Williams D. E. Tevault L. C. Buettner

2001-01-01

155

Vapor-Phase Absorptivity Coefficient of Ethyl N,N- Dimethylphosphoramidocyanidate.  

National Technical Information Service (NTIS)

We measured the vapor-phase absorptivity coefficient of the chemical warfare agent ethyl N,N-dimethylphosphoramidocyanidate (GA) in the mid-infrared (4000-550 cm'') at a spectral resolution of 0.125 cm''. The GA used in the feedstock was purified by fract...

A. C. Samuels B. R. William J. R. Miles M. S. Hulet

2010-01-01

156

Triple sorbent thermal desorption/gas chromatography/mass spectrometry determination of vapor phase organic contaminants.  

National Technical Information Service (NTIS)

A thermal desorption/ps chromatography/mass spectrometry (TD/GC/MS) has been evaluated for the determination of volatile organic compounds (VOCS) in vapor phase samples using Carbosieve S-III/Carbotrap/Carotrap C triple sorbent traps (TST) similar to thos...

C. Y. Ma J. T. Skeen A. B. Dindal C. E. Higgins R. A. Jenkins

1994-01-01

157

A technique for eliminating white phosphorus deposits in vapor phase epitaxy systems  

NASA Technical Reports Server (NTRS)

A technique of heating the exhaust lines is described whereby phosphorus in the exhaust portion of an organometallic vapor phase epitaxy reactor is encouraged to deposit in the red form rather than the pyrophoric white form. This technique is simple, effective, and does not hinder or limit the conditions under which the reactor may be operated.

Wilt, D. M.; Hoffman, R. W.

1993-01-01

158

Rules governing liquid-vapor equilibria in multicomponent two-phase systems of various natures  

Microsoft Academic Search

The main heterogeneous equilibrium laws in multicomponent two-phase liquid-vapor systems and the main rules governing the\\u000a behavior of such systems and reported in 2002–2009 are considered from the point of view of modern concepts.

L. A. Serafimov

2010-01-01

159

Vapor phase growth of group 3, 4, and 5 compounds by HCl transport of elements  

NASA Technical Reports Server (NTRS)

Technique has been devised for vapor-phase epitaxial growth of group 3, 4, and 5 binary, ternary, or quaternary compounds by HCl transport of the constituent elements or dopants. Technique uses all the constituents of the alloy system in their elemental form. Transport of these elements by an HCl + H2 carrier gas facilitates their transport as subchlorides.

Tyagi, R. C.; Debnam, W. J., Jr.; Mcnear, M. F.; Crouch, R. K.; Breckenridge, R. A.

1973-01-01

160

EFFECT OF VAPOR-PHASE BIOREACTOR OPERATION ON BIOMASS ACCUMULATION, DISTRIBUTION, AND ACTIVITY. (R826168)  

EPA Science Inventory

Excess biomass accumulation and activity loss in vapor-phase bioreactors (VPBs) can lead to unreliable long-term operation. In this study, temporal and spatial variations in biomass accumulation, distribution and activity in VPBs treating toluene-contaminated air were monitored o...

161

VAPOR PHASE MERCURY SORPTION BY ORGANIC-SULFIDE COATED BIMETALLIC IRON-COPPER NANOPARTICLE AGGREGATES  

EPA Science Inventory

Tetra sulfide silane coated iron-copper nano-particle aggregates are found to be potentially very high capacity sorbents for vapor phase mercury capture. High equilibrium capacities were obtained for the silane coated iron copper nano-aggregate sorbent at 70 oC and 120 oC. Even a...

162

Complete Compensation of Self-Phase Modulation in Cesium Vapor at 1.06 Microns.  

National Technical Information Service (NTIS)

The authors have observed a complete cancellation of self-phase modulation at 1.06 micrometers pulses propagating through cesium vapor. The negative nonlinear refractive index responsible for this is measured as n2/N=-(2.5 + or - .5) x 10 to the -30th pow...

R. H. Lehmberg J. Reintjes R. C. Eckardt

1977-01-01

163

The effect of triplet quenchers on vapor-phase dye-laser performance  

NASA Astrophysics Data System (ADS)

An XeF pumped vapor phase POPOP dye laser with a pulse duration of 300 ns was obtained when trans-stilbene was used as triplet quencher. An energy conversion efficiency of 7,5% with a peak power efficiency of 12% was measured.

Klimek, D. E.

1984-06-01

164

Zno/cu(inga)se2 Solar Cells Prepared by Vapor Phase zn Doping.  

National Technical Information Service (NTIS)

A process for making a thin film ZnO/Cu(InGa)Se.sub.2 solar cell without depositing a buffer layer and by Zn doping from a vapor phase, comprising: depositing Cu(InGa)Se.sub.2 layer on a metal back contact deposited on a glass substrate; heating the Cu(In...

F. S. Hasoon J. Dolan J. C. Keane K. Ramanathan S. E. Asher

2003-01-01

165

Selected Vapor Phase Sensing of Small Molecules Using Biofunctionalized Field Effect Transistors.  

National Technical Information Service (NTIS)

This work details a proof of concept study for vapor phase selective sensing using a strategy of biorecognition elements (BRE) integrated into a zinc oxide field effect transistor (ZnO FET). ZnO FETs are highly sensitive to changes to the environment with...

J. A. Hagen M. O. Stone N. Kelley-Loughnane R. R. Naik S. N. Kim

2012-01-01

166

Vapor-phase deposition studies of phosphate esters on metal and ceramic surfaces. Final report  

SciTech Connect

This study focuses on a novel means of lubrication for ceramics and metals at high temperatures; called vapor-phase lubrication. The deposition rate and mechanisms of tributyl phosphate ester and tricresyl phosphate ester were explored. A thermalgravimetric analyzer (TGA) was modified to measure the rate of surface-film formation of vapor phase deposition of lubricants on metal surfaces at elevated temperatures. Results from TGA studies showed that the vapor-deposition process was a complex function of substrate, time, and temperature. Tricresyl phosphate ester (TCP) and tributyl ester (TBP) were observed to produce similar amounts of film on stainless steel substrates. The observed order of metal activity was copper > stainless steel > nickel > platinum. Film formation on nickel was found to be much more rapid at 600 C than 700 C. Also, the concentration of oxygen present during deposition strongly influenced the amount of film formed. Scanning electron microscopy was conducted on TBP films formed on Si/sub 3/N/sub 4/, Al/sub 2/O/sub 3/, and alpha-SiC. The films produced contained globule and filamentous structures. The films on each ceramic were unique, demonstrating that vapor deposition is surface-sensitive on ceramic substrates. High-temperature friction testing was conducted on a TCP coated Al/sub 2/O/sub 3/ substrate. The coating reduced the friction level for alumina, thus demonstrating the potential of vapor lubrication for high-temperature lubrication of ceramics.

Deckman, D.E.; Hsu, S.M.; Klaus, E.E.

1988-09-01

167

Simultaneous chemical vapor deposition of SiC-dispersed phase composites  

SciTech Connect

Ceramic composites are being developed because they can have high strength and toughness yet retain the normal ceramic attributes of refractoriness and high resistance to abrasion and corrosion. In the present research, toughened ceramic composites were produced by the simultaneous chemical vapor deposition of an SiC matrix and a dispersed phase of TiSi/sub 2/. The morphology of the dispersed phase was found to control the mechanical properties of the composite. Deposition of coatings in a fluidized bed produced a finer and more uniformly dispersed second phase. The conditions within the fluidized bed such as temperature, gas composition, and hydrogen flow also affected the morphology of the TiSi/sub 2/ phase. The fracture toughness values for these composite coatings approached 5.5 MPa..sqrt..m at 25/sup 0/C, which is significantly higher than the toughness value for chemically vapor deposited SiC.

Stinton, D.P.; Lackey, W.J.

1985-01-01

168

Vapor-condensed phase processes in the early solar system  

Microsoft Academic Search

Equilibrium thermodynamic calculations of the sequence of condensation of phases from a cooling gas of solar composition at total pressures thought to have prevailed in the inner part of the solar nebula successfully predict the primary mineral assemblages of refractory inclusions in CM2 and CV3 chondrites. Many refractory inclusions in CM2 chondrites contain a relatively SiO2-poor assemblage (spinel, hibonite, grossite,

Lawrence Grossman

2010-01-01

169

Waste retrieval sluicing system vapor sampling and analysis plan for evaluation of organic emissions, process test phase III  

Microsoft Academic Search

This sampling and analysis plan identifies characterization objectives pertaining to sample collection, laboratory analytical evaluation, and reporting requirements for vapor samples obtained to address vapor issues related to the sluicing of tank 241-C-106. Sampling will be performed in accordance with Waste Retrieval Sluicing System Emissions Collection Phase III (Jones 1999) and Process Test Plan Phase III, Waste Retrieval Sluicing System

1999-01-01

170

Analysis of gas phase compounds in chemical vapor deposition of carbon from light hydrocarbons  

Microsoft Academic Search

Product distributions in the pyrolysis of ethylene, acetylene, and propylene are studied to obtain an experimental database for a detailed kinetic modeling of gas phase reactions in chemical vapor deposition of carbon from these light hydrocarbons. Experiments were performed with a vertical flow reactor at 900°C and pressures from 2 to 15kPa. Gas phase components were analyzed by both on-line

Koyo Norinaga; Olaf Deutschmann; Klaus J. Hüttinger

2006-01-01

171

Transmission Electron Microscopy Characterization of Semiconductors Grown by Organometallic Vapor Phase Epitaxy  

Microsoft Academic Search

Microstructural analysis by transmission electron microscopy has been investigated in this dissertation. Phenomena such as spinodal decomposition and ordering in III\\/V alloys grown by organometallic vapor phase epitaxy have been the particular topics. No direct evidence of spinodal decomposition was observed in high quality as-grown GaAs_ {0.5}Sb_{0.5} alloys. After annealing, phase separation occurred at the epilayer surface. However, this phenomenon

Hei-Ruey Harry Jen

1989-01-01

172

Vapor–liquid phase behavior of binary systems of hydrogen chloride and certain n-alkanes  

Microsoft Academic Search

This contribution reports on experimental data of the vapor–liquid phase behavior of the binary system hydrogen chloride+ethane. It was confirmed that the system hydrogen chloride+ethane has type-I fluid phase behavior in the classification of Van Konynenburg and Scott with maximum pressure azeotropy. As an additional feature, it turned out that no reaction between hydrogen chloride and the mercury present in

L. J Florusse; C. J Peters

2002-01-01

173

Plasma Spray-PVD: A New Thermal Spray Process to Deposit Out of the Vapor Phase  

NASA Astrophysics Data System (ADS)

Plasma spray-physical vapor deposition (PS-PVD) is a low pressure plasma spray technology recently developed by Sulzer Metco AG (Switzerland). Even though it is a thermal spray process, it can deposit coatings out of the vapor phase. The basis of PS-PVD is the low pressure plasma spraying (LPPS) technology that has been well established in industry for several years. In comparison to conventional vacuum plasma spraying (VPS) or low pressure plasma spraying (LPPS), the new proposed process uses a high energy plasma gun operated at a reduced work pressure of 0.1 kPa (1 mbar). Owing to the high energy plasma and further reduced work pressure, PS-PVD is able to deposit a coating not only by melting the feed stock material which builds up a layer from liquid splats but also by vaporizing the injected material. Therefore, the PS-PVD process fills the gap between the conventional physical vapor deposition (PVD) technologies and standard thermal spray processes. The possibility to vaporize feedstock material and to produce layers out of the vapor phase results in new and unique coating microstructures. The properties of such coatings are superior to those of thermal spray and electron beam-physical vapor deposition (EB-PVD) coatings. In contrast to EB-PVD, PS-PVD incorporates the vaporized coating material into a supersonic plasma plume. Owing to the forced gas stream of the plasma jet, complex shaped parts such as multi-airfoil turbine vanes can be coated with columnar thermal barrier coatings using PS-PVD. Even shadowed areas and areas which are not in the line of sight of the coating source can be coated homogeneously. This article reports on the progress made by Sulzer Metco in developing a thermal spray process to produce coatings out of the vapor phase. Columnar thermal barrier coatings made of Yttria-stabilized Zircona (YSZ) are optimized to serve in a turbine engine. This process includes not only preferable coating properties such as strain tolerance and erosion resistance but also the simultaneous coverage of multiple air foils.

von Niessen, Konstantin; Gindrat, Malko

2011-06-01

174

Higher cigarette prices influence cigarette purchase patterns  

PubMed Central

Objective: To examine cigarette purchasing patterns of current smokers and to determine the effects of cigarette price on use of cheaper sources, discount/generic cigarettes, and coupons. Background: Higher cigarette prices result in decreased cigarette consumption, but price sensitive smokers may seek lower priced or tax-free cigarette sources, especially if they are readily available. This price avoidance behaviour costs states excise tax money and dampens the health impact of higher cigarette prices. Methods: Telephone survey data from 3602 US smokers who were originally in the COMMIT (community intervention trial for smoking cessation) study were analysed to assess cigarette purchase patterns, use of discount/generic cigarettes, and use of coupons. Results: 59% reported engaging in a high price avoidance strategy, including 34% who regularly purchase from a low or untaxed venue, 28% who smoke a discount/generic cigarette brand, and 18% who report using cigarette coupons more frequently that they did five years ago. The report of engaging in a price avoidance strategy was associated with living within 40 miles of a state or Indian reservation with lower cigarette excise taxes, higher average cigarette consumption, white, non-Hispanic race/ethnicity, and female sex. Conclusion: Data from this study indicate that most smokers are price sensitive and seek out measures to purchase less expensive cigarettes, which may decrease future cessation efforts.

Hyland, A; Bauer, J; Li, Q; Abrams, S; Higbee, C; Peppone, L; Cummings, K

2005-01-01

175

Synthesis of aligned ZnO nanocolumn arrays by a vapor phase transport method  

NASA Astrophysics Data System (ADS)

Vertically large-scale aligned ZnO nanocolumn arrays have been synthesized on Si(100) substrate at 550°C via a simple vapor phase transport process in a horizontal chemical vapor depositon (CVD) reactor. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show that the ZnO nanocolumns have a uniform length of about 3 ?m with an average diameter of 80 nm. The clear lattice fringes in HRTEM image indicate the synthesis of good quality hexagonal single crystal ZnO. The X-ray diffraction (XRD) result shows the nanocolumns are c-axis preferentially oriented.

Li, Gang

2012-12-01

176

The case of the electronic cigarette in the EU.  

PubMed

Although the electronic cigarette was invented in 2004, only recently the product has started to provoke discussion. On the one hand, the electronic cigarette is characterized by scientific uncertainties. It is not clear whether the device can be used in smoking cessation therapy, whether the use induces non-smokers--including minors--to start smoking and whether the vaporized substances and the act of vaporizing itself (which is smoking an electronic cigarette) is harmful. On the other hand, there is no harmonised European legal framework and different Member States attribute a different legal status to the e-cigarette. In this article, the author analyses how the e-cigarette should be qualified according to the current European legislation and ECJ case law and describes how the e-cigarette is qualified in the UK, France, The Netherlands, Belgium and Spain. PMID:24851651

Syx, Eugenie

2014-04-01

177

Phase-transition thresholds and vaporization phenomena for ultrasound phase-change nanoemulsions assessed via high-speed optical microscopy  

NASA Astrophysics Data System (ADS)

Ultrasonically activated phase-change contrast agents (PCCAs) based on perfluorocarbon droplets have been proposed for a variety of therapeutic and diagnostic clinical applications. When generated at the nanoscale, droplets may be small enough to exit the vascular space and then be induced to vaporize with high spatial and temporal specificity by externally-applied ultrasound. The use of acoustical techniques for optimizing ultrasound parameters for given applications can be a significant challenge for nanoscale PCCAs due to the contributions of larger outlier droplets. Similarly, optical techniques can be a challenge due to the sub-micron size of nanodroplet agents and resolution limits of optical microscopy. In this study, an optical method for determining activation thresholds of nanoscale emulsions based on the in vitro distribution of bubbles resulting from vaporization of PCCAs after single, short (<10 cycles) ultrasound pulses is evaluated. Through ultra-high-speed microscopy it is shown that the bubbles produced early in the pulse from vaporized droplets are strongly affected by subsequent cycles of the vaporization pulse, and these effects increase with pulse length. Results show that decafluorobutane nanoemulsions with peak diameters on the order of 200 nm can be optimally vaporized with short pulses using pressures amenable to clinical diagnostic ultrasound machines.

Sheeran, Paul S.; Matsunaga, Terry O.; Dayton, Paul A.

2013-07-01

178

Liquid-phase and vapor-phase dehydration of organic/water solutions  

DOEpatents

Processes for dehydrating an organic/water solution by pervaporation or vapor separation using fluorinated membranes. The processes are particularly useful for treating mixtures containing light organic components, such as ethanol, isopropanol or acetic acid.

Huang, Yu (Palo Alto, CA); Ly, Jennifer (San Jose, CA); Aldajani, Tiem (San Jose, CA); Baker, Richard W. (Palo Alto, CA)

2011-08-23

179

An intercomparison of measurement systems for vapor and particulate phase concentrations of formic and acetic acids  

NASA Technical Reports Server (NTRS)

During June 1986, eight systems for measuring vapor phase and four for measuring particulate phase concentrations of formic acid (HCOOH) and acetic acid (CH3COOH) were intercompared in central Virginia. HCOOH and CH3COOH vapors were sampled by condensate, mist, Chromosorb 103 GC resin, NaOH-coated annular denuders, NaOH-impregnated quartz filters, K2CO3 and NaCO3-impregnated cellulose filters, and Nylasorb membranes. Atmospheric aerosol was collected on Teflon and Nuclepore filters using both hi-vol and lo-vol systems to measure particulate phase concentrations. Performances of the mist chamber and K2CO3-impregnated filter techniques were evaluated using zero air and ambient air spiked with HCOOH(g) and CH3COOH(g), and formaldehyde from permeation sources. The advantages and drawbacks of these methods are reported and discussed.

Keene, William C.; Talbot, Robert W.; Andreae, Meinrat O.; Beecher, Kristene; Berresheim, Harold

1989-01-01

180

Photoluminescence of nanoparticles in vapor phase of colliding plasma  

NASA Astrophysics Data System (ADS)

We report photoluminescence observed from ZnO nano particles/clusters formed in gaseous phase of two colliding plumes ZnO plasma using fourth harmonic 266 nm of Nd:YAG laser. The two expanding plumes generated using 1.06 ?m of Nd:YAG laser interact with each other, resulting in an overlap region where the collision front in lateral direction of two plumes forms an overlapping region starting at ~20 ns lasting ~5 ?s with respect to ablating pulse. The blue shift in peak position (~30-5 meV) of photoluminescence profile of ZnO clusters to that observed in bulk ZnO shows the effect of quantum confinement. The dynamical growth of nanoparticles is ascertained using Rayleigh scattered second harmonic radiation at 532 nm of Nd:YAG laser. A combined photoluminescence and light scattering at longer time delays ~1.5 ms where plasma emission is absent confirms the formation of the nano-particles/clusters of ZnO. Observed intensity variation in the Rayleigh scattered signal and blue shift in photoluminescence peak position at different temporal delays with respect to the ablation pulse corroborates the presence and size variation of nano-particles/clusters. The defect related emission band arising due to oxygen vacancy is not observed from the ZnO clusters.

Gupta, Shyam L.; Thareja, Raj K.

2013-04-01

181

Molecular dynamics simulation of liquid-vapor phase equilibria in polar fluids  

NASA Astrophysics Data System (ADS)

A new molecular dynamics simulation technique in the grand canonical ensemble [H. Eslami, F. Müller-Plathe, J. Comput. Chem. 28 (2007) 1763], has been employed to calculate the chemical potentials in the coexisting liquid and vapor phases of pure water, methanol, and acetonitrile. Calculating the chemical potentials in the liquid phase, a new method [J. Vrabec, H. Hasse, Mol. Phys. 100 (2002) 3375], has been employed to calculate the phase coexistence point. In this method just two independent simulations in the grand canonical ensemble are needed to be performed and the molecules are inserted into or deleted from the system in a dynamical way.

Eslami, Hossein; Dargahi, Ali; Behnejad, Hassan

2009-04-01

182

VUV photoionization of gas phase adenine and cytosine: A comparison between oven and aerosol vaporization  

NASA Astrophysics Data System (ADS)

We studied the single photon ionization of gas phase adenine and cytosine by means of vacuum ultraviolet synchrotron radiation coupled to a velocity map imaging electron/ion coincidence spectrometer. Both in-vacuum temperature-controlled oven and aerosol thermodesorption were successfully applied to promote the intact neutral biological species into the gas phase. The photoion yields are consistent with previous measurements. In addition, we deduced the threshold photoelectron spectra and the slow photoelectron spectra for both species, where the close to zero kinetic energy photoelectrons and the corresponding photoions are measured in coincidence. The photoionization close and above the ionization energies are found to occur mainly via direct processes. Both vaporization techniques lead to similar electronic spectra for the two molecules, which consist of broadbands due to the complex electronic structure of the cationic species and to the possible contribution of several neutral tautomers for cytosine prior to ionization. Accurate ionization energies are measured for adenine and cytosine at, respectively, 8.267 +/- 0.005 eV and 8.66 +/- 0.01 eV, and we deduce precise thermochemical data for the adenine radical cation. Finally, we performed an evaluation and a comparison of the two vaporization techniques addressing the following criteria: measurement precision, thermal fragmentation, sensitivity, and sample consumption. The aerosol thermodesorption technique appears as a promising alternative to vaporize large thermolabile biological compounds, where extended thermal decomposition or low sensitivity could be encountered when using a simple oven vaporization technique.

Touboul, D.; Gaie-Levrel, F.; Garcia, G. A.; Nahon, L.; Poisson, L.; Schwell, M.; Hochlaf, M.

2013-03-01

183

Vapor-phase molecular doping of graphene for high-performance transparent electrodes.  

PubMed

Doping is an essential process to engineer the conductivity and work-function of graphene for higher performance optoelectronic devices, which includes substitutional atomic doping by reactive gases, electrical/electrochemical doping by gate bias, and chemical doping by acids or reducing/oxidizing agents. Among these, the chemical doping has been widely used due to its simple process and high doping strength. However, it also has an instability problem in that the molecular dopants tend to gradually evaporate from the surface of graphene, leading to substantial decrease in doping effect with time. In particular, the instability problem is more serious for n-doped graphene because of undesirable reaction between dopants and oxygen or water in air. Here we report a simple method to tune the electrical properties of CVD graphene through n-doping by vaporized molecules at 70 °C, where the dopants in vapor phase are mildly adsorbed on graphene surface without direct contact with solution. To investigate the dependence on functional groups and molecular weights, we selected a series of ethylene amines as a model system, including ethylene diamine (EDA), diethylene triamine (DETA), and triethylene tetramine (TETA) with increasing number of amine groups showing different vapor pressures. We confirmed that the vapor-phase doping provides not only very high carrier concentration but also good long-term stability in air, which is particularly important for practical applications. PMID:24313602

Kim, Youngsoo; Ryu, Jaechul; Park, Myungjin; Kim, Eun Sun; Yoo, Je Min; Park, Jaesung; Kang, Jin Hyoun; Hong, Byung Hee

2014-01-28

184

SURVEY OF INDUSTRIAL APPLICATIONS OF VAPOR-PHASE ACTIVATED-CARBON ADSORPTION FOR CONTROL OF POLLUTANT COMPOUNDS FROM MANUFACTURE OF ORGANIC COMPOUNDS  

EPA Science Inventory

This study covers industrial use of activated carbon for vapor-phase applications. A listing of over 700 applications of vapor-phase carbon systems is made available for use in identifying sites where a given compound is being removed....

185

Transient-pressure analysis in geothermal steam reservoirs with an immobile vaporizing liquid phase  

USGS Publications Warehouse

A finite-difference model for the radial horizontal flow of steam through a porous medium is used to evaluate transient-pressure behavior in the presence of an immobile vaporizing or condensing liquid phase. Graphs of pressure drawdown and buildup in terms of dimensionless pressure and time are obtained for a well discharging steam at a constant mass flow rate for a specified time. The assumptions are made that the steam is in local thermal equilibrium with the reservoir rocks, that temperature changes are due only to phase change, and that effects of vapor-pressure lowering are negligible. Computations show that when a vaporizing liquid phase is present the pressure drawdown exhibits behavior similar to that observed in noncondensable gas reservoirs, but delayed in time. A theoretical analysis allows for the computation of this delay and demonstrates that it is independent of flow geometry. The response that occurs upon pressure buildup is markedly different from that in a noncondensable gas system. This result may provide a diagnostic tool for establishing the existence of phase-change phenomena within a reservoir. ?? 1979.

Moench, A. F.; Atkinson, P. G.

1978-01-01

186

Catalytic hydrodenitrogenation of quinoline in a trickle-bed reactor. Comparison with vapor phase reaction  

SciTech Connect

Studies over a commercial NiMo/Al/sub 2/O/sub 3/ catalyst at 350, 375, and 390/sup 0/C and 6.9 MPa using quinoline or various intermediate reaction products showed that the reaction rate constants for the various hydrodenitrogenation (HDN) reactions in the presence of an inert paraffin liquid are very similar to those for the same reactions in the vapor phase, although the liquid tends to equalize the adsorptivities of the various N-compounds present. Over a wide range, for a specified pressure and temperature, the percent conversion as a function of contact time is remarkably similar for liquid- and vapor-phase processing. In both cases, the overall HDN reaction is essentially zero order under the conditions studied. Equilibrium between quinoline and 1,2,3,4-tetrahydroquinoline is rapidly attained in both vapor-phase and liquid-phase processing. Homogeneous reactions were negligible except for the hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline.

Satterfield, C.N.; Yang, S.H.

1984-06-01

187

Vapor-phase and solution-phase UV spectroscopic studies of ? 5-pentadienyl derivatives of iron and ruthenium  

Microsoft Academic Search

The electronic absorption spectra of the ‘half-open metallocenes’, (Cp)(C7H11)Fe, (Cp)(C7H11)Ru, (Cp*)(C7H11)Ru (Cp=?5-cyclopentadienyl, Cp*=?5-pentamethylcyclopentadienyl, C7H11=?5-2,4-dimethylpentadienyl), and ‘open metallocenes’, (C7H11)2Fe, (C7H11)2Ru, have been measured in the vapor phase and in n-pentane solution and have been compared with the spectrum of the ‘closed ferrocene’ (Cp)(Cp*)Fe. The vapor-phase spectrum of (Cp)(Cp*)Fe reveals two sharp absorption bands arising from the 3dz2?R4s and 3dz2?R4d transitions. These

Sergey Yu Ketkov; Richard D Ernst; Lothar Stahl; Wimonrat Trakarnpruk

1998-01-01

188

Selective vapor phase sensing of small molecules using biofunctionalized field effect transistors  

NASA Astrophysics Data System (ADS)

This work details a proof of concept study for vapor phase selective sensing using a strategy of biorecognition elements (BRE) integrated into a zinc oxide field effect transistor (ZnO FET). ZnO FETs are highly sensitive to changes to the environment with little to no selectivity. Addition of a biorecognition element retains the sensitivity of the device while adding selectivity. The DNA aptamer designed to bind the small molecule riboflavin was covalently integrated into the ZnO FET and detects the presence of 116 ppb of riboflavin in a nitrogen atmosphere by a change in current. The unfunctionalized ZnO FET shows no response to this same concentrations of riboflavin, showing that the aptamerbinding strategy may be a promising strategy for vapor phase sensing.

Hagen, Joshua A.; Kim, Sang Nyon; Kelley-Loughnane, Nancy; Naik, Rajesh R.; Stone, Morley O.

2011-05-01

189

Mass Transport through the Carrier Gas Boundary Layer in Organic Vapor Phase Deposition  

NASA Astrophysics Data System (ADS)

We investigate the dynamics of molecular transport across the gas boundary layer formed above a cold substrate used in the organic vapor phase deposition of small organic molecules. The boundary layer properties ultimately determine film thickness uniformity and morphology, and material utilization efficiency. We use laser-induced fluorescence to spatially resolve the temperature and the concentration of organic molecules within the boundary layer. Under conditions typically used in organic vapor phase deposition of chamber pressures less than 5 torr, we find that the boundary layer extends to a remarkable distance of over 10 cm from the cooled substrate surface. Analytical and numerical models of molecular transport processes are developed to understand the transport of organic molecules to the substrate. Our models provide insights into conditions required to optimize film uniformity and material utilization efficiency in the growth of organic electronic devices.

Rolin, Cedric; Song, Byeongseop; Forrest, Stephen R.

2014-04-01

190

Combined hydride and metal organic vapor-phase epitaxy of GaN on sapphire  

NASA Astrophysics Data System (ADS)

We describe a method to produce GaN epitaxial layers in a single chamber where a low-temperature buffer layer is deposited using metalorganic vapor-phase epitaxy (MOVPE), followed by conventional hydride vapor-phase epitaxy (HVPE) of GaN at higher temperatures. While a typical 12 ?m sample is investigated here, the GaN film thickness can vary between 2 and 200 ?m, with HVPE growth rate ranging from 5 to 60 ?m/h. Cross-sectional transmission-electron microscope images show a dense network of mixed dislocations, whose density is significantly reduced after 6 ?m to the high 107 cm-2 range. 10 K photoluminescence shows bound exciton dominated emission associated with the A and B valence bands and phonon replicas. No yellow emission is observed. This versatile process can be extended to produce additional device layers by MOVPE.

Solomon, G. S.; Miller, D. J.; Ramsteiner, M.; Trampert, A.; Brandt, O.; Ploog, K. H.

2005-10-01

191

Melting, ablation, and vapor phase condensation during atmospheric passage of the Bjurbole meteorite  

NASA Technical Reports Server (NTRS)

A detailed study of the Bjurbole fusion crust using scanning electron microscopy (SEM) and energy dispersive analysis (EDS) shows that filamentary crystals and ablation spheres may form on the meteoroid surface. Filamentary crystals, hollow spheres, and porous regions of the surface point to a period of intense vapor phase activity during atmospheric passage. Filamentary crystals can be divided into three categories on the basis of bulk composition and morphology. Two types of filamentary crystals are vapor phase condensation products formed during atmospheric entry of the meteoroid. The other type forms by the interaction of seawater with the fusion surface. The density and composition of ablation spheres varies with the flight orientation of the meteorite. The size range and composition of iron-nickel spheres on the surface of Bjurbole are similar to spheres collected in the stratosphere. A comparison of stratospheric dust collections with meteorite surfaces may provide further insight into the mechanisms of meteoroid entry into planetary atmospheres.

Rietmeijer, F. J. M.; Mackinnon, I. D. R.

1984-01-01

192

Sintering behavior of ultrafine silicon carbide powders obtained by vapor phase reaction  

NASA Technical Reports Server (NTRS)

The sintering behavior of ultrafine SiC powder with average particle size of about 0.01-0.06 microns produced by a vapor phase reaction of the Me4Si-H2 system was studied at the temperature range of 1400-2050 deg. It was found that the homogeneous dispersion of C on SiC particles is important to remove the surface oxide layer effectively. B and C and inhibitive effect on SiC grain growth.

Okabe, Y.; Miyachi, K.; Hojo, J.; Kato, A.

1984-01-01

193

Fabricating PC\\/PAN composite membranes by vapor-induced phase separation  

Microsoft Academic Search

In this study, a series of polycarbonate\\/polyacrylonitrile (PC\\/PAN) composite membrane has been successfully fabricated by vapor-induced phase separation and in-situ casting process. The effect of the casting solution concentration on the membrane morphology was investigated. The morphology of the PC\\/PAN composite membranes was characterized by SEM. The effect of the skin layer thickness on the water flux was measured at

S. T. Kao; M. Y. Teng; C. L. Li; C. Y. Kuo; C. Y. Hsieh; H. A. Tsai; D. M. Wang; K. R. Lee; J. Y. Lai

2008-01-01

194

Phase composition and morphology of TaC coating on carbon fibers by chemical vapor infiltration  

Microsoft Academic Search

Chemical vapor infiltration was applied to deposit TaC thin film on carbon fibers using TaCl5–Ar–C3H6–H2 source. The influence of temperature, pressure and addition of H2 on phase composition and morphology of the coating had been studied. The results showed that the composition of the coating changes with temperature. The films are mainly composed of TaC and C when deposited at

Zhao-ke Chen; Xiang Xiong; Bai-yun Huang; Guo-dong Li; Feng Zheng; Peng Xiao; Hong-bo Zhang; Jian Yin

2008-01-01

195

Evidence of critical scaling behavior during vapor phase synthesis of continuous filament composites  

SciTech Connect

We present experimental measurements of the accessible pore fraction in ceramic matrix composites during consolidation by vapor phase infiltration. For two topologically distinct filament architectures, the accessible pore fraction decreased during consolidation with a power law decay and a critical scaling exponent of 0.41 ( R{sup 2}=0.97). A three-dimensional analysis of the percolating pores revealed that the structures became topologically equivalent and simply connected near the critical density. {copyright} {ital 1997 Materials Research Society.}

Kinney, J.H.; Haupt, D.L. [Chemistry and Materials Science Department, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

1997-03-01

196

Preparation of Symmetric Network PVDF Membranes for Protein Adsorption via Vapor-Induced Phase Separation  

Microsoft Academic Search

Symmetric network poly(vinylidene fluoride) (PVDF) membranes without a dense skin layer were prepared by vapor-induced phase separation from a PVDF\\/N,N-dimethylacetamide (DMAc)\\/water system. The effects of evaporation atmosphere, temperature, and humidity during the preparation of the membranes on their morphologies were investigated by scanning electron microscope (SEM). With low temperature and high humidity, the polymer crystallization mechanism dominated the membrane formation

Qian Ye; Lihua Cheng; Lin Zhang; Li Xing; Huanlin Chen

2011-01-01

197

Preparation of symmetric network PVDF membranes for protein adsorption via vapor induced phase separation  

Microsoft Academic Search

Symmetric network poly(vinylidene fluoride) (PVDF) membranes without a dense skin layer were prepared by vapor induced phase separation from a PVDF\\/ N,N-dimethyl acetamide (DMAc)\\/ water system. The effects of evaporation atmosphere, temperature and humidity during the preparation of the membranes on their morphologies were investigated by SEM. With low temperature and high humidity, the polymer crystallization mechanism dominated the membrane

Qian Ye; Lihua Cheng; Lin Zhang; Li Xing; Huanlin Chen

2011-01-01

198

Solid-State Chemosensitive Organic Devices for Vapor-Phase Detection  

Microsoft Academic Search

This chapter surveys the wide range of technologies available for vapor-phase chemical sensing, highlighting the developments\\u000a in the state-of-the-art solid-state sensors. In addition, recent advances in lasing to enhance the sensitivity of fluorescent\\u000a conjugated polymer sensors are treated in detail. A brief discussion of chemosensing heterojunction photoconductors and the\\u000a benefits of this novel sensor platform conclude the chapter.

J. Ho; A. Rose; T. Swager; V. Bulovi?

199

Strain variation with sample thickness in GaN grown by hydride vapor phase epitaxy  

Microsoft Academic Search

High quality GaN crystals can be grown on sapphire by hydride vapor phase epitaxy. The thermal expansion mismatch between sapphire and GaN produces strain in the GaN crystal as it is cooled from the growth temperature to room temperature. The strain is evidenced by shifts in the photoluminescence and reflectance line positions. By analyzing the surface strain as the crystal

D. C. Reynolds; D. C. Look; B. Jogai; J. E. Hoelscher; R. E. Sherriff; R. J. Molnar

2000-01-01

200

Removal of Oxygen from Electronic Materials by Vapor-Phase Processes  

NASA Technical Reports Server (NTRS)

Thermochemical analyses of equilibrium partial pressures over oxides with and without the presence of the respective element condensed phase, and hydrogen, chalcogens, hydrogen chalcogenides, and graphite are presented. Theoretical calculations are supplemented with experimental results on the rate of decomposition and/or sublimation/vaporization of the oxides under dynamic vacuum, and on the rate of reaction with hydrogen, graphite, and chalcogens. Procedures of removal of a number of oxides under different conditions are discussed.

Palosz, Witold

1997-01-01

201

Vertical cavity surface emitting laser with 21% efficiency by metalorganic vapor phase epitaxy  

SciTech Connect

Proton implanted, vertical cavity top-surface emitting lasers exhibit the highest single-mode and multi-mode output powers, highest power conversion efficiency, and lowest threshold voltage for such devices reported to date. These lasers use new mirror grading designs that are enabled by metalorganic vapor phase epitaxy's capabilities of alloy grading and carbon doping. The results validate this growth technology by exceeding the previous best results which were based on molecular beam epitaxy.

Lear, K.L.; Schneider, R.P.; Choquette, K.D.; Kilcoyne, S.P.; Figiel, J.J.; Zolper, J.C. (Sandia National Labs., Albuquerque, NM (United States))

1994-09-01

202

Vertical cavity surface emitting lasers with 21% efficiency by metalorganic vapor phase epitaxy  

Microsoft Academic Search

Proton implanted, vertical cavity top-surface emitting lasers exhibit the highest single-mode and multi-mode output powers, highest power conversion efficiency, and lowest threshold voltage for such devices reported to date. These lasers use new mirror grading designs that are enabled by metalorganic vapor phase epitaxy's capabilities of alloy grading and carbon doping. The results validate this growth technology by exceeding the

K. L. Lear; R. P. Schneider; K. D. Choquette; S. P. Kilcoyne; J. J. Figiel; J. C. Zolper

1994-01-01

203

Vapor-phase addition of methanol to isobutene on a macroporous resin; A kinetic study  

Microsoft Academic Search

The authors describe a study of the kinetics of the vapor-phase addition of methanol to isobutene to give methyl tert-butyl ether (MTBE) on the ion-exchange resin Amberlyst 15. Rate data were obtained in a continuous differential reactor operated at atmospheric pressure and 41-61.5°C. The best-fitting Langmuir-Hinshelwood-Hougen-Watson (LHHW) rate equation is derived from a mechanism whose rate-determining step is the reaction

Javier Tejero; Fidel Cunill; Jose F. Izquierdo

1989-01-01

204

Rolling Contact Testing of Vapor Phase Lubricants–Part I: Material Evaluation  

Microsoft Academic Search

Material screening tests have been performed with four candidate vapor phase lubricants under rolling contact conditions at bearing test temperatures of 370°C. The lubricants evaluated were t-butyl phenyl phosphate (TBPP), polyalphaolefin (PAO), cyclophosphazene (X-1P), and PAO blended with 15 percent TBPP (PAO+). Factorial analyses were used to separate the effects of lubricant; bearing steel, T15 vs. thin dense chrome-coated T15;

Nelson H. Forster; Hitesh K. Trivedi

1997-01-01

205

Vapor phase hydrogenation of o -chloronitrobenzene ( o -CNB) over alumina supported palladium catalyst — a kinetic study  

Microsoft Academic Search

Kinetics of the vapor phase hydrogenation of o-chloronitrobenzene (o-CNB) over Pd\\/Al2O3 catalyst has been studied in a downflow microreactor under atmospheric pressure. Reaction rates have been measured at three\\u000a different temperatures with respect to the partial pressures of o-CNB and hydrogen. The order of the reaction with respect to o-CNB was 0.53 at 280?C and increased with increasing temperature. However,

Venkataraman Vishwanathan; V. Jayasri; P. Mahaboob Basha

2007-01-01

206

Concentration dependent Zn diffusion in InP during metalorganic vapor phase epitaxy  

Microsoft Academic Search

Concentration dependent diffusion of Zn during metalorganic vapor phase epitaxy from a Zn-doped InP layer into the adjacent undoped InP buffer layer were studied systematically using secondary ion mass spectroscopy and carrier concentration profiling. Under the condition that the growth rate of the Zn-doped film is faster than the interdiffusion of Zn into the underlying undoped buffer layer, the diffusion

S. N. G Chu; R. A. Logan; M. Geva; N. T. Ha

1995-01-01

207

Thermal conductivity of refrigerant R-415A in the vapor phase  

NASA Astrophysics Data System (ADS)

Thermal conductivity of refrigerant R-415A in the vapor phase has been studied by the steady-state method of coaxial cylinders in the range of temperatures 308-415 K and pressures 0.12-1.68 MPa. The approximation dependence of thermal conductivity on pressure and temperature was determined. Thermal conductivity on the dew line and in the ideal gas state was calculated.

Verba, O. I.; Raschektaeva, E. P.; Stankus, S. V.

2013-12-01

208

AlGaAs epitaxial growth on (111)B substrates by metalorganic vapor-phase epitaxy  

Microsoft Academic Search

AlGaAs epitaxial layers were grown on (111)B-oriented GaAs substrates by metalorganic vapor-phase epitaxy (MOVPE). Mirrorlike surfaces can be obtained with a growth temperature of 875–900 °C and a V\\/III ratio of 10–20, while a high density of hillocks appears with lower temperatures and\\/or larger V\\/III ratios. Hillock density is reduced by introducing misorientation on (111)B substrates. In this case, however,

Kazutoshi Kato; Yuji Hasumi; Atsuo Kozen; Jiro Temmyo

1989-01-01

209

Radioiodination of interleukin 2 to high specific activities by the vapor-phase chloramine T method  

SciTech Connect

Recombinant human interleukin 2 (IL-2) was radioiodinated utilizing the vapor phase chloramine T method of iodination. The method is rapid, reproducible, and allows the efficient radioiodination of IL-2 to specific activities higher than those previously attained with full retention of biological activity. IL-2 radioiodinated by this method binds with high affinity to receptors present on phytohemagglutinin-stimulated peripheral blood lymphocytes and should be useful for the study of receptor structure and function.

Siekierka, J.J.; DeGudicibus, S.

1988-08-01

210

Solid-State Chemosensitive Organic Devices for Vapor-Phase Detection  

NASA Astrophysics Data System (ADS)

This chapter surveys the wide range of technologies available for vapor-phase chemical sensing, highlighting the developments in the state-of-the-art solid-state sensors. In addition, recent advances in lasing to enhance the sensitivity of fluorescent conjugated polymer sensors are treated in detail. A brief discussion of chemosensing heterojunction photoconductors and the benefits of this novel sensor platform conclude the chapter.

Ho, J.; Rose, A.; Swager, T.; Bulovi?, V.

211

Phenothiazine-based oligomers as novel fluorescence probes for detecting vapor-phase nitro compounds.  

PubMed

To meet the need for rapid and low-cost chemical sensing of explosive, new fluorescence chemosensors based on oligophenothiazines for probing vapor-phase nitro compounds have been developed. The phenothiazine-based trimer P3 and pentamer P5 have been synthesized via Heck and Wittig reactions by convergent approach. It was found that they can detect the vapors of nitro compounds, including p-nitrotoluene (p-NT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT) with good sensitivity and reversibility. And the sensor of P3 film gave a linear fluorescence quenching response to 7-800 ppb TNT with the detection limit of 4 ppb. For DNT vapor, a linear working range of the sensor was 2-24 ppm with the detection limit of 40 ppb. Meanwhile, the interferents, including common organic solvents, p-nitrophenol and 2,4-dinitrophenylhydrazine cannot lead to obvious fluorescence quenching, meaning that the film based on oligophenothiazines exhibited good specificity of fluorescence response to explosive. Based on the fluorescence lifetime and UV-vis absorption measurements, we suggested that the fluorescence quenching of oligophenothiazine-based films exposed to the vapors of nitro compounds was due to the formation of non-fluorescent charge-transfer complex between oligophenothiazine and nitro compounds. PMID:20875600

Zhang, Xiaofei; Qiu, Xianping; Lu, Ran; Zhou, Huipeng; Xue, Pengchong; Liu, Xingliang

2010-10-15

212

Use of methylselenol for organometallic vapor-phase epitaxy of ZnSe  

NASA Astrophysics Data System (ADS)

Heteroepitaxial films of ZnSe on GaAs substrates have been grown by atmospheric-pressure organometallic vapor-phase epitaxy using a new selenium source, methylselenol, CH 3SeH (MSeH). Gas-phase prereaction with a group-II source material was suppressed compared with hydride sources, e.g., H 2Se. The practical growth temperature was 300-400°C, which was sufficiently lower than 500°C used in the growth with dialkyl compounds. The epilayers exhibited a fairly smooth surface morphology and good crystallographic properties. Higher quality epilayers can be expected with source repurification or synthesis via purer chemical processes.

Fujita, Shizuo; Sakamoto, Takao; Isemura, Masashi; Fujita, Shigeo

1988-03-01

213

Phase separation in InGaN grown by metalorganic chemical vapor deposition  

NASA Astrophysics Data System (ADS)

We report on phase separation in thick InGaN films with up to 50% InN grown by metalorganic chemical vapor deposition from 690 to 780 °C. InGaN films with thicknesses of 0.5 ?m were analyzed by ?-2? x-ray diffraction, transmission electron microscopy (TEM), and selected area diffraction (SAD). Single phase InGaN was obtained for the as-grown films with <28% InN. However, for films with higher than 28% InN, the samples showed a spinodally decomposed microstructure as confirmed by TEM and extra spots in SAD patterns that corresponded to multiphase InGaN.

El-Masry, N. A.; Piner, E. L.; Liu, S. X.; Bedair, S. M.

1998-01-01

214

Introducing phase transitions to quantum chemistry: from Trouton's rule to first principles vaporization entropies.  

PubMed

In the present study, we employ quantum cluster equilibrium calculations on a small water cluster set in order to derive thermochemical equilibrium properties of the liquid phase as well as the liquid-vapor phase transition. The focus is set on the calculation of liquid phase entropies, from which entropies of vaporization at the normal boiling point of water are derived. Different electronic structure methods are compared and the influences of basis set size and of cooperative effects are discussed. In line with a previous study on the subject [B. Kirchner, J. Chem. Phys. 123, 204116 (2005)], we find that the neglect of cooperativity leads to large errors in the equilibrium cluster populations as well as in the obtained entropy values. In contrast, a correct treatment of the intermolecular many-body interaction yields liquid phase entropies and phase transition entropies being in very good agreement with the experimental reference, thus demonstrating that the quantum cluster equilibrium partition function intrinsically accounts for the shortcomings of the ideal gas partition function often employed in first principles entropy calculations. Comparing the calculated vaporization entropies to the value predicted by Trouton's rule, it is observed that for entropy calculations the consideration of intracluster cooperative effects is more important than the explicit treatment of the intercluster association even in a highly associated liquid such as water. The decomposition of entropy into contributions due to different degrees of freedom implies the need for the accurate treatment of particle indistinguishability and free volume of translation, whereas minor influences should be expected from the vibrational and rotational degrees of freedom and none from the electronic degrees of freedom. PMID:18618941

Spickermann, Christian; Lehmann, Sebastian B C; Kirchner, Barbara

2008-06-28

215

System for Bulk Growth of Gallium Nitride. Vapor Phase Epitaxy of Gallium Nitride by Gallium Arc Evaporation.  

National Technical Information Service (NTIS)

A vapor phase growth system intended for the growth of bulk gallium nitride crystals was investigated. Potential advantages of the growth technique are cheap source materials of high purity, no corrosive gasses, and low operating and equipment costs. Ga c...

S. J. Heikman U. K. Mishra

2005-01-01

216

Enhanced Vapor-Phase Diffusion in Porous Media - LDRD Final Report  

SciTech Connect

As part of the Laboratory-Directed Research and Development (LDRD) Program at Sandia National Laboratories, an investigation into the existence of enhanced vapor-phase diffusion (EVD) in porous media has been conducted. A thorough literature review was initially performed across multiple disciplines (soil science and engineering), and based on this review, the existence of EVD was found to be questionable. As a result, modeling and experiments were initiated to investigate the existence of EVD. In this LDRD, the first mechanistic model of EVD was developed which demonstrated the mechanisms responsible for EVD. The first direct measurements of EVD have also been conducted at multiple scales. Measurements have been made at the pore scale, in a two- dimensional network as represented by a fracture aperture, and in a porous medium. Significant enhancement of vapor-phase transport relative to Fickian diffusion was measured in all cases. The modeling and experimental results provide additional mechanisms for EVD beyond those presented by the generally accepted model of Philip and deVries (1957), which required a thermal gradient for EVD to exist. Modeling and experimental results show significant enhancement under isothermal conditions. Application of EVD to vapor transport in the near-surface vadose zone show a significant variation between no enhancement, the model of Philip and deVries, and the present results. Based on this information, the model of Philip and deVries may need to be modified, and additional studies are recommended.

Ho, C.K.; Webb, S.W.

1999-01-01

217

Vapor-phase synthesis of mesoporous SiO2-P2O5 thin films.  

PubMed

Mesoporous SiO2-P2O5 films were synthesized from the vapor phase onto a silicon substrate. First, a precursor solution of cetyltrimethylammonium bromide (C16TAB), H3PO4, ethanol, and water was deposited on a silicon substrate by a spin-coating method. Then, the C16TAB-H3PO4 composite film was treated with tetraethoxysilane (TEOS) vapor at 90-180 degrees C for 2.5 h. The H3PO4-C16TAB composite formed a hexagonal structure on the silicon substrate before vapor treatment. The TEOS molecules penetrated into the film without a phase transition. The periodic mesostructure of the SiO2-P2O5 films was retained after calcination. The calcined films showed a high proton conductivity of about 0.55 S/cm at room temperature. The molar ratio of P/Si in the SiO2-P2O5 film was as high as 0.43, a level that was not attained by a premixing sol-gel method. The high phosphate group content and the ordered periodic mesostructure contributed to the high proton conductivity. PMID:17373837

Nishiyama, Norikazu; Kaihara, Junji; Nishiyama, Yuko; Egashira, Yasuyuki; Ueyama, Korekazu

2007-04-24

218

Ordered organic thin films self-assembled from the vapor phase  

NASA Technical Reports Server (NTRS)

Organic films self-assembled from a liquid phase, as in Langmuir-Blodgett or adsorption from solution, have received much attention in the past decade as techniques to achieve highly oriented-ordered polymeric thin films. Many organic compounds including some of the same fatty acids have been vapor deposited as well. However, organic pigments and dyes comprise a major class of important materials which have very low solubilities yet excellent thermal stabilities, making them ideally suited for film deposition from the vapor phase. Surprisingly, such molecular systems exhibit a significant propensity to self order, a high sensitivity to deposition parameters, and a range of microstructural forms that cannot be duplicated by the less energetic mechanisms associated with solution adsorption processes. Molecular solids such as heterocyclic polynuclear aromatics are excellent candidates for film formation by vacuum deposition means. Over the past decade, our work and that of others investigating a wide variety of perylene and phthalocyanine derivatives identified five deposition parameters that can significantly affect film morphology, physical microstructure, and type and extent of ordering developed in vacuum and vapor transport grown films. These parameters are substrate temperature, deposition rate, substrate chemistry and epitaxy, ambient gas convective flows, and post deposition annealing. Examples of how each of these conditions manifest themselves in the film structure and ordering, most frequently revealed by scanning electron microscopy, reflection absorption infrared spectroscopy (RAIR), and grazing incidence x-ray diffraction (GIX), are presented.

Debe, M. K.

1993-01-01

219

Structural properties of TiO2 nanocrystallites condensed in vapor-phase for photocatalyst applications  

NASA Astrophysics Data System (ADS)

We have synthesized titanium dioxide (TiO2) nanocrystallites by pulsed laser ablation (PLA) in oxygen (O2) background gas for photocatalyst applications. Varying O2 background gas pressure ( {P_{{{O}_{ 2} }} } ) or substrate target distance (D TS), it was possible to change weight fraction of anatase phase in the anatase/rutile mixture from 0.2 to 1.0. Porosity of the deposited TiO2 films increased with increasing ( {P_{{{O}_{ 2} }} } ) and D TS. Relation between the process parameters and the formed crystal phases was explained from the point of cooling process in vapor-phase. Furthermore, rapid thermal annealing (RTA) was performed as post-annealing, suppressing sintering of the nanocrystallites. Photocatalytic activities of the TiO2 nanocrystallites depended on the RTA temperature and following crystallinity restoring as well as the crystal phase: anatase or rutile.

Yoshida, Takehito; Yagi, Nobuyasu; Nakagou, Riki; Sugimura, Akira; Umezu, Ikurou

2014-03-01

220

a-plane GaN grown on r-plane sapphire substrates by hydride vapor phase epitaxy  

Microsoft Academic Search

Thin a-plane ( 112¯0) GaN layers have been grown on r-plane ( 11¯02) sapphire substrates by hydride vapor phase epitaxy (HVPE), using either a single-step high-temperature (HT) growth or a two-step growth method similar to that of metal organic vapor phase epitaxy (MOVPE). For the single-step growth procedure, layers were grown under various pressures, ranging from near atmospheric pressure down

T. Zhu; D. Martin; R. Butté; J. Napierala; N. Grandjean

2007-01-01

221

Vapor-phase fabrication and properties of continuous-filament ceramic composites.  

PubMed

The continuous-filament ceramic composite is becoming recognized as necessary for new, high-temperature structural applications. Yet because of the susceptibility of the filaments to damage from traditional methods for the preparation of ceramics, vapor-phase infiltration has become the fabrication method of choice. The chemical vapor infiltration methods for producing these composites are now being studied in earnest, with the complexity of filament weaves and deposition chemistry being merged with standard heat and mass-transport relationships. Two of the most influential effects on the mechanical properties of these materials are the adhesion and frictional force between the fibers and the matrix, which can be controlled by a tailored interface coating. A variety of materials are available for producing these composites including carbide, nitride, boride, and oxide filaments and matrices. Silicon carbide-based materials are by far the most advanced and are already being used in aerospace applications. PMID:17731807

Besmann, T M; Sheldon, B W; Lowden, R A; Stinton, D P

1991-09-01

222

Interfacial Phase Transitions at Solid-Fluid and Liquid-Vapor Interfaces  

NASA Astrophysics Data System (ADS)

To study the interface between a solid surface and nitrogen vapor, the theory of Cahn was applied. The Peng-Robinson equation of state (PREOS) was incorporated in the theory of Cahn to model the thermodynamic functions of the fluid. In this study the wetting transition, as earlier reported by Cahn, was shown. In addition, wetting transitions occurring at a liquid-vapor interface of the three-phase LLV equilibrium of the binary mixtures hexane/water and benzene/water were examined. It was found that by making use of the gradient theory of van der Waals, in which the PREOS was incorporated, the transitions seem to be of third order. For the case where the PREOS was replaced by the Associated-Perturbed-Anisotropic-Chain-Theory, no wetting region was found. It was argued that, in principle, it should he possible to model first-order wetting transitions with the square gradient theory.

Cornelisse, P. M. W.; Peters, C. J.; de Swaan Arons, J.

1998-11-01

223

Fabrication of MEMS devices by using anhydrous HF gas-phase etching with alcoholic vapor  

NASA Astrophysics Data System (ADS)

In silicon surface micromachining, anhydrous HF GPE process was verified as a very effective method for the dry release of microstructures. The developed gas-phase etching (GPE) process with anhydrous hydrogen fluoride (HF) gas and alcoholic vapor such as methanol, isopropyl alcohol (IPA) was characterized and its selective etching properties were discussed. The structural layers are P-doped multi-stacked polysilicon and silicon-on-insulator (SOI) substrates and sacrificial layers are tetraethylorthosilicate (TEOS), low-temperature oxide (LTO), plasma enhanced chemical vapor deposition (PECVD) oxide, phosphosilicate glass (PSG) and thermal oxides on silicon nitride or polysilicon substrates. We successfully fabricated and characterized micro electro mechanical system (MEMS) devices with no virtually process-induced stiction and no residues. The characteristics of the MEMS devices for microsensor and microactuator, microfluidic elements and optical MEMS application were evaluated by experiment.

Ick Jang, Won; Auck Choi, Chang; Lee, Myung Lae; Jun, Chi Hoon; Kim, Youn Tae

2002-05-01

224

Properties of nuclear waste melts and glasses: Contact-refractory corrosion and vapor phase hydration  

NASA Astrophysics Data System (ADS)

Control of refractory corrosion in waste glass melts and meeting vapor phase hydration test (VHT) requirement for Hanford low-activity waste (LAW) glass product are two critical issues among many technical challenges of nuclear waste vitrification. In this study, refractory corrosion was treated as a complex non-equilibrium, multi-component and multi-phase reactive transport process and studied both thermodynamically and kinetically. Dissolution tests of granular refractory materials into under-saturated melts coupled with crystallization tests from supersaturated melts were used to determine the possible equilibrium points. The test results show that spinet phase is the most stable phase of K-3 refractory. Solubility of glass-refractory interface material controls the long term refractory corrosion rate and protects refractory from further corrosion. Therefore, refractory corrosion rate can be possibly adjusted by controlling the underlying solubility of the interface material. A set of monolithic refractory corrosion and dissolution tests was carried out to study the kinetic effects of refractory porosity and glass melt viscosity, the two major kinetic factors associated with reactive transport process. The test results show that temperature and glass melt viscosity have intensive effects on refractory material dissolution rate. Fast closure of channels near the glass-refractory interface during corrosion reaction by fast transformation of solid solution to spinel and spinel re-crystallization helps stop further corrosion reaction. Glass composition can be "passivated" by engineering the formulation to maximizing the beneficial alteration process. For the study of VHT kinetics, data from simulated LAW glasses studied previously at Pacific Northwest National Laboratory and Vitreous State Laboratory was modeled based on Avrami equation and its variant, the so-called generalized Avrami equation for better modeling of the VHT data. The results show that the kinetics of the complex vapor hydration process is described satisfactorily by the generalized Avrami equation. The generalized Avrami equation allows the characterization of vapor phase hydration data obtained at different times and temperatures quantitatively on a common basis. The three parameters associated with the generalized Avrami equation depend strongly on glass composition. It seems that both compositional mismatch and incompatibility of a host glass to the transformed hydrous crystalline phases slow down the vapor hydration rate.

Lu, Xiaodong

225

Vapor-Phase Garnet at Yucca Mountain, Nevada: Geochemistry and Oxygen-Isotope Thermometry  

SciTech Connect

About 20 vapor-phase garnets were studied in two samples of the Topopah Spring Tuff from Yucca Mountain, in southern Nevada. The Miocene-age Topopah Spring Tuff is a 350-m-thick, devitrified, moderately to densely welded ash flow that is compositionally zoned from high-silica rhyolite to quartz latite. During cooling of the tuff, escaping vapor produced lithophysae (former gas cavities) lined with an assemblage of tridymite, cristobalite, alkali feldspar, and locally, hematite and/or garnet. Vapor-phase topaz and economic deposits (such as porphyry molybdenum-tungsten) commonly associated with topaz-bearing rhyolites (characteristically enriched in fluorine) were not found in the Topopah Spring Tuff at Yucca Mountain. The garnets are not primary igneous phenocrysts, but rather crystals that grew from a fluorine-poor magma-derived vapor trapped during emplacement of the tuff. The garnets are euhedral, vitreous, reddish brown, trapezohedral, as large as 2 mm in diameter, and fractured. The garnets also contain inclusions of tridymite. Electron-microprobe analyses of the garnets reveal that they are almandine-spessartine (48.0 and 47.9 mol percent, respectively), have an average chemical formula of (Fe{sub 1.46}, Mn{sub 1.45}, Mg{sub 0.03}, Ca{sub 0.10}) (Al{sub 1.93}, TiO{sub 0.02}) Si{sub 3.01}O{sub 12}, and are homogeneous in Fe and Mn concentrations from core to rim. Composited garnets from each sample site have {delta}{sup 18}O values of 7.2 and 7.4{per_thousand}. The coexisting tridymite, however, has {delta}{sup 18}O values of 17.4 and 17.6{per_thousand} values indicative of reaction with later, low-temperature water. Unaltered tridymite from higher in the stratigraphic section has a {delta}{sup 18}O of 11.1{per_thousand} which, when coupled with the garnet {delta}{sup 18}O values in a quartz-garnet fractionation equation, indicates vapor-phase crystallization at temperatures of almost 600 C. This high-temperature mineralization, formed during cooling of the tuffs, is distinct from the later and commonly recognized low-temperature stage (generally 50-70 C) of calcite, quartz, and opal secondary mineralization, formed from percolating meteoric water, that locally coats fracture footwalls and lithophysal floors.

R. J. Moscati; C.A. Johnson; J.F. Whelan

2001-07-03

226

Reduced exposure evaluation of an Electrically Heated Cigarette Smoking System. Part 2: Smoke chemistry and in vitro toxicological evaluation using smoking regimens reflecting human puffing behavior.  

PubMed

Chemical analysis of up to 49 harmful and potentially harmful constituents (HPHC) in mainstream smoke, in vitro cytotoxicity of the particulate and gas/vapor phase of mainstream smoke determined in the Neutral Red Uptake assay, and in vitro bacterial mutagenicity of the particulate phase determined in the Salmonella typhimurium Reverse Mutation (Ames) assay are reported for three Electrically Heated Cigarette Smoking System (EHCSS) series-K cigarettes, the University of Kentucky Reference Cigarette 2R4F, and a number of comparator commercial conventional lit-end cigarettes (CC) under ISO machine-smoking conditions and a total of 25 additional smoking regimens reflecting 'human puffing behavior' (HPB). The smoking machines were set to deliver nicotine yields for the EHCSS and comparator CC derived from the 10th percentile to the 90th percentile of nicotine uptake distributions in smokers determined in two clinical studies. Duplication of the smoking intensity 'per cigarette' on a smoking machine may provide an insight into product performance that is directly relevant to obtaining scientific evidence for reduced exposure substantiation based on mainstream cigarette smoke HPHC-to-nicotine regressions. The reported data support an overall evaluation of reduced exposure to HPHC and biological activity. PMID:22922180

Zenzen, Volker; Diekmann, Joerg; Gerstenberg, Birgit; Weber, Susanne; Wittke, Sandra; Schorp, Matthias K

2012-11-01

227

Gas-Phase and Surface Reactions in Xenon Lamp-Assisted Organometallic Vapor-Phase Epitaxy of ZnSe  

NASA Astrophysics Data System (ADS)

In this paper, the influence of xenon lamp irradiation on gas-phase and surface reactions in organometallic vapor-phase epitaxy of ZnSe on GaAs is investigated. The irradiation only to the gas phase scarcely influences the growth rate, while irradiation to the growth surface is essential for growth rate enhancement. Numbers of incident photons and those of adhered molecules are found to be of the same order, i.e., most photons irradiated onto the substrate are associated with the epitaxial growth. The above experimental results strongly suggest that incident photons enhance some surface reactions, resulting in higher growth rates and lower growth temperatures compared with those reactions occuring under no irradiation.

Fujita, Shizuo; Takeuchi, Fumiyo Y.; Fujita, Shigeo

1988-11-01

228

Infrared spectroscopic studies of the conformation in ethyl ?-haloacetates in the vapor, liquid and solid phases  

NASA Astrophysics Data System (ADS)

Infrared spectra of ethyl ?-fluoroacetate, ethyl ?-chloroacetate, ethyl ?-bromoacetate and ethyl ?-iodoacetate have been measured in the solid, liquid and vapor phases in the region 4000-200 cm -1. Vibrational frequency assignment of the observed bands to the appropriate modes of vibration was made. Calculations at DFT B3LYP/6-311+G** level, Job: conformer distribution, using Spartan program '08, release 132 was made to determine which conformers exist in which molecule. The results indicated that the first compound exists as an equilibrium mixture of cis and trans conformers and the other three compounds exist as equilibrium mixtures of cis and gauche conformers. Enthalpy differences between the conformers have been determined experimentally for each compound and for every phase. The values indicated that the trans of the first compound is more stable in the vapor phase, while the cis is the more stable in both the liquid and solid phases. In the other three compounds the gauche is more stable in the vapor and liquid phases, while the cis conformer is the more stable in the solid phase for each of the second and third compound, except for ethyl ?-iodoacetate, the gauche conformer is the more stable over the three phases. Molar energy of activation Ea and the pseudo-thermodynamic parameters of activation ? H‡, ? S‡ and ? G‡ were determined in the solid phase by applying Arrhenius equation; using bands arising from single conformers. The respective Ea values of these compounds are 5.1 ± 0.4, 6.7 ± 0.1, 7.5 ± 1.3 and 12.0 ± 0.6 kJ mol -1. Potential energy surface calculations were made at two levels; for ethyl ?-fluoroacetate and ethyl ?-chloroacetate; the calculations were established at DFT B3LYP/6-311+G** level and for ethyl ?-bromoacetate and ethyl ?-iodoacetate at DFT B3LYP/6-311G* level. The results showed no potential energy minimum exists for the gauche conformer in ethyl ?-fluoroacetate.

Jassem, Naserallah A.; El-Bermani, Muhsin F.

2010-07-01

229

Vaporizing Vapor  

NSDL National Science Digital Library

In this demonstration, relative humidity is modeled using a sponge and a pan of water, and the concept of saturation is depicted. Students answer questions examining the relationship between temperature and the capacity of air to hold water vapor. The resource is part of the teacher's guide accompanying the video, NASA Sci Files: The Case of the Phenomenal Weather. Lesson objectives supported by the video, additional resources, teaching tips and an answer sheet are included in the teacher's guide.

230

Pin-in-paste DFM constraints in vapor phase soldering technology for optoelectronic components  

NASA Astrophysics Data System (ADS)

The topical trends in the field of electronic equipments developing are a large integration on pcb support for different types of components and devices, including optoelectronic type, from small to medium power, in condition of reducing physical dimensions, in order to create new electronic products in short time at lower manufacturing cost. The condition for economical success for a product is to assure the product, even from the conception stage, with a high level of quality by reducing the product cost; to conclude, designing according with production possibilities by using Design For Manufacturing (DFM) concept. This desideratum depends on the conception and design of the product. According to DFM concept, a successful project assures design requirements for the system and finally for printed circuit boards (PCB), accomplishes the assembling technology constraints defined by international standards in the field of electronic packaging, such as IPC or Restriction of Hazardous Substances Directive. Active from July 1, 2006, the RoHS Directive 2002/95/EC adopted in February 2003 by the European Union, and adopted in Romania by HG - 992/2005, completed by HG - 816/2006, call forth important consequences in assembling technologies. In order to minimize manufacturing cost, Pin-In-Paste offers solutions for complete assembling of high complexity PCBs in Vapor Phase Technology using only one reflow machine avoiding overheating of the assemblies relatively to infrared reflow oven. Starting from RoHS consequences analysis, especially thermal profile, the paper presents the applied research performed in the assembling lines on VPS machine in order to define the design requirements for Pin-In-Paste dedicated stencils and PCBs, experiments result and conclusions regarding DFM requirements for lead-free assembling technologies of optoelectronic components. Finally, scientific and practical conclusions shall be drawn to configure the optimum implementation way for Pin-In-Paste in Vapor Phase Technology. The authors emphasizes that Vapor Phase Technology has all the conditions to become the disruptive technology of the moment.

Plotog, I.; Varzaru, G.; Turcu, C.; Cucu, T. C.; Svasta, P.; Vasile, A.

2009-01-01

231

Real-time trace detection of vapor-phase elemental mercury and its compounds  

NASA Astrophysics Data System (ADS)

The high toxicity of mercury species (elemental and compound) has prompted a demand for accurate, real-time inventory and control of their emissions. Our method of choice for mercury compound vapor is Photofragment Fluorescence spectroscopy. Target compound concentrations can be related to the fluorescence intensity from an excited fragment. Fragment identities and distributions, as revealed in the fluorescence spectrum provide information on the composition of the parent species. In the first experimental phase, a static cell (no flow) containing mercury compound (e.g. HgCl2 vapor was probed with a deep ultraviolet (UV) laser to generate characteristic spectra. An atmospheric pressure flow cell was used in the second stage. Limits-of-detection have been estimated. Detection schemes have included both photomultiplier tube (with interference filter) and charge- coupled-device camera (with monochromator). To reduce fluorescence quenching, we have expanded an argon gas stream containing Hg vapor through a micro-jet into a vacuum. The jet is crossed with a laser beam at 253.7 nm to excite atomic fluorescence, which is distinguished from the background by time gating.

Tong, Xiaomei; Barat, Robert B.; Poulos, Arthur T.

1999-12-01

232

Vapor-phase hydrogen peroxide as a surface decontaminant and sterilant.  

PubMed Central

The feasibility of utilizing vapor-phase hydrogen peroxide (VPHP) as a surface decontaminant and sterilant was evaluated in a centrifuge application. The prototype VPHP decontamination system, retrofitted into a Beckman L8-M ultracentrifuge, was designed to vaporize a 30% (wt/wt) solution of aqueous hydrogen peroxide continuously injecting and withdrawing VPHP in a deep-vacuum flow-through system. VPHP cycles of 4, 8, 16, and 32 min were examined for cidal activity against spores of Bacillus subtilis subsp. globigii and Bacillus stearothermophilus. Spore inocula (approximately 10(6)/coupon) were dried onto 0.5-in. (1.27-cm)-square stainless-steel coupons, and coupons were suspended in the centrifuge chamber, the space between the refrigeration can and the barrier ring (inner gap), and the space between the barrier ring and the vacuum ring (outer gap). At a chamber temperature of 4 degrees C, B. subtilis subsp. globigii spores were inactivated within 8 min, while inactivation of spores located in the outer gap at 27 degrees C required 32 min. The elevated temperature and high surface area/volume ratios in the outer gap may serve to decompose the gas more rapidly, thus reducing cidal efficacy. Of the two test spores, B. stearothermophilus was more resistant to VPHP. Nonetheless, VPHP was shown to possess significant sporicidal capability. For practical decontamination applications of the type described, VPHP shows promise as an effective and safer alternative to currently used ethylene oxide or formaldehyde vapors.

Klapes, N A; Vesley, D

1990-01-01

233

Liquid-Vapor Phase Extraction of Gasoline for In Situ Amelioration of Contaminated Clayey Soil  

NASA Astrophysics Data System (ADS)

Liquid-vapor phase extraction (LVPE) of hydrocarbon is a recognized technique for rapid remediation of gasoline contaminated soils and waters. On site application of LVPE is, however, challenging in clayey soils. Four LVPE events were conducted during a 10-month period at a central Californian site that had been contaminated with gasoline due to leakage of underground storage tanks. The site was underlain by unconsolidated alluvial deposits and the soil profile consisted of layers of sandy clays and silty clays with low water table. The objectives of this study were to reduce floating product volume in well waters and to remove petroleum hydrocarbons within the vadose zone. Groundwater was extracted by lowering a stinger to the groundwater surface and applying vacuum. The stingers were able to extract down to 20 ft below ground surface. Vacuum was applied at 25 in of Hg pressure and the LVPE unit extracted soil vapor at the rate of 54 ft3/min. Samples were collected periodically from the extracted groundwater, treated groundwater, extracted soil vapor, and analyzed for gasoline and its constituents. The LVPE showed a moderate impact on the floating product found beneath the site. The volumes of floating product, although measurable, were reduced significantly after the extraction operations. High hydrocarbon concentrations in soil vapor at initial period of extraction events suggested that hydrocarbon vaporization followed a rapid kinetics. During first couple of extraction events, this surge was a followed by a quick decline in concentrations over time. The vaporization process appeared to have reached steady state after repetitive extraction activities. The LVPE system extracted about 288-336 (x1000) liters of groundwater and 88-358 kg of hydrocarbons during the events. In subsequent monitoring studies, significant concentrations of gasoline and its constituents were detected in the well waters. This suggested that the residual contaminant pool could replenish the mobile hydrocarbon pool despite removal operations. The radius of influence of LVPE remained within 10 ft in both saturated and unsaturated zones due to the clayey soil structure. The overall mass of petroleum hydrocarbons remaining in the vadose zone around the wells appeared to have diminished.

Sharma, S.; Spencer, S.

2008-12-01

234

Vapor-phase addition of methanol to isobutene on a macroporous resin; A kinetic study  

SciTech Connect

The authors describe a study of the kinetics of the vapor-phase addition of methanol to isobutene to give methyl tert-butyl ether (MTBE) on the ion-exchange resin Amberlyst 15. Rate data were obtained in a continuous differential reactor operated at atmospheric pressure and 41-61.5{sup 0}C. The best-fitting Langmuir-Hinshelwood-Hougen-Watson (LHHW) rate equation is derived from a mechanism whose rate-determining step is the reaction between the methanol adsorbed molecularly on one center and the isobutene adsorbed on two centers. This mechanism is thermodynamically consistent.

Tejero, J.; Cunill, F.; Izquierdo, J.F. (Chemical Engineering Dept., Univ. of Barcelona, Marti i Franques 1, 08028 Barcelona (ES))

1989-09-01

235

Performance Testing of the Vapor Phase Catalytic Ammonia Removal Engineering Development Unit  

NASA Technical Reports Server (NTRS)

This paper describes the results of performance testing of the Vapor Phase Catalytic Ammonia Removal (VPCAR) technology. The VPCAR technology is currently being developed by NASA as a Mars transit vehicle water recycling system. NASA has recently completed-a grant-to develop a next generation VPCAR system. This grant concluded with the shipment of the final deliverable to NASA on 8/31/03. This paper presents the results of mass, power, volume, and acoustic measurements for the delivered system. Product water purity analysis for a Mars transit mission and a simulated planetary base wastewater ersatz are also provided.

Flynn, Michael; Tleimat, Maher; Nalette, Tim; Quinn, Gregory

2005-01-01

236

Synthesis of graphene nanoribbons from amyloid templates by gallium vapor-assisted solid-phase graphitization  

NASA Astrophysics Data System (ADS)

Single- and double-layer graphene nanoribbons (GNRs) with widths of around 10 nm were synthesized directly onto an insulating substrate by solid-phase graphitization using a gallium vapor catalyst and carbon templates made of amyloid fibrils. Subsequent investigation revealed that the crystallinity, conductivity, and carrier mobility were all improved by increasing the temperature of synthesis. The carrier mobility of the GNR synthesized at 1050 °C was 0.83 cm2/V s, which is lower than that of mechanically exfoliated graphene. This is considered to be most likely due to electron scattering by the defects and edges of the GNRs.

Murakami, Katsuhisa; Dong, Tianchen; Kajiwara, Yuya; Hiyama, Takaki; Takahashi, Teppei; Takai, Eisuke; Ohashi, Gai; Shiraki, Kentaro; Fujita, Jun-ichi

2014-06-01

237

Use of column V alkyls in organometallic vapor phase epitaxy (OMVPE)  

NASA Technical Reports Server (NTRS)

The use of the column V-trialkyls trimethylarsenic (TMAs) and trimethylantimony (TMSb) for the organometallic vapor phase epitaxy (OM-VPE) of III-V compound semiconductors is reviewed. A general discussion of the interaction chemistry of common Group III and Group V reactants is presented. The practical application of TMSb and TMAs for OM-VPE is demonstrated using the growth of GaSb, GaAs(1-y)Sb(y), Al(x)Ga(1-x)Sb, and Ga(1-x)In(x)As as examples.

Ludowise, M. J.; Cooper, C. B., III

1982-01-01

238

Vapor-phase bioreactors: Avoiding problems through better design and operation  

SciTech Connect

Vapor-phase bioreactors are an efficient method to treat air contaminated with volatile organic compounds. To ensure stable long term performance, several design and operating factors must be considered. Common problems include nutrient limitations, biomass clogging, inactive biomass, low moisture content and reductions in pH. Based on several bioreactor studies, the underlying cause of each of these problems is identified, monitoring requirements are outlined and a range of appropriate response actions are presented. These solutions range from modification of bioreactor design and operation (e.g., step feed configuration and directionally switching operation) to the use of alternative types of microorganisms (e.g., fungi).

Kinney, K.A.; Loehr, R.C.; Corsi, R.L.

1999-09-30

239

Metal organic vapor phase epitaxy of GaAsN/GaAs quantum wells using tertiarybutylhydrazine  

SciTech Connect

GaAsN epilayers and quantum wells with a good structural quality and surface morphology were grown by low pressure metal organic vapor phase epitaxy using tertiarybutylhydrazine as a novel nitrogen source. The dependence of nitrogen incorporation on growth temperature was studied for epitaxy with arsine and tertiarybutylarsine precursors. A nitrogen content of 6.7% was achieved using tertibarybutylhydrazine and tertiarybutylarsine at a low growth temperature of 530 C. The observed room temperature luminescence shows an increasing redshift with increasing nitrogen contents of the wells.

Schmidtling, T.; Klein, M.; Pohl, U.W.; Richter, W.

2000-07-01

240

Triboluminescence and Vapor-Induced Phase Transitions in the Solids of Methyltriphenylphosphonium Tetrahalomanganate(II) Complexes.  

PubMed

Triboluminescence (TL) of the methyltriphenylphosphonium tetrahalomanganate(II) complexes such as bis(methyltriphenylphosphonium) tetrabromomanganate (PMBB) and bis(methyltriphenylphosphonium) dibromodichloromanganate (PMBC) was switched ON and OFF reversibly by vapors of aprotic and protic solvents, respectively, for the first time. Detailed analyses indicate that solids of the PMBB and the PMBC undergo phase transitions depending on the environment, which regulate the TL activity of these compounds. The combined results of luminescence, powder X-ray diffraction, differential scanning calorimetry, and electron paramagnetic resonance were used to demonstrate crystal dynamism as well as the TL emission of PMBB and PMBC. PMID:24899549

Balsamy, Sujitha; Natarajan, Palani; Vedalakshmi, Rathinavel; Muralidharan, Srinivasan

2014-06-16

241

Liquid-Phase Compositions from Vapor-Phase Analyses. II. Adaptation of the Prausnitz Program to UF sub 6 and Some of Its Potential Impurities.  

National Technical Information Service (NTIS)

There is an economic incentive to use vapor-phase samples of UF sub 6 for determining the concentration of impurities in cylinders of UF sub 6 rather than using liquid-phase samples, as has been done in the past. Calculation of liquid-phase concentrations...

H. D. Cochran W. Davis

1985-01-01

242

Bubbles in liquids with phase transition. Part 1. On phase change of a single vapor bubble in liquid water  

NASA Astrophysics Data System (ADS)

In the forthcoming second part of this paper a system of balance laws for a multi-phase mixture with many dispersed bubbles in liquid is derived where phase transition is taken into account. The exchange terms for mass, momentum and energy explicitly depend on evolution laws for total mass, radius and temperature of single bubbles. Therefore in the current paper we consider a single bubble of vapor and inert gas surrounded by the corresponding liquid phase. The creation of bubbles, e.g. by nucleation is not taken into account. We study the behavior of this bubble due to condensation and evaporation at the interface. The aim is to find evolution laws for total mass, radius and temperature of the bubble, which should be as simple as possible but consider all relevant physical effects. Special attention is given to the effects of surface tension and heat production on the bubble dynamics as well as the propagation of acoustic elastic waves by including slight compressibility of the liquid phase. Separately we study the influence of the three phenomena heat conduction, elastic waves and phase transition on the evolution of the bubble. We find ordinary differential equations that describe the bubble dynamics. It turns out that the elastic waves in the liquid are of greatest importance to the dynamics of the bubble radius. The phase transition has a strong influence on the evolution of the temperature, in particular at the interface. Furthermore the phase transition leads to a drastic change of the water content in the bubble. It is shown that a rebounding bubble is only possible, if it contains in addition an inert gas. In Part 2 of the current paper the equations derived are sought in order to close the system of equations for multi-phase mixture balance laws for dispersed bubbles in liquids involving phase change.

Dreyer, Wolfgang; Duderstadt, Frank; Hantke, Maren; Warnecke, Gerald

2012-11-01

243

Cigars, Cigarettes, and Adolescents  

ERIC Educational Resources Information Center

Objective: To examine public health implications of adolescent use of cigars only, cigarettes only, and both cigarettes and cigars. Methods: A cross-sectional health risk survey was administered to a random sample of 4486 high school students in a Midwestern county. Results: More adolescents reported using both cigarettes and cigars (10.6%) than…

Brooks, Ashley; Larkin, Elizabeth M. Gaier; Kishore, Sonal; Frank, Scott

2008-01-01

244

Feasibility Study of Vapor-Mist Phase Reaction Lubrication Using a Thioether Liquid  

NASA Technical Reports Server (NTRS)

A primary technology barrier preventing the operation of gas turbine engines and aircraft gearboxes at higher temperatures is the inability of currently used liquid lubricants to survive at the desired operating conditions over an extended time period. Current state-of-the-art organic liquid lubricants rapidly degrade at temperatures above 300 C; hence, another form of lubrication is necessary. Vapor or mist phase reaction lubrication is a unique, alternative technology for high temperature lubrication. The majority of past studies have employed a liquid phosphate ester that was vaporized or misted, and delivered to bearings or gears where the phosphate ester reacted with the metal surfaces generating a solid lubricious film. This method resulted in acceptable operating temperatures suggesting some good lubrication properties, but the continuous reaction between the phosphate ester and the iron surfaces led to wear rates unacceptable for gas turbine engine or aircraft gearbox applications. In this study, an alternative non-phosphate liquid was used to mist phase lubricate a spur gearbox rig operating at 10,000 rpm under highly loaded conditions. After 21 million shaft revolutions of operation the gears exhibited only minor wear.

Morales, Wilfredo; Handschuh, Robert F.; Krantz, Timothy L.

2007-01-01

245

Mechanistic investigation of non-ideal sorption behavior in natural organic matter. 1. Vapor phase equilibrium.  

PubMed

Results from an experimental and modeling investigation of the influence of thermodynamic properties of highly purified natural organic matter (NOM) on observed equilibrium sorption/desorption behaviors of vapor phase trichloroethylene (TCE) is presented. Identification of glass transition (T(g)) behavior in Leonardite humic acid and Organosolv lignin enabled evaluation of equilibrium and nonequilibrium sorption behavior in glassy and rubbery NOM. Specific differences in vapor phase equilibrium behavior in NOM above and below their T(g) were identified. In the glassy state (below T(g)), sorption of TCE is well-described by micropore models, with enthalpies of sorption characteristic of microporous, glassy macromolecules. Above T(g), sorptive behavior was well-described by Flory-Huggins theory, indicating that the mobility and structural configuration of rubbery NOM materials may be analogous to the characteristic sorption behavior observed in more mobile, rubbery macromolecules, including strong entropic changes during sorption. Results from this work provide further support that, at least for the samples employed in this study, NOM possesses macromolecular characteristics which display sorption behavior similar to synthetic macromolecules-an important assumption in conceptual sorption equilibrium models used in the analysis of the fate and transport of VOCs in the environment. PMID:22642948

Bell, Katherine Young; Leboeuf, Eugene J

2012-06-19

246

Reaction of methane with vapor-phase transition-metal chlorides  

SciTech Connect

Chemical processing of raw materials with the natural gas, methane, is under study to see if it can replace the gases normally used. Interest in the reaction of methane with transition-metal chlorides in the vapor phase is due to the following factors. First, methane as a reducing agent can replace hydrogen, widely used for reducing metal chlorides, to yield ultrapure metals. Second, metal chlorides are of interest as catalysts for methane chlorination with subsequent conversion to ethylene or aromatic hydrocarbons. The latter two-step method of obtaining organics from methane is industrially simpler than by direct conversion of methane into ethylene by the Benson method. Chlorinated methanes are obtained by heating methane with molecular chlorine. This reaction is the basis of industrial chlorinated methane production but has a number of problems that prompt searching for catalytic chlorinations. The present paper presents a more detailed study of methane chlorination in the presence of MoCl{sub 5}, WCl{sub 6} and correlates the results with the reaction of methane with other vapor-phase transition-metal chlorides. 12 refs., 3 figs., 1 tab.

Didenko, L.P.; Chekh, N.A.; Shiryaev, A.A.; Savchenko, V.I.

1992-07-10

247

Uptake rate constants and partition coefficients for vapor phase organic chemicals using semipermeable membrane devices (SPMDs)  

USGS Publications Warehouse

To fully utilize semipermeable membrane devices (SPMDs) as passive samplers in air monitoring, data are required to accurately estimate airborne concentrations of environmental contaminants. Limited uptake rate constants (kua) and no SPMD air partitioning coefficient (Ksa) existed for vapor-phase contaminants. This research was conducted to expand the existing body of kinetic data for SPMD air sampling by determining kua and Ksa for a number of airborne contaminants including the chemical classes: polycyclic aromatic hydrocarbons, organochlorine pesticides, brominated diphenyl ethers, phthalate esters, synthetic pyrethroids, and organophosphate/organosulfur pesticides. The kuas were obtained for 48 of 50 chemicals investigated and ranged from 0.03 to 3.07??m3??g-1??d-1. In cases where uptake was approaching equilibrium, Ksas were approximated. Ksa values (no units) were determined or estimated for 48 of the chemicals investigated and ranging from 3.84E+5 to 7.34E+7. This research utilized a test system (United States Patent 6,877,724 B1) which afforded the capability to generate and maintain constant concentrations of vapor-phase chemical mixtures. The test system and experimental design employed gave reproducible results during experimental runs spanning more than two years. This reproducibility was shown by obtaining mean kua values (n??=??3) of anthracene and p,p???-DDE at 0.96 and 1.57??m3??g-1??d-1 with relative standard deviations of 8.4% and 8.6% respectively.

Cranor, W. L.; Alvarez, D. A.; Huckins, J. N.; Petty, J. D.

2009-01-01

248

Reaction mechanisms in the organometallic vapor phase epitaxial growth of GaAs  

NASA Technical Reports Server (NTRS)

The decomposition mechanisms of AsH3, trimethylgallium (TMGa), and mixtures of the two have been studied in an atmospheric-pressure flow system with the use of D2 to label the reaction products which are analyzed in a time-of-flight mass spectrometer. AsH3 decomposes entirely heterogeneously to give H2. TMGa decomposes by a series of gas-phase steps, involving methyl radicals and D atoms to produce CH3D, CH4, C2H6, and HD. TMGa decomposition is accelerated by the presence of AsH3. When the two are mixed, as in the organometallic vapor phase epitaxial growth of GaAs, both compounds decompose in concert to produce only CH4. A likely model is that of a Lewis acid-base adduct that forms and subsequently eliminates CH4.

Larsen, C. A.; Buchan, N. I.; Stringfellow, G. B.

1988-01-01

249

He II Liquid/Vapor Phase Separator for Large Dynamic Range Operation  

NASA Technical Reports Server (NTRS)

A phase separator, which separates helium vapor from liquid superfluid helium (He II), is an indispensable device for space cryogenics. The most recent approach to the Space Infrared Telescope Facility (SIRTF) uses a new design concept in which only the detector package is cold at launch, the remainder of the telescope being subsequently cooled to operating temperature on orbit. Therefore, a large dynamic operational range is required of the cryogen system. This is a report of initial laboratory test results with candidate porous plugs as phase separators. Mass flow rates and pressure and temperature differences across a porous plug were measured in this experiment. Relatively large mass flow rates were observed even at small pressure differences. In the high mass flow rate region, a hysteresis was observed with increases and decreases of the pressure difference. A linear theory is proposed and compared with experimental data to explain several phenomena observed in this system.

Nakano, A.; Petrac, D.

1995-01-01

250

Wettability alteration of model sandstone surfaces by vapor-phase treatment with organosilanes  

SciTech Connect

The wettability of a rock-fluid system has a major influence on the amount of residual oil in a reservoir and its ease of recovery. We have investigated a technique for modifying the natural water-wetness of clean, dry mineral samples by chemically incorporating organosilanes onto their surfaces (silylation). The goal is to provide simulated core samples with different degrees of wettability. Data from wettability measurements on these model cores could then be compared to that obtained on actual reservoir core samples. Discussion will specifically focus on: (1) comparison of quartz plates silylated by our vapor-phase technique vs. a solvent-phase treatment; (2) relative performance of two different types of organosilanes; and (3) effect of temperature.

Takach, N.E.; Bennett, L.B.; Douglas, C.B.; Andersen, M.A.; Thomas, D.C.

1988-08-01

251

Measurements of quantum noise in optical phase conjugation via four-wave mixing in an atomic vapor  

Microsoft Academic Search

We present the results of a comprehensive investigation of the quantum-noise properties of a continuous- wave phase-conjugate mirror ~PCM! formed using backward-four-wave mixing in potassium vapor. We char- acterize the quantum-noise properties of the PCM as functions of the vapor density, pump detuning from resonance, and relative frequency detuning of the signal beam from the probe beam. We compare the

M. Y. Lanzerotti; R. W. Schirmer; Alexander L. Gaeta

1999-01-01

252

Measurements of quantum noise in optical phase conjugation via four-wave mixing in an atomic vapor  

Microsoft Academic Search

We present the results of a comprehensive investigation of the quantum-noise properties of a continuous-wave phase-conjugate mirror (PCM) formed using backward-four-wave mixing in potassium vapor. We characterize the quantum-noise properties of the PCM as functions of the vapor density, pump detuning from resonance, and relative frequency detuning of the signal beam from the probe beam. We compare the noise measurements

M. Y. Lanzerotti; R. W. Schirmer; Alexander L. Gaeta; G. S. Agarwal

1999-01-01

253

Vapor-phase sorption of hexachlorobenzene on typical municipal solid waste (MSW) incineration fly ashes, clay minerals and activated carbon  

Microsoft Academic Search

Column sorption experiments were conducted at 330°C and 250°C to study the vapor-phase sorption of hexachlorobenzene (HCB) on two kinds of municipal solid waste (MSW) incinerator fly ashes, kaolinite, montmorillonite and activated carbon (AC). Both Freundlich equation and linear equation well fitted the sorption isotherms of HCB vapor on fly ashes and clay minerals at 330°C (r2>0.87), while the sorption

Yuan Gao; Haijun Zhang; Jiping Chen

2010-01-01

254

Vapor pressures and gas-phase PVT data for 1-Chloro-1,2,2,2-tetrafluoroethane (R124)  

Microsoft Academic Search

We present new data for the vapor pressure andPVT surface of 1-chloro-1,2,2,2-lelralluoroethane (designated R124 by the refrigeration industry) in the temperature range 278–423 K. ThePVT data are for the gas phase at densities up to 1.5 times the critical density. Correlating equations are given for the vapor pressures from 220 K to the critical temperature, 395.43 K, and for thePVT

S. J. Boyes; L. A. Weber

1994-01-01

255

Stimulated topological condensation of ``vapor phase'' photons and possible implications for space power technology  

NASA Astrophysics Data System (ADS)

A quantum topological network model that might allow for the production of energy through the employment of vacuum electromagnetic currents form is based upon foundational principles of topological geometrodynamics (TGD) (Pitkänen, 1995a, 1995b). Such a production photon-factory would have the capability of drawing upon a seemingly inexhaustible supply of what in TGD formalism is a ``vapor phase'' of photons. Particularly in the presence of Bose-Einstein condensate photons, it is theoretically possible to convert these ``vapor phase'' photons into condensed photons that can then be harnessed and transformed into useful kinetic energy by more traditional means. TGD presents a view, similar to certain string models, of spacetimes as surfaces within an 8-dimensional space H that is a product of Minkowski space future lightcone M+4 and a complex projective space CP2. TGD model allows for topological merging, akin to the condensation process in classical physics, of free elementary particle like 3-surfaces to the background surface of larger size. ``Topological evaporation'' corresponds to the reverse of this process in which particles go ``outside'' the classical spacetime. TGD predicts vacuum electromagnetic fields having as their source vacuum gauge currents instead of currents composed of elementary particles. The vacuum gauge currents generate coherent states of photons and for the lightlike vacuum currents the coherent state arises in a resonant-like manner. A presence of Bose-Einstein condensates of photons in a nearby spacetime sheet external to the coherent-state generator would allow for a transfer of photons from that sheet into a vapor phase. The capture of these photons into an electro-mechanical propulsion system may provide a source of energy which can be converted into a form useful for the propulsion and acceleration of a space craft. An emission of coherent light from a region not containing charged particles would be a clear indication of vacuum current presence. Whether this entire process, if it is feasible, could generate enough useful energy for spacecraft propulsion is a major open question. However, it does appear that in the least such a mechanism could provide for some type of quantum communication with storage of information in both phase and intensity of the coherent emf and with the vacuum currents acting as quantum antennae. An examination of certain models known as quantum cellular automata and networks (QCAM, CLAN) (Dudziak, 1993) and synchronized heterogeneous dynamical networks (SHDN) (Chinarov, 1998) may provide some further insight into how the suggested stimulated coherent production of photons might be initiated, controlled, and stabilized in an application for space travel or communication.

Dudziak, M.; Pitkänen, M.

1999-01-01

256

Cigarette filter as sorbent for on-line coupling of solid-phase extraction to high-performance liquid chromatography for determination of polycyclic aromatic hydrocarbons in water.  

PubMed

An on-line solid-phase extraction (SPE) protocol using the cigarette filter as sorbent coupled with high-performance liquid chromatography (HPLC) was developed for simultaneous determination of trace naphthalene (NAPH), phenanthrene (PHEN), anthracene (ANT), fluoranthene (FLU), benzo(b)fluoranthene (BbF), benzo(k)fluoranthene (BkF), benzo(a)pyrene (BaP), and benzo(ghi)perylene (BghiP) in water samples. To on-line interface solid-phase extraction to HPLC, a preconcentration column packed with the cigarette filter was used to replace a conventional sample loop on the injector valve of the HPLC for on-line solid-phase extraction. The sample solution was loaded and the analytes were then preconcentrated onto the preconcentration column. The collected analytes were subsequently eluted with a mobile phase of methanol-water (95:5). HPLC with a photodiode array detector was used for their separation and detection. The detection limits (S/N = 3) for preconcentrating 42 mL of sample solution ranged from 0.9 to 58.6 ng L(-1) at a sample throughput of 2 samples h(-1). The enhancement factors were in the range of 409-1710. The developed method was applied to the determination of trace NAPH, PHEN, ANT, FLU, BbF, BkF, BaP and BghiP in local river water samples. The recoveries of PAHs spiked in real water samples ranged from 87 to 115%. The precisions for nine replicate measurements of a standard mixture (NAPH: 4.0 microg L(-1), PHEN: 0.40 microg L(-1), ANT: 0.40 microg L(-1), FLU: 2.0 microg L(-1), BbF: 1.6 microg L(-1), BkF: 2.0 microg L(-1), BaP: 2.0 microg L(-1), BghiP: 1.7 microg L(-1)) were in the range of 1.2-5.1%. PMID:16310206

Liang, Hua-Ding; Han, De-Man; Yan, Xiu-Ping

2006-01-20

257

In Vivo Versus In Vitro Airway Surface Liquid Nicotine Levels Following Cigarette Smoke Exposure  

PubMed Central

Whole cigarette smoke (WCS) is composed of approximately 5% particulates and 95% vapors by weight and is difficult to reproduce quantitatively in the laboratory, where typically, routine in vitro application of smoke normally only utilizes the particulate phase. In this study, we used a system for exposing epithelial cells cultured at an air-liquid interface to WCS. We hypothesized that the use of WSC in vitro was more relevant to what is seen in vivo than methods of cigarette smoke application that only use a small fraction of WCS [i.e., aqueous extract or cigarette smoke condensate (CSC)]. To test this hypothesis, we compared nicotine and cotinine concentrations (measured by mass spectrometry) in the airway surface liquid (ASL) of human primary bronchial epithelial cultures (HBECs) exposed to serial dilutions of WCS to the concentrations found in induced sputum of human subjects who had recently smoked a cigarette; this was also compared to the concentrations found after an exposure to a concentration of CSC commonly used in vitro. When measured by mass spectrometry, nicotine levels were not significantly different in induced sputum versus the ASL of HBECs exposed in vitro to a 1:30 exposure of WCS. However, HBECs that had been exposed to CSC returned significantly lower concentrations of ASL nicotine. These results suggest that nicotine is a good dosimetry marker of WCS exposure and provides direct evidence that the use of WCS is more relevant than the use of CSC for in vitro systems.

Clunes, Lucy A.; Bridges, Arlene; Alexis, Neil; Tarran, Robert

2010-01-01

258

Triple sorbent thermal desorption/gas chromatography/mass spectrometry determination of vapor phase organic contaminants  

SciTech Connect

A thermal desorption/ps chromatography/mass spectrometry (TD/GC/MS) has been evaluated for the determination of volatile organic compounds (VOCS) in vapor phase samples using Carbosieve S-III/Carbotrap/Carotrap C triple sorbent traps (TST) similar to those available from a commercial source. The analysis was carried out with a Hewlett-Packard 5985A or 5995 GC/MS system with a modified injector to adapt an inhouse manufactured short-path desorber for transferring desorbate directly onto a cryofocusing loop for subsequent GC/MS analysis. Vapor phase standards generated from twenty six compounds were used for method validation, including alkanes, alkyl alcohols, alkyl ketones, and alkyl nitrites, a group of representative compounds that have previously been identified in a target airborne matrix. The method was validated based on the satisfactory results in terms of reproducibility, recovery rate, stability, and linearity. A relative, standard deviation of 0.55 to 24.3 % was obtained for the entire TD process (generation of gas phase standards, spiking the standards on and desorbing from TST) over a concentration range of 20 to 500 ng/trap. Linear correlation coefficients for the calibration curves as determined ranged from 0.81 to 0.99 and limits of detection ranged from 3 to 76 ng. For a majority of standards, recoveries of greater than 90% were observed. For three selected standards spiked on TSTS, minimal loss (10 to 22%) was observed after storing the spiked in, a 4{degree}C refrigerator for 29 days. The only chromatographable artifact observed was a 5% conversion of isopropanol to acetone. The validated method been successfully applied, to the determination of VOCs collected from various emission sources in a diversified concentration range.

Ma, C.Y.; Skeen, J.T.; Dindal, A.B.; Higgins, C.E.; Jenkins, R.A.

1994-05-01

259

Evaluating the robustness of the enantioselective stationary phases on the Rosetta mission against space vacuum vaporization  

NASA Astrophysics Data System (ADS)

The European Space Agency's Rosetta mission was launched in March 2004 in order to reach comet 67P/Churyumov-Gerasimenko by August 2014. The Cometary Sampling and Composition experiment (COSAC) onboard the Rosetta mission's lander "Philae" has been designed for the cometary in situ detection and quantification of organic molecules using gas chromatography coupled to mass spectrometry (GC-MS). The GC unit of COSAC is equipped with eight capillary columns that will each provide a specific stationary phase for molecular separation. Three of these stationary phases will be used to chromatographically resolve enantiomers, as they are composed of liquid polymers of polydimethylsiloxane (PDMS) to which chiral valine or cyclodextrin units are attached. Throughout the ten years of Rosetta's journey through space to reach comet 67P, these liquid stationary phases have been exposed to space vacuum, as the capillary columns within the COSAC unit were not sealed or filled with carrier gas. Long term exposures to space vacuum can cause damage to such liquid stationary phases as key monomers, volatiles, and chiral selectors can be vaporized and lost in transit. We have therefore exposed identical spare units of COSAC's chiral stationary phases over eight years to vacuum conditions mimicking those experienced in space and we have now investigated their resolution capabilities towards different enantiomers both before and after exposure to space vacuum environments. We have observed that enantiomeric resolution capabilities of these chiral liquid enantioselective stationary phases has not been affected by exposure to space vacuum conditions. Thus we conclude that the three chiral stationary phases of the COSAC experiment onboard the Rosetta mission lander "Philae" can be considered to have maintained their resolution capacities throughout their journey prior to cometary landing in November 2014.

Meierhenrich, Uwe J.; Cason, Julie R. L.; Szopa, Cyril; Sternberg, Robert; Raulin, François; Thiemann, Wolfram H.-P.; Goesmann, Fred

2013-12-01

260

Effectiveness of cigarette filter tips for reducing cadmium in relation to other mainstream smoke constituents  

SciTech Connect

The effectiveness of filter tips for reducing cadmium, tar, nicotine, carbon monoxide and carbon dioxide in cigarettes was studied. The cigarettes were made from tobacco grown on municipal sewage sludge-amended soil and were therefore high in cadmium. When machine-smoked, filter tips did not result in a significant reduction of cadmium deposited on Cambridge filters. This may indicate that a considerable fraction of cadmium is present in the vapor phase of the smoke and therefore not reduced to the same extent as the tar by certain filters. Nicotine and carbon monoxide were reduced to a lesser extent than tar. This indicates that the filter tip has influenced the combustion of the tobacco column during smoking.

Bache, C.A.; Lisk, D.J.; Shane, B.S.; Hoffmann, D.; Adams, J.D.

1987-01-01

261

Tank vapor sampling and analysis data package for tank 241-C-106 waste retrieval sluicing system process test phase III  

SciTech Connect

This data package presents sampling data and analytical results from the March 28, 1999, vapor sampling of Hanford Site single-shell tank 241-C-106 during active sluicing. Samples were obtained from the 296-C-006 ventilation system stack and ambient air at several locations. Characterization Project Operations (CPO) was responsible for the collection of all SUMMATM canister samples. The Special Analytical Support (SAS) vapor team was responsible for the collection of all triple sorbent trap (TST), sorbent tube train (STT), polyurethane foam (PUF), and particulate filter samples collected at the 296-C-006 stack. The SAS vapor team used the non-electrical vapor sampling (NEVS) system to collect samples of the air, gases, and vapors from the 296-C-006 stack. The SAS vapor team collected and analyzed these samples for Lockheed Martin Hanford Corporation (LMHC) and Tank Waste Remediation System (TWRS) in accordance with the sampling and analytical requirements specified in the Waste Retrieval Sluicing System Vapor Sampling and Analysis Plan (SAP) for Evaluation of Organic Emissions, Process Test Phase III, HNF-4212, Rev. 0-A, (LMHC, 1999). All samples were stored in a secured Radioactive Materials Area (RMA) until the samples were radiologically released and received by SAS for analysis. The Waste Sampling and Characterization Facility (WSCF) performed the radiological analyses. The samples were received on April 5, 1999.

LOCKREM, L.L.

1999-08-13

262

Distribution of density fluctuations in a molecular theory of vapor-phase nucleation  

NASA Astrophysics Data System (ADS)

A statistical-mechanical theory of the distribution of density fluctuations involved in homogeneous vapor-phase nucleation is presented which improves on previous work. Specifically, a refined characterization of a physical cluster is developed. This cluster is known as an i/v cluster, since it is defined by both a molecular number i and a volume v (i/v is the average density of molecules in the cluster). The i/v cluster represents the density fluctuations that have the potential to serve as condensation centers for the formation of liquid drops. The refinement involves a so-called shell molecule which defines the volume v. The equilibrium distribution of the refined i/v clusters is derived, using an approach involving fluctuation theory. This method is as rigorous as prior approaches and, moreover, sheds light on the nature of the cluster distribution and the cluster itself. Through an analysis of a cluster defined without a shell molecule, it is shown that the shell molecule is necessary if the cluster characterization is to be consistent with the fundamental statistical-mechanical description of the supersaturated vapor. Finally, as a by-product of this work, it is shown that the awkwardness of the constant-pressure ensemble associated with its expression as a sum over volume is automatically removed once the necessary presence of a shell molecule is recognized.

Ellerby, H. Michael

1994-05-01

263

ZnO Nanowires Synthesized by Vapor Phase Transport Deposition on Transparent Oxide Substrates  

PubMed Central

Zinc oxide nanowires have been synthesized without using metal catalyst seed layers on fluorine-doped tin oxide (FTO) substrates by a modified vapor phase transport deposition process using a double-tube reactor. The unique reactor configuration creates a Zn-rich vapor environment that facilitates formation and growth of zinc oxide nanoparticles and wires (20–80 nm in diameter, up to 6 ?m in length, density <40 nm apart) at substrate temperatures down to 300°C. Electron microscopy and other characterization techniques show nanowires with distinct morphologies when grown under different conditions. The effect of reaction parameters including reaction time, temperature, and carrier gas flow rate on the size, morphology, crystalline structure, and density of ZnO nanowires has been investigated. The nanowires grown by this method have a diameter, length, and density appropriate for use in fabricating hybrid polymer/metal oxide nanostructure solar cells. For example, it is preferable to have nanowires no more than 40 nm apart to minimize exciton recombination in polymer solar cells.

2010-01-01

264

Vapor-phase sorption of hexachlorobenzene on typical municipal solid waste (MSW) incineration fly ashes, clay minerals and activated carbon.  

PubMed

Column sorption experiments were conducted at 330°C and 250°C to study the vapor-phase sorption of hexachlorobenzene (HCB) on two kinds of municipal solid waste (MSW) incinerator fly ashes, kaolinite, montmorillonite and activated carbon (AC). Both Freundlich equation and linear equation well fitted the sorption isotherms of HCB vapor on fly ashes and clay minerals at 330°C (r(2)>0.87), while the sorption isotherm of HCB vapor on AC at 330°C was in the shape of Brunauer type-II adsorption. Catalytic dechlorination of HCB was found to occur on the surface of fly ashes, and pentachlorobenzene was the only dechlorination product detected in the effluent gas. Increasing temperature decreased the sorption of HCB vapor on fly ashes, and promoted the catalytic dechlorination of HCB. On the assumption that the organic carbon and clay minerals in fly ash were derived from AC, kaolinite and montmorillonite, the relative contributions of these components to the apparent sorption capacity of fly ashes at 330°C were estimated. It was found that very small percentage of AC contributed the most to the apparent sorption of HCB vapor on fly ash. The sorption coefficient of HCB on montmorillonite at 250°C was 37 times higher than that at 330°C, suggesting montmorillonite could be a kind of low-cost sorbent to effectively reduce the emission of vapor-phase organochlorine compounds from MSW incinerators. PMID:20875668

Gao, Yuan; Zhang, Haijun; Chen, Jiping

2010-11-01

265

A three-dimensional phase field model for nanowire growth by the vapor–liquid–solid mechanism  

NASA Astrophysics Data System (ADS)

We present a three-dimensional multi-phase field model for catalyzed nanowire (NW) growth by the vapor–liquid–solid (VLS) mechanism. The equation of motion contains both a Ginzburg–Landau term for deposition and a diffusion (Cahn–Hilliard) term for interface relaxation without deposition. Direct deposition from vapor to solid, which competes with NW crystal growth through the molten catalyst droplet, is suppressed by assigning a very small kinetic coefficient at the solid–vapor interface. The thermodynamic self-consistency of the model is demonstrated by its ability to reproduce the equilibrium contact angles at the VLS junction. The incorporation of orientation dependent gradient energy leads to faceting of the solid–liquid and solid–vapor interfaces. The model successfully captures the curved shape of the NW base and the Gibbs–Thomson effect on growth velocity.

Wang, Yanming; Ryu, Seunghwa; McIntyre, Paul C.; Cai, Wei

2014-07-01

266

Reduction of degradation in vapor phase transported InP/InGaAsP mushroom stripe lasers  

SciTech Connect

The rapid degradation rate generally observed in InP/InGaAsP mushroom stripe lasers can be considerably decreased by regrowing the open sidewalls of the active stripe with low-doped InP in a second epitaxial step using the hydride vapor phase transport technique. This technique does not change the fundamental laser parameters like light-current and current-voltage characteristics. Because of this drastic reduction in degradation, the vapor phase epitaxy regrown InP/InGaAsP mushroom laser seems to be an interesting candidate for application in optical communication.

Jung, H.; Burkhardt, E.G.; Pfister, W.

1988-10-03

267

Cigarette filters as adsorbents of solid-phase extraction for determination of fluoroquinolone antibiotics in environmental water samples coupled with high-performance liquid chromatography.  

PubMed

The potential use of cigarette filters (CFs) as solid-phase extraction (SPE) adsorbents for the preconcentration of six fluoroquinolones (FQs) antibacterial agents prior to liquid chromatography was examined in this paper. In order to find a suitable procedure for extraction of the target FQs in one single step, various parameters probably affecting the extraction efficiency including the eluent kind and volume, sample flow rate, pH, ion strength and sample volume were systematically optimized. Under the optimized conditions, the target FQs could be easily extracted by the proposed SPE cartridge. Combination of SPE with HPLC/UV provided detection limits for different FQs of 2-5 ng L(-1) when 500 mL of water sample was processed. The precision of the method, expressed as relative standard deviation, ranged from 4.1 to 6.3% for 2.5 ?g L(-1) FQs. The recoveries of FQs spiked in environmental water samples ranged from 76 to 112%. The results obtained from the proposed method demonstrated that CFs-based solid-phase extraction combined with HPLC/UV was suitable for analyzing fluoroquinolones in water samples at ng L(-1) concentration level. PMID:22265493

Chen, Bo; Wang, Weidong; Huang, Yuming

2012-01-15

268

Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling.  

PubMed

The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 ?m were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%. PMID:21711730

Peng, Hao; Ding, Guoliang; Hu, Haitao

2011-01-01

269

Migration of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling  

PubMed Central

The migration characteristics of carbon nanotubes from liquid phase to vapor phase in the refrigerant-based nanofluid pool boiling were investigated experimentally. Four types of carbon nanotubes with the outside diameters from 15 to 80 nm and the lengths from 1.5 to 10 ?m were used in the experiments. The refrigerants include R113, R141b and n-pentane. The oil concentration is from 0 to 10 wt.%, the heat flux is from 10 to 100 kW·m-2, and the initial liquid-level height is from 1.3 to 3.4 cm. The experimental results indicate that the migration ratio of carbon nanotube increases with the increase of the outside diameter or the length of carbon nanotube. For the fixed type of carbon nanotube, the migration ratio decreases with the increase of the oil concentration or the heat flux, and increases with the increase of the initial liquid-level height. The migration ratio of carbon nanotube increases with the decrease of dynamic viscosity of refrigerant or the increase of liquid phase density of refrigerant. A model for predicting the migration ratio of carbon nanotubes in the refrigerant-based nanofluid pool boiling is proposed, and the predictions agree with 92% of the experimental data within a deviation of ±20%.

2011-01-01

270

High-resolution discrete absorption spectrum of ?-methallyl free radical in the vapor phase  

NASA Astrophysics Data System (ADS)

The ?-methallyl free radical is formed in the flash photolysis of 3-methylbut-1-ene, and cis-pent-2-ene in the vapor phase, and then subsequent reactions have been investigated by kinetic spectroscopy and gas-liquid chromatography. The photolysis flash was of short duration and it was possible to follow the kinetics of the radicals' decay, which occurred predominantly by bimolecular recombination. The measured rate constant for the ?-methallyl recombination was (3.5 ± 0.3) × 10 10 mol -1 l s -1 at 295 ± 2 K. The absolute extinction coefficients of the ?-methallyl radical are calculated from the optical densities of the absorption bands. Detailed analysis of related absorption bands and lifetime measurements in the original ?-methallyl high-resolution discrete absorption spectrum image were also carried out by image processing techniques.

Bayrakçeken, Fuat; Telatar, Ziya; Ar?, Fikret; Tunçyürek, Lale; Karaaslan, ?pek; Yaman, Ali

2006-09-01

271

Accumulation of Background Impurities in Hydride Vapor Phase Epitaxy Grown GaN Layers  

NASA Astrophysics Data System (ADS)

We report on accumulation of background Si and O impurities measured by secondary ion mass spectrometry (SIMS) at the sub-interfaces in undoped, Zn- and Mg-doped multi-layer GaN structures grown by hydride vapor phase epitaxy (HVPE) on sapphire substrates with growth interruptions. The impurities accumulation is attributed to reaction of ammonia with the rector quartz ware during the growth interruptions. Because of this effect, HVPE-grown GaN layers had excessive Si and O concentration on the surface that may hamper forming of ohmic contacts especially in the case of p-type layers and may complicate homo-epitaxial growth of a device structure.

Usikov, Alexander; Soukhoveev, Vitali; Kovalenkov, Oleg; Syrkin, Alexander; Shapovalov, Liza; Volkova, Anna; Ivantsov, Vladimir

2013-08-01

272

On the chloride vapor-phase epitaxy growth of GaN and its characterization  

NASA Astrophysics Data System (ADS)

In this article, we present details on the fabrication of the chloride vapor-phase epitaxy (Cl-VPE) system for the growth of gallium nitride (GaN). Growth of GaN on (0 0 0 1) sapphire substrates has been carried out at different growth temperatures while keeping the flow rate of the carrier gas as a constant. The crystalline and optical qualities of GaN grown layers by Cl-VPE were evaluated as a function of the growth temperature. An X-ray diffractometer and Raman scattering studies are used to determine the structural properties of the film. The optical properties are evaluated using a UV-absorption spectrometer and photoluminescence studies at room temperature. The quality of the films grown at different temperatures is compared. The optimum conditions to realize good crystal structure and smoother surface morphology have been obtained and reported.

Varadarajan, E.; Puviarasu, P.; Kumar, J.; Dhanasekaran, R.

2004-01-01

273

An Assessment of the Technical Readiness of the Vapor Phase Catalytic Ammonia Removal Process (VPCAR) Technology  

NASA Technical Reports Server (NTRS)

This poster provides an assessment of the technical readiness of the Vapor Phase Catalytic Ammonia Removal Process (VPCAR). The VPCAR technology is a fully regenerative water recycling technology designed specifically for applications such as a near term Mars exploration mission. The VPCAR technology is a highly integrated distillation/catalytic oxidation based water processor. It is designed to accept a combined wastewater stream (urine, condensate, and hygiene) and produces potable water in a single process step which requires -no regularly scheduled re-supply or maintenance for a 3 year mission. The technology is designed to be modular and to fit into a volume comparable to a single International Space Station Rack (when sized for a crew of 6). This poster provides a description of the VPCAR technology and a summary of the current performance of the technology. Also provided are the results of two separate NASA sponsored system trade studies which investigated the potential payback of further development of the VPCAR technology.

Flynn, Michael

2000-01-01

274

Hydride vapor phase epitaxy-grown AlGaN/GaN high electron mobility transistors  

NASA Astrophysics Data System (ADS)

High quality undoped AlGaN/GaN high electron mobility transistors (HEMTs) structures have been grown by hydride vapor phase epitaxy (HVPE), for the first time. The morphology of the films grown on Al 2O 3 substrates is excellent, with a root-mean-square roughness of ˜0.2 nm over 10×10 ?m 2 measurement area. Capacitance-voltage measurements show the formation of a dense sheet of charge at the AlGaN/GaN interface. This is the first ever report of the formation of a two-dimensional electron gas in a nitride structure grown by HVPE. HEMTs with 1 ?m gate length fabricated on these structures show transconductances in excess of 110 mS/mm and drain-source current above 0.6 A/mm.

Mastro, M. A.; Tsvetkov, D.; Soukhoveev, V.; Usikov, A.; Dmitriev, V.; Luo, B.; Ren, F.; Baik, K. H.; Pearton, S. J.

2003-06-01

275

Heterojunction Hybrid Devices from Vapor Phase Grown MoS2.  

PubMed

We investigate a vertically-stacked hybrid photodiode consisting of a thin n-type molybdenum disulfide (MoS2) layer transferred onto p-type silicon. The fabrication is scalable as the MoS2 is grown by a controlled and tunable vapor phase sulfurization process. The obtained large-scale p-n heterojunction diodes exhibit notable photoconductivity which can be tuned by modifying the thickness of the MoS2 layer. The diodes have a broad spectral response due to direct and indirect band transitions of the nanoscale MoS2. Further, we observe a blue-shift of the spectral response into the visible range. The results are a significant step towards scalable fabrication of vertical devices from two-dimensional materials and constitute a new paradigm for materials engineering. PMID:24975741

Yim, Chanyoung; O'Brien, Maria; McEvoy, Niall; Riazimehr, Sarah; Schäfer-Eberwein, Heiko; Bablich, Andreas; Pawar, Ravinder; Iannaccone, Giuseppe; Downing, Clive; Fiori, Gianluca; Lemme, Max C; Duesberg, Georg S

2014-01-01

276

Si Doping of GaN in Hydride Vapor-Phase Epitaxy  

NASA Astrophysics Data System (ADS)

Growth of GaN boules by hydride vapor-phase epitaxy (HVPE) is very attractive for fabrication of GaN substrates. Use of dichlorosilane as a source for Si doping of bulk GaN is investigated. It is shown that no tensile strain is incorporated into mm-thick, Si-doped GaN layers on sapphire substrates if the threading dislocation density is previously reduced to 2.5 × 107 cm-2 or below. High-quality GaN layers with electron densities up to 1.5 × 1019 cm-3 have been achieved, and an upper limit of about 4 × 1019 cm-3 for Si doping of GaN boules was deduced considering the evolution of dislocations with thickness. A 2-inch, Si-doped GaN crystal with length exceeding 6 mm and targeted Si doping of about 1 × 1018 cm-3 is demonstrated.

Richter, E.; Stoica, T.; Zeimer, U.; Netzel, C.; Weyers, M.; Tränkle, G.

2013-05-01

277

Uniform deposition of GaAs in a multiwafer vapor-phase epitaxial system  

NASA Astrophysics Data System (ADS)

The growth of epitaxial GaAs layers with complex doping structures in a multiple-wafer chloride-transport vapor-phase epitaxial system is reported. The use of kinetically limited growth in a 4-in.-diam reaction chamber permits deposition on multiple large substrates with doping and thickness variations less than + or - 5.5 and + or - 8 percent, respectively. Solid GaAs sources were used in order to eliminate the complications associated with the saturation of liquid Ga. State-of-the-art single- and double-drift IMPATT materials were grown in this reactor and fabricated devices demonstrated excellent RF performance. The results suggest that it is possible to produce device-quality GaAs in large quantities and at low cost on a routine basis using the well-developed chloride-transport method.

Lau, K. M.; Dat, R.

1984-08-01

278

Vapor phase cracking of prompt tars from pyrolysis of sweet gum hardwood  

SciTech Connect

The vapor phase cracking of tar freshly generated by pyrolysis of sweet gum hardwood was studied as a function of temperature (500-800/sup 0/C) at residence times of 0.9 - 2.2 sec to obtain quantitative yields and kinetics. For residence times of about 1 sec, tar conversion ranged from 10 wt% at 500/sup 0/C to 32 wt% at 600/sup 0/C and reached 85 wt% at 800/sup 0/C. The major products of tar cracking are carbon monoxide, hydrogen, carbon dioxide, methane, and ethylene. Kinetic parameters obtained by fitting first-order reaction models to the data allow extents of tar cracking and resulting gaseous product yields to be predicted with an error generally less than ten percent.

Boroson, M.L.; Howard, J.B.; Longwell, J.P.; Peters, W.A.

1986-01-01

279

Growth of thick AlN layer on sapphire (0001) substrate using hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Growth of thick AlN layer was performed directly on sapphire (0001) substrate at 1100 °C by hydride vapor phase epitaxy (HVPE) using AlCl3 and NH3 as source gases. Growth rate over 10 ?m/h was demonstrated by increasing input partial pressure of AlCl3. Also, it was found that the growth rate was sensitive to NH3 input partial pressure (P[stack oNH3 ]), and decreased rapidly with increase of P[stack oNH3 ]. Edge dislocation density estimated from full width at half maximum (FWHM) of X-ray diffraction (XRD) rocking curves was independent of the growth rate.

Yamane, T.; Murakami, H.; Kangawa, Y.; Kumagai, Y.; Koukitu, A.

2005-05-01

280

Heterojunction Hybrid Devices from Vapor Phase Grown MoS2  

PubMed Central

We investigate a vertically-stacked hybrid photodiode consisting of a thin n-type molybdenum disulfide (MoS2) layer transferred onto p-type silicon. The fabrication is scalable as the MoS2 is grown by a controlled and tunable vapor phase sulfurization process. The obtained large-scale p-n heterojunction diodes exhibit notable photoconductivity which can be tuned by modifying the thickness of the MoS2 layer. The diodes have a broad spectral response due to direct and indirect band transitions of the nanoscale MoS2. Further, we observe a blue-shift of the spectral response into the visible range. The results are a significant step towards scalable fabrication of vertical devices from two-dimensional materials and constitute a new paradigm for materials engineering.

Yim, Chanyoung; O'Brien, Maria; McEvoy, Niall; Riazimehr, Sarah; Schafer-Eberwein, Heiko; Bablich, Andreas; Pawar, Ravinder; Iannaccone, Giuseppe; Downing, Clive; Fiori, Gianluca; Lemme, Max C.; Duesberg, Georg S.

2014-01-01

281

Evidence for Family-Meakin Dynamical Scaling in Island Growth and Coalescence during Vapor Phase Deposition  

NASA Astrophysics Data System (ADS)

Using real-time grazing-incidence small-angle x-ray scattering, we find that the processes of island formation and coalescence during the room-temperature vapor phase deposition of aluminum lead to dynamical scaling of the evolving surface morphology. The scaling is quantitatively consistent with the self-similarity predicted by the Family-Meakin model, which was developed to describe liquid droplet deposition, growth, and coalescence. The Family-Meakin model assumes only that atomic diffusion over the substrate between islands or droplets is negligible and that diffusion between impinging islands or droplets is sufficient to give complete coalescence. Therefore the dynamical scaling morphology evolution identified here may be common in the initial stages of those solid film growth processes which proceed by island formation and growth.

Arslan, Leyla Çolakerol; Sanborn, Christopher; Anzenberg, Eitan; Ludwig, Karl F., Jr.

2012-09-01

282

Organometallic Vapor-Phase Epitaxy of GaAs Using Triethylarsenic as Arsenic Source  

NASA Astrophysics Data System (ADS)

GaAs layers are grown by organometallic vapor-phase epitaxy (OMVPE) from trimethylgallium (TMGa) and triethylarsenic (TEAs) source gases under various growth conditions. Mirror-like surfaces are obtained at growth temperatures 560˜780°C and at [TEAs]/[TMGa] ratios 1.3˜7.3. Samples grown at temperatures higher than 670°C exhibit n-type conductivity, while those lower than 600°C exhibit p-type. For n-type samples, the highest Hall mobilities obtained so far are 5270 cm2/Vs and 12200 cm2/Vs at 300 K and 77 K, respectively, with the electron concentration of 7.5× 1015cm-3. Similar to the conventional GaAs layers grown by various techniques, scattering by ionized impurities and space charges caused by some impurities transported with TEAs seems to degrade electrical properties.

Fujita, Shizuo; Uemoto, Yasuhiro; Araki, Soichiro; Imaizumi, Masayuki; Takeda, Yoshikazu; Sasaki, Akio

1988-07-01

283

Vapor-phase staining of cyanoacrylate-fumed latent fingerprints using p-dimethylaminobenzaldehyde.  

PubMed

Contrasting or enhancing of cyanoacrylate ester-fumed latent fingerprints deposited on solvent-sensitive materials such as oil marker writings and rough surface materials such as unglazed earthenware is not easy by conventional dye solutions dipping or dye powder dusting. In this study, a new vapor-phase staining method using p-dimethylaminobenzaldehyde (DMAB) is proposed for staining such materials. DMAB has high volatility and selective absorbability to cyanoacrylate-fumed fingerprints, so that cyanoacrylate-treated samples can be easily stained by leaving them simply in a closed container along with DMAB crystals for 48-96 h at room temperature or in conjunction with the use of mild heating. The stained fingerprint could be excited by UV irradiation (365 nm), and the fluorescent fingerprint was photographed through a UV cut-off filter (420 nm). The new method achieved minimally destructive fluorescent staining for the solvent-sensitive samples and the rough surfaced samples. PMID:22103265

Takatsu, Masahisa; Shimoda, Osamu; Teranishi, Hiroyoshi

2012-03-01

284

Thermal stability of vapor phase deposited self-assembled monolayers for MEMS anti-stiction  

NASA Astrophysics Data System (ADS)

Six different source chemicals (organosilanes) were successfully used for deposition of self-assembled monolayers (SAMs) onto silicon substrates by a vapor phase process. Five different fluorocarbon coatings and one hydrocarbon coating were deposited. The thermal stability of the coatings was studied in detail with respect to degradation as a function of temperature, and for the fluorocarbon coatings also the degradation rate at 400 °C. For fluorocarbon coatings deposited from FDTS a useful lifetime of approximately 90 min at 400 °C was found allowing the coating to survive high temperature MEMS packaging operations, while fluorocarbon coatings deposited from FOTS, FOMDS, FOTES and FOMMS were less stable. The hydrocarbon coating deposited from OTS degrades already at approximately 200 °C. The thermal stability of the SAM coatings was found to be significantly reduced if aggregations from the deposition process are present on the coatings.

Zhuang, Yan Xin; Hansen, Ole; Knieling, Thomas; Wang, Christian; Rombach, Pirmin; Lang, Walter; Benecke, Wolfgang; Kehlenbeck, Markus; Koblitz, Jörn

2006-11-01

285

Kinetics of gas-phase reactions relevant to the chemical vapor deposition of indium compounds  

SciTech Connect

Compounds containing indium are of interest for electronic and optical applications. These compounds include III-V semiconductors such as InP and InAs used in both electronic devices and solar cells, and indium tin oxide, which can be used for optical memory and antireflection coatings. Chemical vapor deposition (CVD) techniques can be used to deposit these materials on a variety of substrates. At the temperatures typically employed (550--900 K), gas-phase chemical reactions involving the indium-containing precursor can occur. The kinetics of trimethylindium pyrolysis are investigated in a flow reactor equipped with a molecular-beam mass-spectrometric sampling system. Data are analyzed using a new computational approach that accounts for heat and mass transport in the reactor. The measured activation energy, 46.2 kcal/mol, is in good agreement with previously reported values.

Allendorf, M.D.; McDaniel, A.H.

1998-03-01

286

Silver nanoisland induced synthesis of ZnO nanostructures by vapor phase transport.  

PubMed

ZnO nanostructures including nanorod and nanotower were synthesized on Ag nanoisland coated Si substrate by thermal evaporation and vapor phase transport at atmospheric pressure. The as-prepared ZnO nanorods and nanotowers were single crystal growing along [0001] direction. The growth of ZnO nanostructures strongly depended on the surface morphology of the nanoisland Ag film deposited by electroless nanoelectrochemistry. The growth mechanism of the ZnO nanostructures was proposed on the basis of experimental data. A strong room-temperature photoluminescence in ZnO nanostructures has been demonstrated. The growth technique would be of particular interest for direct integration in the current silicon-technology-based optoelectronic devices. PMID:16792383

Li, Chun; Fang, Guojia; Ren, Yaoyao; Fu, Qiang; Zhao, Xingzhong

2006-05-01

287

Effects of vapor-phase environmental constituents on macro- to nano-tribological behavior  

NASA Astrophysics Data System (ADS)

When surfaces come into contact, a number of fascinating phenomena occur; adhesion, friction, and wear, each a consequence of material properties, environment conditions and constituents, contacting geometry, applied loads and relative velocities. Changing any of these variables can drastically alter adhesion, friction, and/or wear. Approaches to prevent wear, reduce friction, and control adhesion are determined by the application in question. In many cases, devices requiring lubrication have predetermined geometries, loads, velocities, and are made of specific materials. Effective lubrication and wear prevention then depends on engineering constituents utilized as lubricants. Typically, bulk liquid hydrocarbons are used. As devices shrink in size, bulk lubricants are not practical due to the large capillary forces they create and extreme viscous dampening forces. Microscale devices (i.e. MicroElectroMechanical Systems MEMS) require new technologies for lubrication and wear prevention. This thesis examines the capability of molecular thin films as lubricants and wear prevention films. These films are maintained by utilizing adsorption equilibrium of vapor-phase molecules. Water and various linear alcohol molecules are studied as potential vapor-phase lubricants. Because of the importance of silicon to microscale devices, tribological studies of wear, friction, and adhesion of silicon as a function of alcohol vapor pressure and chain length are studied. Additionally, the effectiveness of these molecular thin films as lubricants for single nano-asperity contact and macrosopic multi-asperity contacts is studied. Adsorption of thin water or alcohol films drastically alters adhesion, friction, and wear. In the case of water adsorption on silicon oxide surface, at low relative humidity, water preferentially adsorbs into the silicon oxide surface in an ice-like structure. As the partial pressure of water increases, liquid water structure is observed to grow on top of the ice-like water structure. As a consequence of structured water at low relative humidities, adhesion between silicon oxide nano-asperity contacts is significantly larger than predicted from capillary forces alone. During sliding in humid environments, chemical wear of silicon oxide is accelerated. Altering the surface chemistry of the silicon oxide surface to prevent water adsorption via chemisorption of self-assembled monolayers is investigated. While these hydrophobic treatments lower the total average surface coverage of water at the interface, water adsorption is not completely prevented. Adsorption of linear alcohols onto the silicon oxide surface is also investigated. In the case of alcohol vapors, monolayer coverage is observed to occur at ˜10% of the saturation pressure of the alcohol. In contrast with water, alcohol is observed to drastically reduce adhesion between nano-scale contacts. The reduction in capillary adhesion is observed to decrease and is inversely proportional to the molar volume. In the case of contact asperities ranging from a single nano-scale asperity to multi-asperity macro-scale systems, alcohol vapor adsorption successfully lubricates (lowers friction) and prevents wear. Inside of the sliding contact region, high-molecular weight oligomeric species are formed via tribochemical reactions from alcohol precursor molecules forming wear protective coatings. Therefore, these oligomeric species/coatings form when and where lubrication is needed most; greatly aiding wear prevention. In the case of silicon based MEMS devices, these films completely prevent wear and increase the lifetime of these devices over 4 to 5 orders of magnitude compared with current "state-of-the-art" self-assembled monolayer coatings.

Asay, David Benjamin

288

Vapor-phase adsorption kinetics of 1-decene on H-terminated Si(100).  

SciTech Connect

We have investigated in situ and in real time vapor-phase self-assembly of 1-decene on Si, using attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIRS). The adsorption of 1-decene on hydrogenated Si(100) results in a decane-terminated hydrophobic surface, indicated by the sessile-drop water contact angle at 107 {+-} 2. This maximum contact angle is achieved at 160 C under 30 mTorr of vapor-phase 1-decene. The fractional surface coverage of decane, calculated from the IR absorbance of C-H stretching vibrational modes near 2900 cm{sup -1}, follows a Langmuir isotherm. The absolute surface coverage calculated from the IR absorbance saturates at 3.2 x 10{sup 14} cm{sup -2}. On the basis of this isotherm, the empirical rate constant (k{prime}{sub 2}) that governs the rate-limiting step in 1-decene adsorption on HF-treated Si(100) is (3.3 {+-} 0.7) x 10{sup -2} min{sup -1}. The thickness and cant angle of the decane monolayer at the saturation coverage are calculated from angle resolved X-ray photoelectron spectroscopy (AR-XPS). The calculated thickness ranges from 8.4 to 18 {angstrom} due to the uncertainty in the attenuation lengths of C(1s) and Si(2p) photoelectrons through the decane layer. For the same uncertainty, the calculated cant angle ranges from 0 to 55{sup o}. Spectroscopic ellipsometry is independently used to approximate the film thickness at 16 {angstrom}. Monitoring the decane monolayer over a period of 50 days using AR-XPS indicates that the Si surface underneath the decane monolayer gets oxidized with time, leading to the degradation of the decane layer.

Kosuri, Madhava R. (University of New Mexico, Albuquerque, NM); Mayer, Thomas Michael; Han, Sang M. (University of New Mexico, Albuquerque, NM); Bunker, Bruce Conrad; Li, Qiming (University of New Mexico, Albuquerque, NM); Gerung, Henry (University of New Mexico, Albuquerque, NM)

2003-06-01

289

Vapor-phase epitaxy of gallium nitride by gallium arc discharge evaporation  

NASA Astrophysics Data System (ADS)

Vapor-phase epitaxy of GaN was performed by combining ammonia with gallium evaporated into an inert gas stream by a DC arc discharge, and letting the mixture pass through a pair of heated graphite susceptors. Growth rates as high as 30 ?m/h were achieved. The growth on the top sample was specular in a large area, and was of high quality as characterized by atomic force microscopy and photoluminescence spectroscopy. The bottom sample had a high density of macroscopic defects, presumably caused by Ga droplets in the gas phase resulting from the arc evaporation process. The experimental growth rate was found to be less than {1}/{3} of values predicted in a computer flow dynamic model of the growth system, and Ga-NH 3 pre-reactions were implicated as the likely cause of the discrepancy. The growth efficiency, calculated to 2%, could arguably be improved by reducing the reactor growth pressure, and by changing the reactor geometry to avoid Ga condensation on walls. Potential advantages of the described growth technique are cheap source materials of high purity and low equipment costs. Furthermore, since no corrosive gasses were used, hardware corrosion and gas-phase impurities can be reduced.

Heikman, S.; Keller, S.; Mishra, U. K.

2006-08-01

290

A NEW VAPOR RECOVERY NOZZLE FOR AIR POLLUTION CONTROL - PHASE II  

EPA Science Inventory

The vapor recovery nozzle is an air pollution control device which relates to Stage II emission control equipment designed to capture gasoline vapors during automobile refueling at service stations. The existing vapor recovery nozzles are difficult to handle, the bellows pr...

291

Waste retrieval sluicing system vapor sampling and analysis plan for evaluation of organic emissions, process test phase III.  

SciTech Connect

This sampling and analysis plan identifies characterization objectives pertaining to sample collection, laboratory analytical evaluation, and reporting requirements for vapor samples obtained to address vapor issues related to the sluicing of tank 241-C-106. Sampling will be performed in accordance with Waste Retrieval Sluicing System Emissions Collection Phase III (Jones 1999) and Process Test Plan Phase III, Waste Retrieval Sluicing System Emissions Collection (Powers 1999). Analytical requirements include those specified in Request for Ecology Concurrence on Draft Strategy/Path Forward to Address Concerns Regarding Organic Emissions from C-106 Sluicing Activities (Peterson 1998). The Waste Retrieval Sluicing System was installed to retrieve and transfer high-heat sludge from tank 241-C-106 to tank 241-AY-102, which is designed for high-heat waste storage. During initial sluicing of tank 241-C-106 in November 1998, operations were halted due to detection of unexpected high volatile organic compounds in emissions that exceeded regulatory permit limits. Several workers also reported smelling sharp odors and throat irritation. Vapor grab samples from the 296-C-006 ventilation system were taken as soon as possible after detection; the analyses indicated that volatile and semi-volatile organic compounds were present. In December 1998, a process test (phase I) was conducted in which the pumps in tanks 241-C-106 and 241-AY-102 were operated and vapor samples obtained to determine constituents that may be present during active sluicing of tank 241-C-106. The process test was suspended when a jumper leak was detected. On March 7, 1999, phase I1 of the process test was performed; the sluicing system was operated for approximately 7 hours and was ended using the controlled shutdown method when the allowable amount of solids were transferred to 241-AY-102. The phase II test was successful, however, further testing is required to obtain vapor samples at higher emission levels and to demonstrate control of the VOC below acceptable limits during the different modes of sluicing. A goal of phase III of the process test will be to obtain representative vapor samples at higher concentrations than those achieved in phase I and phase I1 of the process test. During phase III of the process test, vapor samples will be obtained from the 296-C-006 ventilation system stack. Ambient air samples will also be obtained at two locations within 241-C Tank Farm. Results will be used to address the following: (1) Provide gas composition data that can be used to determine personnel protective measures, (2) Provide gas composition data that can be used for control equipment selection and design, if required, and (3) Substantiate that ammonia and organic emissions are below regulatory thresholds during the test.

SASAKI, L.M.

1999-05-19

292

19 CFR 159.5 - Cigars, cigarettes, and cigarette papers and tubes.  

Code of Federal Regulations, 2013 CFR

...Cigars, cigarettes, and cigarette papers and tubes. 159.5 Section 159.5 Customs...cigarettes, and cigarette papers and tubes. The internal revenue taxes imposed...cigarettes, and cigarette papers and tubes under section 5701 or 7652, Internal...

2013-04-01

293

[Quantitative determination of nitrogen oxide in cigarette smoke by means of chemiluminescence (author's transl)].  

PubMed

A measuring method with a chemiluminescence-analyzer is developed for determining the content of nitrogen oxide in cigarette smoke. This method is suitable for puff/puff analysis. It could be demonstrated that a determination of fresh smoke is necessary as nitrogen oxides react very quickly with other constituents of the vapor phase. Measured values have to be corrected for a quench factor in analogy to the CO2 concentration, as carbon dioxide shows an influence on the measuring sensitivity of the chemiluminescence-analyzer. PMID:835344

Klimisch, H J; Kirchheim, E

1977-01-01

294

Method for the generation of variable density metal vapors which bypasses the liquidus phase  

DOEpatents

The present invention provides a method for producing a metal vapor that includes the steps of combining a metal and graphite in a vessel to form a mixture; heating the mixture to a first temperature in an argon gas atmosphere to form a metal carbide; maintaining the first temperature for a period of time; heating the metal carbide to a second temperature to form a metal vapor; withdrawing the metal vapor and the argon gas from the vessel; and separating the metal vapor from the argon gas. Metal vapors made using this method can be used to produce uniform powders of the metal oxide that have narrow size distribution and high purity.

Kunnmann, Walter (Stony Brook, NY); Larese, John Z. (Rocky Point, NY)

2001-01-01

295

Evaluation of PCDD/F congener partition in vapor/solid phases of waste incinerator flue gases.  

PubMed

Activated carbon injection (ACI) is commonly used to control PCDD/F (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans) emissions from stationary sources. In this study, the characteristics of PCDD/Fs emitted from one municipal waste incinerator (MWI) and two industrial waste incinerators (IWI-1 and IWI-2) that apply activated carbon systems for controlling the emissions are investigated via intensive stack sampling. MWI and IWI-1 are equipped with ACI and bag filters (BF) while IWI-2 is equipped with a fixed activated carbon bed (FCB). Results indicate that most PCDD/Fs in flue gas downstream of ACI+BF exist in vapor phase (over 90%) while most PCDD/ Fs exist in solid phase (over 60%) downstream of FCB. For MWI and IWI-1, the removal efficiencies of vapor and solid-phase PCDD/Fs are 98.5-99.6% and 99.8-99.9%, respectively. In addition,the removal efficiencies of vapor- and solid-phase PCDD/Fs are 84.5% and -13.4% in IWI-2, respectively. The results also indicate that the partition of vapor/solid-phase PCDD/F is affected by the type of the air pollutant control devices (APCDs) applied upstream and the particulate matter concentration in flue gas. On the basis of the sampling results of waste incinerators, this study preliminarily establishes the equations for predicting vapor/solid-phase PCDD/F partition in flue gases downstream of various APCDs including cyclone (CY), electrostatic precipitator (EP), FCB, ACI+BF, and selective catalytic reduction system (SCR). PMID:16295870

Chi, Kai Hsien; Chang, Moo Been

2005-10-15

296

Determination of the Adsorption Isotherm of Vapor-Phase Mercury Chloride on Powdered Activated Carbon Using Thermogravimetric Analysis  

Microsoft Academic Search

This study investigated the use of thermogravimetric analysis (TGA) to determine the adsorptive capacity and adsorption isotherm of vapor-phase mercury chloride on powdered activated carbon (PAC). The technique is commonly applied to remove mercury-containing air pollutants from gas streams emitted from municipal solid waste incinerators. An alternative form of powdered activated carbon derived from a pyrolyzed tire char was prepared

Hsun-Yu Lin; Chung-Shin Yuan; Wei-Ching Chen; Chung-Hsuang Hung

2006-01-01

297

Screening of alkali-promoted vapor-phase-synthesized molybdenum sulfide catalysts for the production of alcohols from synthesis gas  

Microsoft Academic Search

A series of molybdenum sulfide catalysts has been prepared using vapor-phase decomposition of molybdenum hexacarbonyl in an atmosphere of hydrogen sulfide. The effect of the decomposition conditions on the properties of the molybdenum sulfides formed has been studied over a temperature range of 300--900 C. These materials, when promoted with alkali, have been found to have a high activity for

Zhenyu Liu; Xianguo Li; Michael R. Close; Edwin L. Kugler; Jeffrey L. Petersen; Dady B. Dadyburjor

1997-01-01

298

Atmospheric mercury in the vapor phase, and in fine and coarse particulate matter at Perch River, New York  

Microsoft Academic Search

Daily samples of size segregated atmospheric particulate matter (da < 2.5 ?m, and 2.5 ?m < da < 10 ?m), and vapor-phase mercury have been collected at five locations in upstate New York over a period of two years. Atmospheric concentrations were determined for mercury and, in the particulate matter, for up to 38 other elements by Instrumental Neutron Activation

Michael Ames; Gulen Gullu; Ilhan Olmez

1998-01-01

299

Use of dissolved and vapor-phase gases to investigate methanogenic degradation of petroleum hydrocarbon contamination in the subsurface  

Microsoft Academic Search

At many sites contaminated with petroleum hydrocarbons, methanogenesis is a significant degradation pathway. Techniques to estimate CH4 production, consumption, and transport processes are needed to understand the geochemical system, provide a complete carbon mass balance, and quantify the hydrocarbon degradation rate. Dissolved and vapor-phase gas data collected at a petroleum hydrocarbon contaminated site near Bemidji, Minnesota, demonstrate that naturally occurring

Richard T. Amos; K. Ulrich Mayer; Barbara A. Bekins; Geoffrey N. Delin; Randi L. Williams

2005-01-01

300

OM-VPE growth of Mg-doped GaAs. [OrganoMetallic-Vapor Phase Epitaxy  

NASA Technical Reports Server (NTRS)

The epitaxial growth of Mg-doped GaAs by the organometallic vapor phase epitaxial process (OM-VPE) has been achieved for the first time. The doping is controllable over a wide range of input fluxes of bis (cyclopentadienyl) magnesium, (C5H5)2Mg, the organometallic precursor to Mg.

Lewis, C. R.; Dietze, W. T.; Ludowise, M. J.

1982-01-01

301

The solubility of gallium oxide in vapor and two-phase fluid filtration in hydrothermal systems  

NASA Astrophysics Data System (ADS)

The solubility of gallium and aluminum oxides in gas phase in the system Ga2O3 (Al2O3)-HCl-H2O was studied at 150-350°C and pressure up to saturated vapor. The concentration of gallium increases with the increasing of HCl pressure. The formulae of gallium gaseous specie was determined as GaOHCl2. The constant of gallium oxide solubility reaction was calculated at 150, 200, 250, 300 and 350°C. The concentration of aluminum in gas phase is insignificant in the same conditions. The possibility of gallium transportation in gas phase with small quantity of Al allow to divide this elements in hydrothermal processes with gas phase. The Ga/Al ratio in muscovite can be used as the indicator of gas phase separation and condensation. This indicator was not considered in the geochemical literature earlier. The separation of gas and liquid phases was determined in Akchatau (Kazahstan) and Spokoinoe (Russia) greisen W deposit by carbon isotope fractionation of carbon dioxide in fluid inclusion. The important feature of both ore mains is heterogenization and boiling of ore-forming fluids. Greisen ore bodies are formed as a result of strongly focused solution flow in the T-P gradient fields. It is possible to divide ore bodies of Akchatau in two types: muscovite and quartz. Muscovite type veins are thin and have small metasyntactic zone. Quartz type veins are localized in fault with large vertical extent (500 m) and content the large quantity of wolframite. These veins formed in condition of significant pressure decreasing from 2.5 to 0.5 kbar with fluid boiling. Gas and liquid phase separation specifies the vertical zonality of quartz type veins. The gas phase with the high gallium concentration is separated from a flow of liquid phase. Liquid phase react with the granites forming greisen metasomatites. Condensation of the gas phase in upper parts of massive produces the increasing of Ga/Al ratio in muscovite 3-5 times more, then in granites and bottom part of vein (from 2×10-4 to 8×10-4 mass ratio). The muscovite type veins has no separation between gas and liquid due to there thickness and small pressure gradient. There is no difference in Ga/Al ratio in muscovite from this veins. The Spokoinoe deposit is classified by mineralized dome type. The heterogenization of fluid occurs in H2O-CO2 system for water phase and carbon dioxide with temperature decreasing. Two-phase flow is separated in granite, forming greisen metosomatites. The Ga/Al ratio in rock increase up to 3 times to the upper part of metasomatitic zone. The Ga/Al ratio in muscovite can be applied for other hydrothermal systems for geochemical indicator of gas phase separation and condensation zone determination. This work is supported by RFBR project 10-05-00670 and 10-05-00320.

Bychkov, Andrew; Matveeva, Svetlana; Nekrasov, Stanislav

2010-05-01

302

Growth behavior of GaSb by metal organic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

The growth mechanisms of GaSb in a metal-organic vapor-phase epitaxy (MOVPE) system were studied for both trimethyl gallium (TMG)/trimethyl antimony (TMSb) and triethyl gallium (TEG)/TMSb growth chemistries. The effect of growth temperature and precursor mole fractions on GaSb growth rate was determined experimentally. Numerical analysis of the reactor and growth process was described in a combined chemical-thermal-fluid flow model. A Langmuir-Hinshelwood-type mechanism involving a surface reaction between adsorbed monomethyl gallium (MMG) and adsorbed monomethyl antimony (MMSb) or adsorbed Ga and adsorbed MMSb was proposed for the growth of GaSb by MOVPE using TMG or TEG and TMSb chemistries, respectively. The chemical model for TMG/TMSb chemistry included bounds on the surface chemistry derived for the range of V/III precursor ratio which were observed to lead to a second phase, i.e., elemental Ga or Sb, formation. Two growth regimes were observed for TMG/TMSb chemistry: above 575 °C the growth rate was mass transfer controlled whereas for lower temperatures it is kinetically limited. No such temperature dependence has been found for the TEG/TMSb chemistry over all experimental employed ranges of growth parameters.

Rathi, Manish K.; Hawkins, Brian E.; Kuech, Thomas F.

2006-11-01

303

The role of gas-phase reactions in modeling of the forced-flow chemical vapor infiltration process  

Microsoft Academic Search

An analytical model is presented, which includes the effects of both gas-phase and surface reactions, and the pressure changes due to the chemical reactions in the forced-flow chemical vapor infiltration (FCVI) process. For the FCVI process controlled by the gas-phase reactions, improvements of the process by using the forced-flow are limited. However, for the FCVI process controlled by the surface

Ching Yi Tsai; J. N. Reddy; Seshu B. Desu; Chien C. Chiu

1993-01-01

304

Liquid-vapor phase equilibria and distillation in the hexane-dimethylformamide-benzene and heptane-dimethylformamide-benzene systems  

SciTech Connect

Data are required on the liquid-vapor phase equilibrium in systems containing a nonaromatic hydrocarbon, benzene and DMF for a mathematical model of the extractive distillation of benzene with DMF. Therefore, data are given in this paper on the liquid-vapor equilibrium in the hexane-DMF-benzene and heptane-DMF-benzene systems at atmospheric pressure. The proposed model for the extractive distillation of benzene concentrates using DMF permits one to select a mode, in which benzene is obtained in purity exceeding the standard requirement and in high yield.

Stepanova, E.I.; Kharisov, M.A.; Kukharenok, I.S.; Petrova, V.F.; Sabylin, I.I.; Strel'nikov, K.I.

1986-04-20

305

Hydride vapor phase epitaxy growth of GaN, InGaN, ScN, and ScAIN  

Microsoft Academic Search

Chemical vapor deposition (CVD); hydride vapor phase epitaxy (HVPE); gallium nitride (GaN); indium gallium nitride (InGaN); scandium nitride (ScN); scandium aluminum nitride (ScAlN); semiconductors; thin films; nanowires; III nitrides; crystal growth\\u000a\\u000a-\\u0009We studied the HVPE growth of different III nitride materials. For GaN the aim was creating thick high quality films as a basis for white light LEDs, Blu-ray

T. Bohnen

2010-01-01

306

Step structure of GaInAsSb grown by organometallic vapor phase epitaxy  

SciTech Connect

The surface step structure of GA{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} grown by organometallic vapor phase epitaxy on GaSb substrates has been studied by atomic force microscopy. Epilayers were grown at 525 C and 575 C on (001) GaSb substrates misoriented 2{degree} toward (101) or 6{degree} toward (1{bar 1}1)B. For Ga{sub 0.88}In{sub 0.12}Sb{sub 0.9} grown at 575 C, the surface exhibits step-bunching on both types of substrates. When the composition is increased to Ga{sub 0.86}In{sub 0.14}As{sub 0.12}Sb{sub 0.88}, the periodic step structure breaks down and the surface becomes irregular. The deterioration of the step structure is a consequence of phase separation at the surface of the metastable GaInAsSb epilayer, which leads to the formation of GaAs- and InSb-rich regions. The photoluminescence (PL) of such layers show significant broadening due to carrier recombination in the lower energy gap InSb-rich quaternary regions. On the other hand, the surface of GaInAsSb epilayers grown at a lower temperature of 525 C is vicinal with steps heights of one to two monolayers. The PL FWHM values are considerably smaller for these layers. This improvement in material quality is related to smaller adatom lifetimes at the lower growth temperature. The importance of surface kinetics as it influences the step structure and thermodynamically driven phase separation is discussed.

Wang, C.A.

2000-01-01

307

m-Plane Homoepitaxy and Equilibrium Crystal Shapes of Gallium Nitride by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

Nonpolar and semipolar growth of GaN has been shown to offer a promising path for high performance devices. These non-basal plane orientations allow for minimization of the polarization effects seen in c-plane GaN which cause spatial separation of the electron and hole wavefunctions (Quantum Confined Stark Effect). Yet despite the advantages these planes present, there remains consistent problems in both their growth and the lack of substrates. This dissertation focuses on the growth of these nonpolar and semipolar planes, in particular the homoepitaxy of m-plane GaN. The equilibrium crystal shape of GaN and its stable facets were also investigated. It is hoped that with this work, progress is made towards low defect large area nonpolar and semipolar substrates and their improved vapor phase growth. Work was initially done on m-plane regrowth by hydride vapor phase epitaxy. Extended defect generation, in particular basal plane stacking faults (BPSF), and poor morphology control are consistent problems in m-plane growth. These issues have prevented the expansion and multiplication of m-plane GaN substrates. In this work the effects of carrier gas were investigated on m-plane regrowth. Hydrogen carrier gas was shown to create highly faceted 3D nucleation. These islands had exposed N-face facets which lead to BPSF generation. In contrast, nitrogen carrier gas lead to 2D growth and thus minimized BPSF generation. These stacking faults were then characterized by both reciprocal space mapping and cathodolumienscence where type I1 and I2 faults were observed in the regrown GaN. Further work was done in exploring the equilibrium crystal shapes of GaN under varying growth conditions. Selective area growth experiments were done on high quality bulk m-plane GaN substrates where GaN facets were exposed to show the stable polar, semipolar and nonpolar planes. From these facets the kinetic Wulff plots for GaN were constructed. This work highlights the stable growth conditions for nonpolar and semipolar GaN and leads to improved growth conditions. AlN growth by HVPE is also investigated in this dissertation with work being done on thick AlN growth on patterned sapphire substrates (PSS). These templates were made for the purpose of substrates for UV LEDs.

Bryant, Benjamin Nathaniel

308

Former Cigarette Smokers.  

National Technical Information Service (NTIS)

In 2000, 67 percent of those aged 12 or older (over 148 million persons) in the United States reported any cigarette use during their lifetime. Among smokers of at least 100 cigarettes, 42 percent reported not smoking during the past year. Males who smoke...

2002-01-01

309

Cigarette smoking and asthma  

Microsoft Academic Search

Cigarette smoking and asthma. C. Suppli Ulrik, P. Lange. Cigarette smoking is a well-know health hazard, probably not least for patients suffering from asthma. This review gives a short overview concerning the effects of passive and active smoking on the inception and out- come with regard to longitudinal changes in lung function and mortality for patients with asthma. Substantial evidence

C. Suppli Ulrik; P. Lange

2001-01-01

310

How Youths get Cigarettes.  

National Technical Information Service (NTIS)

In 2001, over 3 million youths aged 12 to 17 had smoked cigarettes during the past month. About three fifths of past month smokers aged 12 to 17 had a friend or relative buy cigarettes for them at least one time during the past month. Among youths who smo...

2002-01-01

311

Real-time GPS sensing of atmospheric water vapor: Precise point positioning with orbit, clock, and phase delay corrections  

NASA Astrophysics Data System (ADS)

recent development of the International Global Navigation Satellite Systems Service Real-Time Pilot Project and the enormous progress in precise point positioning (PPP) techniques provide a promising opportunity for real-time determination of Integrated Water Vapor (IWV) using GPS ground networks for various geodetic and meteorological applications. In this study, we develop a new real-time GPS water vapor processing system based on the PPP ambiguity fixing technique with real-time satellite orbit, clock, and phase delay corrections. We demonstrate the performance of the new real-time water vapor estimates using the currently operationally used near-real-time GPS atmospheric data and collocated microwave radiometer measurements as an independent reference. The results show that an accuracy of 1.0 ~ 2.0 mm is achievable for the new real-time GPS based IWV value. Data of such accuracy might be highly valuable for time-critical geodetic (positioning) and meteorological applications.

Li, Xingxing; Dick, Galina; Ge, Maorong; Heise, Stefan; Wickert, Jens; Bender, Michael

2014-05-01

312

Deep hole traps in undoped n-GaN films grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Deep hole traps were studied in bulk free-standing GaN crystals and in thinner (10-20 ?m) GaN films prepared by hydride vapor phase epitaxy (HVPE) on sapphire. Six hole traps in different combinations were detected in these crystals, H1 (activation energy 0.92-0.94 eV), H2 (0.55 eV), H3 (0.65-0.7 eV), H4 (0.85-0.9 eV), H5 (1.1-1.2 eV), and H6 (0.95-1.05 eV). The dominant traps in all samples were the H5 and H6 traps that were attributed, respectively, to gallium vacancy complexes with oxygen (VGa-O) and substitutional carbon related centers. We associate the H5 hole traps with the red luminescence bands, the H4 hole traps with the green luminescence bands, and the H6 hole traps with the yellow luminescence bands often observed in HVPE GaN. These attributions are based on the low energy thresholds of the deep traps optical excitation spectra and the depth of the respective trap levels.

Lee, In-Hwan; Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Usikov, A. S.; Helava, H.; Makarov, Yu. N.; Pearton, S. J.

2014-06-01

313

Acceptance Testing of the Vapor Phase Catalytic Ammonia Removal Engineering Development Unit  

NASA Technical Reports Server (NTRS)

This paper describes the results of acceptance testing of the Vapor Phase Catalytic Ammonia Removal (VPCAR) technology. The VPCAR technology is currently being developed by NASA as a Mars transit vehicle water recycling system. NASA has recently completed a grant to develop a next generation VPCAR system. This grant was peer reviewed and funded through the Advanced Life Support (ALS) National Research Announcement (NRA). The grant funded a contract with Water Reuse Technology Inc. to construct an engineering development unit. This contract concluded with the shipment of the final deliverable to NASA on 8/31/03. The objective of the acceptance testing was to characterize the performance of this new system. This paper presents the results of mass power, and volume measurements for the delivered system. In addition, product water purity analysis for a Mars transit mission and a planetary base wastewater ersatz are provided. Acoustic noise levels, interface specifications and system reliability results are also discussed. An assessment of the readiness of the technology for human testing and recommendations for future improvements are provided.

Flynn, Michael; Fisher, John; Kliss, Mark; Tleimat, Maher; Quinn, Gregory; Fort, James; Nalette, Tim; Baker, Gale

2005-01-01

314

Identification of Si and O donors in hydride-vapor-phase epitaxial GaN  

NASA Astrophysics Data System (ADS)

Donor impurity excitation spectra in the infrared from two high-quality, not-intentionally doped, hydride-vapor-phase epitaxial GaN wafers are reported. Two previously observed shallow donors which we designate N1 and N2 were observed in both wafers. However, spectra of one wafer are dominated by N1 and spectra of the other by N2. A comparison of infrared and secondary ion mass spectroscopic data allows identification of N1 as Si and N2 as O. Silicon is the shallowest uncompensated donor in these samples with an activation energy of 30.18+/-0.1 meV in the freestanding Samsung wafer. The activation energy of O is found to be 33.20+/-0.1 meV. An unidentified third donor with an activation energy of 31.23+/-0.1 meV also was observed. Integrated absorption cross sections are found to be 8.5×10-14 cm for Si and 8.6×10-14 cm for O.

Moore, W. J.; Freitas, J. A.; Braga, G. C. B.; Molnar, R. J.; Lee, S. K.; Lee, K. Y.; Song, I. J.

2001-10-01

315

Reduction of as carryover by PH 3 overpressure in metalorganic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

InGaAs/InP superlattices were grown to analyze the As carryover at the InP-on-InGaAs interface in metalorganic vapor-phase epitaxy. The analysis through the double crystal X-ray diffractometry and the subsequent simulation revealed that a InAsP transient layer is formed at the interface due to As carryover to the InP layer. The change of PH 3 flow rate during the growth interruption is found to be effective in controlling the desorption of As from the deposits on the reactor wall. It is believed that the increase of PH 3 flow rate accelerates the As desorption and thus the As depletion is completed in a shorter time. In addition, the increased amount of desorbed As helps to protect the InGaAs surface during PH 3 flow. The high PH 3 flow and the corresponding interruption time provide nearly As-free InP-on-InGaAs interface.

Ryu, Sang-Wan; Jeong, Weon Guk; Kim, In; Kim, Hee-Dae; Kim, Hak-Hwan; Choe, Byung-Doo; Park, Seoung-Hwan

1997-08-01

316

GaAs c(4×4) surface structure in organometallic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

While GaAs(001) surface reconstructions have been studied extensively in the ultrahigh-vacuum environment associated with molecular-beam epitaxy (MBE), comparatively little is known of these structures in the chemically rich environment associated with organometallic vapor-phase epitaxy (OMVPE). This work presents a structural study of the c(4×4) surface reconstruction stabilized in an arsenic-rich OMVPE environment. Measurements of the in-plane structure were performed in situ using grazing-incidence x-ray scattering with synchrotron radiation. Structural refinement confirms the presence of arsenic-arsenic dimers arranged with the c(4×4) symmetry. In concurrence with similar studies performed in the MBE environment, it is found that the surface is a mixture of structural domains composed of two- and three-dimer variants of the c(4×4) reconstruction. Atomic positions associated with these structures are presented. The size, aspect ratio, and orientation of the reconstructed regions are shown to be closely related to the atomic step geometry on the crystal surface.

Payne, A. P.; Fuoss, P. H.; Kisker, D. W.; Stephenson, G. B.; Brennan, S.

1994-05-01

317

New vanadium dopant precursor for GaAs growth by metalorganic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

Vanadium-doped GaAs was grown by metalorganic vapor-phase epitaxy (MOVPE) using vanadium (IV) chloride VCl 4 as a novel dopant source. The optimum growth conditions were achieved using reflectometry with a 632.8 nm laser beam. A reduction in the growth rate of V-doped GaAs was observed and attributed to the etching by Cl species associated to the use of high flow of VCl 4. The incorporation of vanadium in GaAs was investigated by secondary ion mass spectroscopy (SIMS) measurements. Samples were also characterized by room temperature Hall effect. Electron concentrations ranging from 10 13 to 2×10 17 cm -3 have been obtained. The maximum resistivity is about 715 ? cm. For all samples high compensation ratio larger than 0.7 was observed. The comparison between only silicon-doped GaAs and silicon-vanadium Co-doped GaAs, showed that there was no effect in modifying the compensation ratio.

Rebey, A.; Bchetnia, A.; Benjeddou, Ch; El Jani, B.; Gibart, P.

1998-01-01

318

Surface organization of homoepitaxial InP films grown by metalorganic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

We present a systematic study of the morphology of homoepitaxial InP films grown by metalorganic vapor-phase epitaxy which are imaged with ex situ atomic force microscopy. These films show a dramatic range of different surface morphologies as a function of the growth conditions and substrate (growth temperature, V/III ratio, and miscut angle <0.6? and orientation toward A or B sites), ranging from stable step flow to previously unreported strong step bunching, over 10 nm in height. These observations suggest a window of growth parameters for optimal quality epitaxial layers. We also present a theoretical model for these growth modes that takes account of deposition, diffusion, and dissociation of molecular precursors, and the diffusion and step incorporation of atoms released by the precursors. The experimental conditions for step flow and step bunching are reproduced by this model, with the step bunching instability caused by the difference in molecular dissociation from above and below step edges, as was discussed previously for GaAs (001).

Gocalinska, A.; Manganaro, M.; Pelucchi, E.; Vvedensky, D. D.

2012-10-01

319

Optical Properties of ZnO Soccer-Ball Structures Grown by Vapor Phase Transport  

NASA Astrophysics Data System (ADS)

ZnO soccer balls were grown on an Au-catalyzed Si(100) substrate by vapor phase transport (VPT) with a mixture of zinc oxide and graphite powders. Temperature-dependent PL was carried out to investigate the mechanism governing the quenching behavior of the PL spectra. From the PL spectra of the ZnO soccer balls at 10 K, several PL peaks were observed at 3.365, 3.318, 3.249, and 3.183 eV corresponding to excitons bound to neutral donors (D\\text{oX), a donor--acceptor pair (DAP), first-order longitudinal optical phonon replica of donor--acceptor pair (DAP-1LO), and DAP-2LO, respectively. The mixed system composed of the free exciton (FX) and D\\text{oX and the DAP radiative lifetimes were estimated with a theoretical relation between the lifetime and the spectral width. The exciton radiative lifetimes were observed to increase linearly with temperature.

Nam, Giwoong; Lee, Sang-heon; Kim, Soaram; Kim, Min Su; Kim, Do Yeob; Yim, Kwang Gug; Lee, Dong-Yul; Kim, Jin Soo; Kim, Jong Su; Son, Jeong-Sik; Kim, Sung-O; Jung, Jae Hak; Leem, Jae-Young

2012-02-01

320

Postsynthesis vapor-phase functionalization of MCM-48 with hexamethyldisilazane and 3-aminopropyldimethylethoxylsilane for bioseparation applications.  

PubMed

MCM-48 was surface modified via vapor-phase reactions with hexamethyldisilazane (CH(3)-MCM-48) and 3-aminopropyldimethylethoxysilane (NH(2)-MCM-48). (29)Si NMR confirmed that the resulting materials contained covalently attached trimethylsilane and 3-aminopropyldimethylsilane moieties, both important functionalities for bioseparation applications. The surface coverage was approximately 1.8 and 0.9 groups per nm(2), respectively. The X-ray diffraction patterns and the narrow pore size distributions obtained from the gas sorption isotherms showed that the modified materials retained the characteristic pore structure of the underlying MCM-48 material. CH(3)-MCM-48 exhibited significantly improved hydrolytic stability over the unmodified MCM-48 under the aqueous conditions tested, whereas NH(2)-MCM-48 appeared to be less stable than the unmodified MCM-48. The decrease in stability is most likely due to the nature of the attachment of the 3-aminopropyldimethylsilane moiety, where the conversion of surface silanol groups is limited by H bonding with the amino end, leading to a 50% lower surface concentration and resulting in an increased likelihood of nucleophilic attack on the silica surface, enhancing the rate of hydrolysis. Hexamethyldisilazane thus appears to be a superior functional group for modifying the MCM-48 surface. PMID:16853067

Daehler, Antje; Boskovic, Sasha; Gee, Michelle L; Separovic, Frances; Stevens, Geoffrey W; O'Connor, Andrea J

2005-09-01

321

Environmentally Compatible Vapor-Phase Corrosion Inhibitor for Space Shuttle Hardware  

NASA Technical Reports Server (NTRS)

USA-SRB Element is responsible for the assembly and refurbishment of the non-motor components of the SRB as part of Space Shuttle. Thrust Vector Control (TVC) frames structurally support components of the TVC system located in the aft skirt of the SRB. TVC frames are exposed to the seacoast environment after refurbishment and, also, to seawater immersion after splashdown, and during tow-back to CCAFS-Hangar AF refurbishment facilities. During refurbishment operations it was found that numerous TVC frames were experiencing internal corrosion and coating failures, both from salt air and seawater intrusions. Inspectors using borescopes would visually examine the internal cavities of the complicated aluminum alloy welded tubular structure. It was very difficult for inspectors to examine cavity corners and tubing intersections and particularly, to determine the extent of the corrosion and coating anomalies. Physical access to TVC frame internal cavities for corrosion removal and coating repair was virtually impossible, and an improved method using a Liquid (water based) Vapor-phase Corrosion Inhibitor (LVCI) for preventing initiation of new corrosion, and mitigating and/or stopping existing corrosion growth was recommended in lieu of hazardous paint solvents and high VOC/solvent based corrosion inhibitors. In addition, the borescopic inspection method used to detect corrosion, and/or coating anomalies had severe limitations because of part geometry, and an improved non-destructive inspection (NDI) method using Neutron Radiography (N-Ray) was also recommended.

Novak, Howard L.; Hall, Phillip B.; McCool, Alex (Technical Monitor)

2001-01-01

322

Metalorganic vapor-phase epitaxy of GaN from trimethylgallium and tertiarybutylhydrazine  

NASA Astrophysics Data System (ADS)

Gallium nitride (GaN) layers have been epitaxially grown by the metalorganic vapor-phase epitaxy technique using trimethylgallium (TMG) and tertiarybutylhydrazine (TBHy) as the reactants at temperatures ranging from 923 to 958 K and a low pressure of 10 Torr. A film growth model based on the Langmuir-Hinshelwood-type reaction is established to describe the growth behavior of GaN from TMG and TBHy. By model fitting, the experimental growth rate data, the adsorption equilibrium constant of TBHy is found to be 1/7 that of TMG at the above temperature range, indicating the possibility to obtain stoichiometric GaN films at quite small V/III precursor feed ratios. Additionally, a comparison of the carbon incorporation when dimethylhydrazine (DMHy) is used as the nitrogen source is also made. The result shows that the films formed using TBHy have much less carbon content than those formed using DMHy. The ?-hydride elimination in the t-butyl ligand of TBHy occurs to form a stable hydrocarbon species, thus taking away the carbon contaminants might explain this phenomenon.

Hsu, Yu Jen; Hong, Lu Sheng; Tsay, Jing En

2003-05-01

323

Hydride vapor phase epitaxy and characterization of high-quality ScN epilayers  

NASA Astrophysics Data System (ADS)

The heteroepitaxial growth of ScN films was investigated on various substrates by hydride vapor phase epitaxy (HVPE). Single crystalline mirror-like ScN(100) and ScN(110) layers were successfully deposited on r- and m-plane sapphire substrates, respectively. Homogeneous stoichiometric films (N/Sc ratio 1.01 ± 0.10) up to 40 ?m in thickness were deposited. Their mosaicity drastically improved with increasing the film thickness. The band gap was determined by optical methods to be 2.06 eV. Impurity concentrations including H, C, O, Si, and Cl were investigated through energy dispersive X-ray spectrometry and secondary ion mass spectrometry. As a result, it was found that the presence of impurities was efficiently suppressed in comparison with that of HVPE-grown ScN films reported in the past, which was possible thanks to the home-designed corrosion-free HVPE reactor. Room-temperature Hall measurements indicated that the residual free electron concentrations ranged between 1018-1020 cm-3, which was markedly lower than the reported values. The carrier mobility increased monotonically with the decreasing in carrier concentration, achieving the largest value ever reported, 284 cm2 V-1 s-1 at n = 3.7 × 1018 cm-3.

Oshima, Yuichi; Víllora, Encarnación G.; Shimamura, Kiyoshi

2014-04-01

324

Progress in large area organometallic vapor phase epitaxy for III-V multijunction photovoltaics  

NASA Astrophysics Data System (ADS)

Multijunction solar cells are fabricated using organometallic vapor phase epitaxy (OMVPE) to deposit subcells of GaInP and GaInAs on 150 mm diameter Ge substrates. We review the general challenges of achieving solar cell epitaxial growth on 150 mm dia. Ge and discuss basic GaInP material characterization. Metamorphic GaInP/GaInAs/Ge C4MJ epitaxial layers are characterized by in-situ curvature measurements during growth. A 98.5% relaxation is measured by high resolution X-ray diffraction reciprocal space mapping, and a threading dislocation density of 1.3×105 cm-2 is measured by cathodoluminescence in active regions of the device. Test batches of 20 kWp of cells, 1.0 cm2 in aperture area, are grown and fabricated on 100 mm and 150 mm dia. Ge wafers and average 40.2% and 40.1% efficiency, respectively, under 50 W/cm2 AM1.D illuminated current-voltage (LIV) testing. Finally, we demonstrate very large area, >72 cm2, triple junction XTJ space devices, averaging 29.3% efficiency for 73 such devices under space LIV testing (0.1353 mW/cm2, 28 °C, AM0).

Fetzer, C. M.; Liu, X. Q.; Chang, J.; Hong, W.; Palmer, A.; Bhusari, D.; Jun, B.; Lau, M.; Lee, H.

2012-08-01

325

Thermodynamic analysis of III-V semiconductor alloys grown by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

A thermodynamic analysis has been applied to systematically study III-V semiconductor alloy deposition, including nitrides grown by metalorganic vapor phase epitaxy. The predicted solid compositions of a number of ternary and quaternary alloys, including AlxGa1-xPyAs1-y, are compared with experimental data. For phosphorus-containing alloys, introduction of a parameter f representing incomplete PH3 pyrolysis yields good agreement with experimental data. It is shown that the input mole fraction of the group III metalorganic sources influences the incorporation of P into the solid for these alloys. Solid composition is also calculated for nitride alloys as a function of inlet gas concentration. To date, thermodynamic models have been applied solely to predict N solubility limits for nitride alloys where mixing occurs on the group V sublattice. The present model is used to predict N solid compositions in ternary and quaternary alloys, and it is demonstrated that these values are below the theoretical solubility limits for In-containing nitrides. The role of H2 in the carrier gas is investigated for III-N-V, III-III-N-V, and III-N-V-V systems.

Asai, Toshihiro; Dandy, David S.

2000-10-01

326

Vapor phase polymerization deposition of conducting polymer/graphene nanocomposites as high performance electrode materials.  

PubMed

In this paper, we report chemical vapor phase polymerization (VPP) deposition of novel poly(3,4-ethylenedioxythiophene) (PEDOT)/graphene nanocomposites as solid tantalum electrolyte capacitor cathode films. The PEDOT/graphene films were successfully prepared on porous tantalum pentoxide surface as cathode films through the VPP procedure. The results indicated that the high conductivity nature of PEDOT/graphene leads to the decrease of cathode films resistance and contact resistance between PEDOT/graphene and carbon paste. This nanocomposite cathode film based capacitor showed ultralow equivalent series resistance (ESR) ca. 12 m? and exhibited better capacitance-frequency performance than the PEDOT based capacitor. The leakage current investigation revealed that the device encapsulation process does not influence capacitor leakage current, indicating the excellent mechanical strength of PEDOT-graphene films. The graphene showed a distinct protection effect on the dielectric layer from possible mechanical damage. This high conductivity and mechanical strength graphene based conducting polymer nanocomposites indicated a promising application future for organic electrode materials. PMID:23621384

Yang, Yajie; Li, Shibin; Zhang, Luning; Xu, Jianhua; Yang, Wenyao; Jiang, Yadong

2013-05-22

327

Environmentally Compatible Vapor-Phase Corrosion Inhibitor for Space Shuttle Hardware  

NASA Technical Reports Server (NTRS)

USA-SRB Element is responsible for the assembly and refurbishment of the non-motor components of the SRB as part of Space Shuttle. Thrust Vector Control (TVC) frames structurally support components of the TVC system located in the aft skirt of the SRB. TVC frames are exposed to the seacoast environment after refurbishment and, also, to seawater immersion after splashdown, and during tow-back to CCAFS-Hangar AF refurbishment facilities. During refurbishment operations it was found that numerous TVC frames were experiencing internal corrosion and coating failures, both from salt air and seawater intrusions. Inspectors using borescopes would visually examine the internal cavities of the complicated aluminum alloy welded tubular structure. It was very difficult for inspectors to examine cavity corners and tubing intersections and particularly, to determine the extent of the corrosion and coating anomalies. Physical access to TVC frame internal cavities for corrosion removal and coating repair was virtually impossible, and an improved method using a Liquid (water based) Vapor-phase Corrosion Inhibitor (LVCI) for preventing initiation of new corrosion, and mitigating and/or stopping existing corrosion growth was recommended in lieu of hazardous paint solvents and high VOC / solvent based corrosion inhibitors. In addition, the borescopic inspection method used to detect corrosion, and/or coating anomalies had severe limitations because of part geometry, and an improved non-destructive inspection (NDI) method using Neutron Radiography (N-Ray) was also recommended.

Novak, Howard L.; Hall, Phillip B.

2003-01-01

328

Environmentally Compatible Vapor-Phase Corrosion Inhibitor for Space Shuttle Hardware  

NASA Technical Reports Server (NTRS)

USA-SRB Element is responsible for the assembly and refurbishment of the non-motor components of the SRB as part of Space Shuttle. Thrust Vector Control (TVC) frames structurally support components of the TVC system located in the aft skirt of the SRB (Solid Rocket Booster). TVC frames are exposed to the seacoast environment after refurbishment and, also, to seawater immersion after splashdown, and during tow-back to CCAFS-Hangar AF refurbishment facilities. During refurbishment operations it was found that numerous TVC frames were experiencing internal corrosion and coating failures, both from salt air and seawater intrusions. Inspectors using borescopes would visually examine the internal cavities of the complicated aluminum alloy welded tubular structure. It was very difficult for inspectors to examine cavity corners and tubing intersections and particularly. to determine the extent of the corrosion and coating anomalies. Physical access to TVC frame internal cavities for corrosion removal and coating repair was virtually impossible, and an improved method using a Liquid (water based) Vapor-phase Corrosion Inhibitor (LVCI) for preventing initiation of new corrosion, and mitigating and/or stopping existing corrosion growth was recommended in lieu of hazardous paint solvents and high VOC/solvent based corrosion inhibitors. In addition, the borescopic inspection method used to detect corrosion, and/or coating anomalies had severe limitations because of part geometry, and an improved non-destructive inspection (NDI) method using Neutron Radiography (N-Ray) was also recommended.

Novak, Howard L.; Hall, Phillip B.; Martin, David (Technical Monitor)

2002-01-01

329

Epitaxy of GaN on Si(111) substrate by the hydride vapor phase epitaxy method  

NASA Astrophysics Data System (ADS)

GaN epilayers were grown on Si(111) at 980 °C by a hydride vapor phase epitaxy (HVPE) method. AlxGa1-xN with thickness of ˜900 nm was inserted between Si substrate and GaN epilayer to act as a buffer layer. The investigation of the influence of different V/III ratios on GaN epilayer qualities reveals that high GaCl flow rate can increase the growth rate and improve the surface morphologies of GaN epilayers while high NH3 flow rate is not good for reducing dislocations in GaN epilayers, which can be proved from the analysis of X-ray diffraction rocking curve (XRC), cross-sectional image of scanning electron microscopy (SEM) and image of atomic force microscopy (AFM). Finally, 1.22 ?m GaN epilayer without cracks was successfully obtained with a three-step growth method. The surface roughness average (Ra) was measured to be 1.45 nm and the FWHM of GaN(0002) was 599 arcsec. The measured lattice constants for GaN epilayer were a=3.210 Å and c=5.177 Å, indicating the in-plane tensile stress and out-of-plane compressive stress of GaN epilayer.

Wang, Juan; Ryu, Heui-Bum; Park, Mi-Seon; Lee, Won-Jae; Choi, Young-Jun; Lee, Hae-Yong

2013-05-01

330

Exchange of Na+ and K+ between water vapor and feldspar phases at high temperature and low vapor pressure  

USGS Publications Warehouse

In order to determine whether gas (steam) containing a small amount of dissolved alkali chloride is effective in promoting base exchange of Na+ and K+ among alkali feldspars and coexisting brine or brine plus solid salt, experiments were carried out at 400-700??C and steam densities ranging down to less than 0.05. For bulk compositions rich in potassium, the low pressure results are close to previous high-pressure results in composition of the fluid and coexisting solid phase. However, when the bulk composition is more sodic, alkali feldspars are relatively richer in potassium at low pressure than at high pressure. This behaviour corresponds to enrichment of potassium in the gas phase relative to coexisting brine and precipitation of solid NaCl when the brine plus gas composition becomes moderately sodic. The gas phase is very effective in promoting base exchange between coexisting alkali feldspars at high temperature and low water pressure. This suggests that those igneous rocks which contain coexisting alkali feldspars out of chemical equilibrium either remained very dry during the high-temperature part of their cooling history or that the pore fluid was a gas containing very little potassium relative to sodium. ?? 1976.

Fournier, R. O.

1976-01-01

331

Selective transport of hydrocarbons in the unsaturated zone due to aqueous and vapor phase partitioning  

Microsoft Academic Search

Long-term ground water contamination can result from vapors and solutes emanating from organic liquids spilled in the unsaturated zone. The mathematical modeling analysis presented in this paper demonstrates for gasoline-range hydrocarbons, and other volatile organics commonly spilled, that diffusive transport in the unsaturated zone in a significant transport mechanism which can cause aqueous and vapor plumes to spread away from

Arthur L. Baehr

1987-01-01

332

Hybrid-phase growth in microcrystalline silicon thin films deposited by plasma enhanced chemical vapor deposition at low temperatures  

NASA Astrophysics Data System (ADS)

Crystallographic studies on microcrystalline silicon (?c-Si) films, which were prepared by very-high-frequency plasma-enhanced chemical vapor deposition at a low temperature of 180 °C, have been performed employing thickness evolutions of x-ray and electron diffraction measurements. The experimental results revealed that amorphous phase in ?c-Si is transited to crystalline phase in solid phase in whole region from the top to the bottom, and the transition to the (220) orientation is dominantly found. These growth phenomena are interpreted in terms of a proposed model, i.e., the hybrid-phase growth model consisting of conventional vapor-phase growth at the surface plus the solid-phase crystallization occurring in the film. Moreover, the hybrid-phase growth, particularly solid-phase crystallization at low temperatures, is discussed in conjunction with the further results on the thickness evolutions associated with ?c-Si films deposited on various underlayers or at substrate temperatures of 160-350 °C, or at SiH4 concentrations of 3%-5%.

Sugano, T.; Kitagawa, T.; Sobajima, Y.; Toyama, T.; Okamoto, H.

2005-05-01

333

Nano-architectural silica thin films with two-dimensionally connected cagelike pores synthesized from vapor phase.  

PubMed

Novel mesostructured silica thin films were prepared on a Si substrate by a vapor-phase synthesis. Vapor of tetraethoxysilane (TEOS) was infiltrated into a surfactant film consisting of a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer. Nanophase transition from a lamellar structure to a two-dimensional cage structure of a silica-surfactant nanocomposite was found under vapor infiltration. The rearrangement into the cage structure implies high mobility of the silica-surfactant composites in solid phase. The silica thin films have two-dimensionally connected cagelike mesopores and are isotropic parallel to the film surface. The structure of pores of the films is advantageous for next-generation low-k films. The mesoporous structure has a large lattice parameter d of approximately 102 A, silica layer thickness of approximately 58 A, pillar diameter in the middle of approximately 60 A, pore size of approximately 72 A, BET surface area of approximately 729 m(2)/g, and pore volume of approximately 1.19 cm(3)/g. The films synthesized by the vapor infiltration show a lower concentration of residual Si-OH groups compared to the films prepared by a conventional sol-gel method. The films show high thermal stability up to 900 degrees C and high hydrothermal stability. This method is a simpler process than conventional sol-gel techniques and attractive for mass production of a variety of organic-inorganic composite materials and inorganic porous films. PMID:15080689

Tanaka, Shunsuke; Nishiyama, Norikazu; Oku, Yoshiaki; Egashira, Yasuyuki; Ueyama, Korekazu

2004-04-21

334

Influence Nonuniformity of the Atmospheric Water Vapor Field on the Phase Measurements of Radio Signals from Global Navigation Satellite Systems  

NASA Astrophysics Data System (ADS)

We present the experimental results for the horizontal gradients of integrated content of atmospheric water vapor, which are retrieved from the phase measurements of signals in the receiver network of the global navigation satellite systems in 2011 in the Republic of Tatarstan. The seasonal gradient variation is found. The meridional gradient usually shows a decrease in integrated water vapor with increasing latitude, and its monthly mean values are equal to -1.8 mm and 0.1 mm of precipitable water per 100 km in August and December, respectively. The zonal monthly average gradient is somewhat smaller in magnitude than the meridional one and is equal 0.1 mm and -0.8 mm per 100 km in March/June and May/October, respectively. Instantaneous values of the gradients can by an order of magnitude higher than the monthly mean values. Contribution from the gradient of integral water vapor to the phase-measurement difference between two antennas spaced 30 km apart is shown to attain its maximum of 141.5 mm in August for the zenith angle 80°. Errors in determining the mutual location of the ground-based antennas of global navigation satellite systems due to the water vapor gradients can reach 66 mm and 16.9 mm in August and February, respectively.

Kalinnikov, V. V.; Khutorova, O. G.; Teptin, G. M.

2013-07-01

335

Immunomodulatory effects of cigarette smoke  

Microsoft Academic Search

Cigarette smoke is a major health risk factor which significantly increases the incidence of diseases including lung cancer and respiratory infections. This increased susceptibility may result from cigarette smoke-induced impairment of the immune system. While the acute effects of cigarette smoke on the immune system are less clear, chronic exposure to cigarette smoke or nicotine causes T cell unresponsiveness. This

Mohan L Sopori; Wieslaw Kozak

1998-01-01

336

Measurements of quantum noise in optical phase conjugation via four-wave mixing in an atomic vapor  

NASA Astrophysics Data System (ADS)

We present the results of a comprehensive investigation of the quantum-noise properties of a continuous-wave phase-conjugate mirror (PCM) formed using backward-four-wave mixing in potassium vapor. We characterize the quantum-noise properties of the PCM as functions of the vapor density, pump detuning from resonance, and relative frequency detuning of the signal beam from the probe beam. We compare the noise measurements of the PCM with the predicted noise of an ideal quantum-noise-limited PCM and determine the value of the minimum signal that can be used to perform phase conjugation with unity signal-to-noise ratio. For the range of vapor densities studied, we find that the PCM operates nearest the quantum-noise limit and that the value of the minimum signal is lowest under conditions in which the reflectivity is maximized. These results demonstrate that it is possible to perform phase conjugation with signals as weak as 14 fW with near-unity reflectivity. Our measurements are in qualitative agreement with the predictions of a quantum theory of phase conjugation via nearly degenerate four-wave mixing in a two-level system.

Lanzerotti, M. Y.; Schirmer, R. W.; Gaeta, Alexander L.; Agarwal, G. S.

1999-12-01

337

Quasi-equilibrium crystal shapes and kinetic Wulff plots for gallium nitride grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

In this paper we demonstrate work on developing the kinetic Wulff plots and quasi-equilibrium crystal shapes of GaN by hydride vapor phase epitaxy to understand the stable polar, semipolar, and nonpolar planes that emerge naturally from the GaN crystal. High quality bulk m-plane GaN substrates were masked with circular openings to perform selective area growth studies. Growths were performed by hydride vapor phase epitaxy over a range of temperatures, pressures and carrier gases. The quasi-equilibrium crystal shapes were shown to have clear m-plane {11¯00} facets and a sharp and flat (0001¯) N-face or c- face. The (0001) Ga-face or c+ face became faceted with {101¯1} planes emerging with reduced pressures and temperatures. Based on the stable facets, kinetic Wulff plots were constructed.

Bryant, Benjamin N.; Hirai, Asako; Young, Erin C.; Nakamura, Shuji; Speck, James S.

2013-04-01

338

Cigarette smoke induced changes in rat pulmonary clearance of /sup 99m/TcDTPA. A comparison of particulate and gas phases  

SciTech Connect

The rat model was developed to study the effects of cigarette smoke on pulmonary clearance of 99mTcDTPA. The method developed was sufficiently noninvasive to allow frequent repeat measurements to be made with a high degree of reproducibility. Animals exposed twice daily to 90 puffs of dilute whole cigarette smoke for 7 days showed an increase in /sup 99m/TcDTPA clearance from the lung which returned to normal within 3 wk of stopping exposure. Filtration of the smoke to remove all the particulate matter abolished the changes.

Minty, B.D.; Royston, D.

1985-12-01

339

Kinetic Modeling on the Adsorption of Vapor-Phase Mercury Chloride on Activated Carbon by Thermogravimetric Analysis  

Microsoft Academic Search

This study applied thermogravimetric analysis (TGA) technique to investigate the adsorption kinetics of vapor-phase mercury chloride (HgCl2) on activated carbon. HgCl2 is mainly emitted from the incineration of municipal solid waste (MSW) and causes severe adverse effects on human health and environment. Activated carbon injection (ACI) is the best available control technology for mercury removal from the flue gas of

Wei-Chin Chen; Hsun-Yu Lin; Chung-Shin Yuan; Chung-Hsuang Hung; John Koupal; Fred Minassian; Hannah Murray; Mani Natarajan; Fenfen Zhu; Masaki Takaoka; Kazuyuki Oshita; Shinsuke Morisawa; Hiroshi Tsuno; Yoshinori Kitajima; Wan-Fu Chiang; Hung-Yuan Fang; Chao-Hsiung Wu; Chang-Jun Huang; Ching-Yuan Chang; Yu-Min Chang; Ching-Liang Chen; Anders Nielsen; Lars Nielsen; Anders Feilberg; Knud Christensen; Yu-Yin Liu; Ta-Chang Lin; Ying-Jan Wang; Wei-Lun Ho; Janet Yanowitz; Robert McCormick; Lei Yu; Shichen Jia; Qinyi Shi; Tsang-Jung Chang; Hong-Ming Kao; Yu-Ting Wu; Wei-Hua Huang; Patrick Goodman; David Rich; Ariana Zeka; Luke Clancy; Douglas Dockery; Thomas Lavery; Christopher Rogers; Ralph Baumgardner; Kevin Mishoe; Li He; Guo Huang; Guangming Zeng; Hongwei Lu

2009-01-01

340

Transport characterization of GaAs quantum dots connected with quantum wires fabricated by selective area metalorganic vapor phase epitaxy  

Microsoft Academic Search

We fabricated novel quantum nanostructures where the quantum dots are connected with quantum wires using metalorganic vapor phase epitaxy (MOVPE) on (001) GaAs masked substrates. In particular a GaAs single electron transistor was successfully fabricated and its transport properties were investigated. We prepared two devices which have artificially designed two- or three-prominences in the channel region. These prominences produced a

K. Kumakura; J. Motohisa; T. Fukui

1998-01-01

341

Direct Growth of a-Plane GaN on r-Plane Sapphire Substrate by Metalorganic Vapor Phase Epitaxy  

Microsoft Academic Search

We have investigated the direct growth of nonpolar a-plane GaN layers on an r-plane sapphire substrate by metalorganic vapor-phase epitaxy (MOVPE). A high-density nucleation of GaN islands was obtained on the r-plane sapphire substrate at the initial stage of the high-temperature growth without a buffer layer, which resulted in a two-dimensional (2D) growth mode. We studied the effects of V\\/III

Masahiro Araki; Noriaki Mochimizo; Katsuyuki Hoshino; Kazuyuki Tadatomo

2007-01-01

342

M-Plane GaN Grown on m-Plane Sapphire by Hydride Vapor Phase Epitaxy  

Microsoft Academic Search

M-plane GaN epilayers have been directly grown on m-plane sapphire substrates by hydride vapor phase epitaxy using a low temperature GaN nucleation layer. The m-plane GaN surface is optically smooth and mirror-like, with rms roughness ˜2.0 nm (5× 5 mum2) measured by atomic force microscopy. We have found that the sapphire surface treatments prior to the growth determine the crystal

Tiankai Zhu; Denis Martin; Nicolas Grandjean

2009-01-01

343

Method of varying a characteristic of an optical vertical cavity structure formed by metalorganic vapor phase epitaxy  

DOEpatents

A process for forming an array of vertical cavity optical resonant structures wherein the structures in the array have different detection or emission wavelengths. The process uses selective area growth (SAG) in conjunction with annular masks of differing dimensions to control the thickness and chemical composition of the materials in the optical cavities in conjunction with a metalorganic vapor phase epitaxy (MOVPE) process to build these arrays.

Hou, Hong Q. (Albuquerque, NM); Coltrin, Michael E. (Albuquerque, NM); Choquette, Kent D. (Albuquerque, NM)

2001-01-01

344

Potential phase control of chromium oxide thin films prepared by laser-initiated organometallic chemical vapor deposition  

Microsoft Academic Search

We have used laser-initiated chemical vapor deposition to grow the chromium oxide thin films through the oxidation of Cr(CO)6 in an oxygen environment. While both Cr2O3 and CrO2 are present in the film, the relative weight of each phase depends on the oxygen partial pressure. The Curie temperature of the film increases and approaches the bulk TC of CrO2 (397

Ruihua Cheng; C. N. Borca; P. A. Dowben; Shane Stadler; Y. U. Idzerda

2001-01-01

345

Strain Variations with Sample Thickness in GaN Samples Grown by the Hydride Vapor Phase Epitaxy Method  

Microsoft Academic Search

Substantial progress in growing high quality GaN by the hydride vapor phase epitaxy (HVPE) method has been achieved(R. J. Molnar, W. Götz, L. T. Romano, and M. M. Johnson, J. Crystal Growth, 78), 147 (1997). High growth rates make the growth of thick layers practical. The epilayers are grown on sapphire substrates. GaN crystallizes in the wurtzite symmetry, and the

D. C. Look; D. C. Reynolds; B. Jogai; J. E. Hoelscher; R. E. Sherriff; R. J. Molnar

2000-01-01

346

Distribution of particulate- and vapor-phase n-alkanes and polycyclic aromatic hydrocarbons in urban atmosphere of Guangzhou, China  

Microsoft Academic Search

Polycyclic aromatic hydrocarbons (PAHs) are becoming a major component of atmospheric toxic pollutants (ATPs) in Guangzhou city, China. Studies showed that ATPs may have adverse health effect in urban area. An investigation on particulate- and vapor-phase distribution of n-alkanes and PAHs in urban atmosphere has been conducted. In LiWan district, 24h sampling for three consecutive days was performed in April

Xinhui Bi; Guoying Sheng; Ping’an Peng; Yingjun Chen; Zhiqiang Zhang; Jiamo Fu

2003-01-01

347

Advanced Life Support Water Recycling Technologies Case Studies: Vapor Phase Catalytic Ammonia Removal and Direct Osmotic Concentration  

NASA Technical Reports Server (NTRS)

Design for microgravity has traditionally not been well integrated early on into the development of advanced life support (ALS) technologies. NASA currently has a many ALS technologies that are currently being developed to high technology readiness levels but have not been formally evaluated for microgravity compatibility. Two examples of such technologies are the Vapor Phase Catalytic Ammonia Removal Technology and the Direct Osmotic Concentration Technology. This presentation will cover the design of theses two systems and will identify potential microgravity issues.

Flynn, Michael

2004-01-01

348

Using of sonochemically prepared components for vapor phase growing of SbI 3·3S 8  

Microsoft Academic Search

The using of sonochemically prepared components for growth of SbI3·3S8 single crystals from the vapor phase is presented for the first time. The good optical quality of the obtained crystals is important because this material is valuable for optoelectronics due to its non-linear optical properties. The products were characterized by using techniques such as X-ray crystallography, powder X-ray diffraction, scanning

M. Nowak; M. Kotyczka-Mora?ska; P. Szperlich; ?. Bober; M. Jesionek; M. K?pi?ska; D. Stró?; J. Kusz; J. Szala; G. Moskal; T. Rzycho?; J. M?y?czak; K. Kopczy?ski

2010-01-01

349

Formation of Single-Magnetic-Domain Iron Particles via Vapor-Phase Nucleation: Implications for the Solar Nebula  

Microsoft Academic Search

We report experimental evidence of the production of single-magnetic-domain iron grains via vapor-phase nucleation even in the absence of an ambient magnetic field. These single domain grains are thermodynamically stable as fully saturated magnetic dipoles. The spontaneous formation of fully magnetized single-domain iron grains, and by inference a variety of other single-domain particles such as taenite or magnetite, could greatly

Paul A. Withey; Joseph A. Nuth

1999-01-01

350

Metalorganic vapor phase epitaxial growth for buried heterostructure GaAlAs lasers with semi-insulating blocking layers  

Microsoft Academic Search

A two-step metalorganic vapor phase epitaxial growth technique for fully planar GaAs\\/GaAlAs single quantum well buried heterostructure lasers with oxygen-doped semi-insulating blocking layers is described. GaAlAs blocking layer with resistivity above 106 ? cm is reproducibly obtained by introducing oxygen at a concentration above 0.03 ppm during the growth. The selective growth mode of GaAlAs layers in etched grooves is

Masanobu Okayasu; Atsuo Kozen; Yuji Hasumi; Jiro Temmyo; Shingo Uehara

1987-01-01

351

Dual wavelength InGaN\\/GaN multi-quantum well LEDs grown by metalorganic vapor phase epitaxy  

Microsoft Academic Search

InGaN\\/GaN multiple quantum well (MQW) light-emitting diodes (LEDs) with different well widths and barrier widths were grown on sapphire substrates using metalorganic vapor phase epitaxy (MOVPE). The designed emission wavelengths were in the blue and green regions. The blue MQWs and green MQWs were deposited sequentially and the growth parameters were separately optimized for single color blue and green emission

Y. D. Qi; H. Liang; W. Tang; Z. D. Lu; Kei May Lau

2004-01-01

352

Engineering of compound semiconductor nanostructures by metalorganic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

The structure and chemistry of compound semiconductor surfaces during metalorganic vapor-phase epitaxy have been investigated. In particular, surface roughness, interface structure, and heterogeneous reaction kinetics of the group V precursors were studied. Moreover, the structures of the compound semiconductor surfaces have been examined using scanning tunneling microscopy, x-ray photoemission spectroscopy, and reflectance difference spectroscopy. The surface roughness of gallium arsenide (001) films changes with the temperature and growth rate. Height-height correlation analysis of scanning tunneling micrographs reveals that the root-mean height difference on the surface follows a power law dependence on lateral separation, i.e., Gamma(L) = kLalpha, up to a critical distance, Lc, after which it remains constant. For layer-by-layer growth, the roughness exponent, alpha, equals 0.25 +/- 0.05, whereas the critical distance increases from 50 to 150 nm as the substrate temperature increases from 825 to 900 K. The roughness exponent jumps to 0.65 +/- 0.1 upon transitioning to three-dimensional island growth. By relating the height-height correlation function to the Einstein diffusivity relationship, the activation energy for gallium surface diffusion was estimated: Ed = 1.35 +/- 0.1 eV. Exposing indium phosphide films to 10 mTorr of tertiarybutylarsine below 500°C results in the deposition of a thin indium arsenide layer from 1.5 to 5.0 atomic layers thick (2.3 to 7.5 A). The surface of this layer remains atomically smooth independent of arsenic exposure time. However, in an overpressure of tertiarybutylarsine at or above 500°C, the arsenic atoms diffuse into the bulk, creating strained InAsP films. These films form three-dimensional island structures to relieve the built-up strain. The activation energy and pre-exponential factor for arsenic diffusion into indium phosphide was found to be: Ed = 1.7 +/- 0.2 eV and Do = 2.3 +/- 1.0 x 10-7 cm2/s. The kinetics of phosphine adsorption and phosphorus desorption from gallium phosphide and indium phosphide (001) surfaces have been studied using reflectance difference spectroscopy to monitor the phosphorus coverage in real time. The adsorption and desorption processes follow first-order reactions. The rate parameters were determined by fitting the experimental data to a kinetic model. The initial sticking coefficients of phosphine on GaP (2x4), (1x1), and InP (2x4) surfaces were found to be 730.0·exp(-0.6 +/- 0.2(eV)/kT), 1.6·exp(-0.4 +/- 0.2(eV)/kT) and 0.0055·exp(-0.1 +/- 0.2eV/kT), respectively. The desorption of phosphorus from the GaP (2x1) and (1x1) surfaces was first-order in coverage with rate constants of 5.0 x 1015(s-1)·exp(-2.6 +/- 0.2(eV)/kT) and 5.0 x 1015(s-1 )·exp(-2.9 +/- 0.4(eV)/kT). The results presented in this thesis illustrate how molecular-scale chemical phenomena affect the evolution of compound semiconductor nanostructures during metalorganic vapor-phase epitaxy.

Law, Daniel Ching Bong

353

An Evaluation of the Vapor Phase Catalytic Ammonia Removal Process for Use in a Mars Transit Vehicle  

NASA Technical Reports Server (NTRS)

An experimental program has been developed to evaluate the potential of the Vapor Phase Catalytic Ammonia Reduction (VPCAR) technology for use as a Mars Transit Vehicle water purification system. Design modifications which will be required to ensure proper operation of the VPCAR system in reduced gravity are also evaluated. The VPCAR system is an integrated wastewater treatment technology that combines a distillation process with high temperature catalytic oxidation. The distillation portion of the system utilizes a vapor compression distillation process to provide an energy efficient phase change separation. This portion of the system removes any inorganic salts and large molecular weight, organic contaminates, i.e., non-volatile, from the product water stream and concentrates these contaminates into a byproduct stream. To oxidize the volatile organic compounds and ammonia, a vapor phase, high temperature catalytic oxidizer is used. This catalytic system converts these compounds along with the aqueous product into CO2, H2O, and N2O. A secondary catalytic bed can then be used to reduce the N2O to nitrogen and oxygen (although not evaluated in this study). This paper describes the design specification of the VPCAR process, the relative benefits of its utilization in a Mars Transit Vehicle, and the design modification which will be required to ensure its proper operation in reduced gravity. In addition, the results of an experimental evaluation of the processors is presented. This evaluation presents the processors performance based upon product water purity, water recovery rates, and power.

Flynn, Michael; Borchers, Bruce

1998-01-01

354

Characterization of vapor phase mercury released from concrete processing with baghouse filter dust added cement.  

PubMed

The fate of mercury (Hg) in cement processing and products has drawn intense attention due to its contribution to the ambient emission inventory. Feeding Hg-loaded coal fly ash to the cement kiln introduces additional Hg into the kiln's baghouse filter dust (BFD), and the practice of replacing 5% of cement with the Hg-loaded BFD by cement plants has recently raised environmental and occupational health concerns. The objective of this study was to determine Hg concentration and speciation in BFD as well as to investigate the release of vapor phase Hg from storing and processing BFD-added cement. The results showed that Hg content in the BFD from different seasons ranged from 0.91-1.44 mg/kg (ppm), with 62-73% as soluble inorganic Hg, while Hg in the other concrete constituents were 1-3 orders of magnitude lower than the BFD. Up to 21% of Hg loss was observed in the time-series study while storing the BFD in the open environment by the end of the seventh day. Real-time monitoring in the bench system indicated that high temperature and moisture can facilitate Hg release at the early stage. Ontario Hydro (OH) traps showed that total Hg emission from BFD is dictated by the air exchange surface area. In the bench simulation of concrete processing, only 0.4-0.5% of Hg escaped from mixing and curing BFD-added cement. A follow-up headspace study did not detect Hg release in the following 7 days. In summary, replacing 5% of cement with the BFD investigated in this study has minimal occupational health concerns for concrete workers, and proper storing and mixing of BFD with cement can minimize Hg emission burden for the cement plant. PMID:24444016

Wang, Jun; Hayes, Josh; Wu, Chang-Yu; Townsend, Timothy; Schert, John; Vinson, Tim; Deliz, Katherine; Bonzongo, Jean-Claude

2014-02-18

355

Identification of novel illicit amphetamines from vapor-phase FTIR spectra - a chemometrical solution.  

PubMed

A computer-aided procedure automating the identification of illicit amphetamine analogs eluting from a gas chromatograph coupled to a Fourier transform infrared spectrometer is presented. The expert system discriminates novel amphetamines from other classes of drugs of abuse normally screened in illicit tablets or powders. The main analytical advantages of the system over the automated procedures dedicated to general unknown analysis are the objectivity and the accuracy in predicting the class identity of the compound (i.e. stimulant, hallucinogen) when the reference spectrum is not present in the spectral library. The expert system uses quantitative thresholds defining the similarity of the unknown to the classes of illicit amphetamines and checks the presence of the molecular skeletons associated with different psychotropic effects of amphetamines. The challenge in building the system was the fuzziness of vapor-phase Fourier transform infrared spectrometer spectra of low-weight molecules such as amphetamines. This paper emphasizes the chemometrical techniques found most appropriate for modeling such spectral behavior. An exploratory (principal component) analysis indicated the sample preparation and the feature weight function yielding the best input for the knowledge base. The class identity of a compound was assigned using Soft Independent Modeling of Class Analogy. A rule-based decision system was implemented to enhance the accuracy in identity assignment. The flow diagram optimizing the knowledge base content of each model is presented. Finally, up to 81.13% (out of 159 tested compounds) were classified with a 5% confidence level. The total correct classification rate was 93.93%, for a yield of 96.30% true positive amphetamines. PMID:18968101

Praisler, M; Dirinck, I; Van Bocxlaer, J; De Leenheer, A; Massart, D L

2000-10-01

356

Investigation of vapor-phase lubrication in a gas turbine engine  

SciTech Connect

The liquid oil lubrication system of current aircraft jet engines accounts for approximately 10--15% of the total weight of the engine. It has long been a goal of the aircraft gas turbine industry to reduce this weight. Vapor-Phase Lubrication (VPL) is a promising technology to eliminate liquid oil lubrication. The current investigation resulted in the first gas turbine to operate in the absence of conventional liquid lubrication. A phosphate ester, commercially known as DURAD 620B, was chosen for the test. Extensive research at Wright Laboratory demonstrated that this lubricant could reliably lubricate rolling element bearings in the gas turbine engine environment. The Allison T63 engine was selected as the test vehicle because of its small size and bearing configuration. Specifically, VPL was evaluated in the number eight bearing because it is located in a relatively hot environment, in line with the combustor discharge, and it can be isolated from the other bearings and the liquid lubrication system. The bearing was fully instrumented and its performance with standard oil lubrication was documented. Results of this baseline study were used to develop a thermodynamic model to predict the bearing temperature with VPL. The engine was then operated at a ground idle condition with VPL with the lubricant misted into the No. 8 bearing at 13 ml/h. The bearing temperature stabilized at 283 C within 10 minutes. Engine operation was continued successfully for a total of one hour. No abnormal wear of the rolling contact surfaces was found when the bearing was later examined. Bearing temperatures after engine shutdown indicated the bearing had reached thermodynamic equilibrium with its surroundings during the test.

Van Treuren, K.W.; Barlow, D.N.; Heiser, W.H. [Air Force Academy, Colorado Springs, CO (United States). Dept. of Aeronautics; Wagner, M.J.; Forster, N.H. [Aero Propulsion and Power Directorate, Wright-Patterson AFB, OH (United States). Fuels and Lubrication Div.

1998-04-01

357

In situ cleaning of GaN(0001) surfaces in a metalorganic vapor phase epitaxy environment  

NASA Astrophysics Data System (ADS)

The presence of ammonia in a metalorganic vapor phase epitaxy (MOVPE) system configured for the growth of GaN films is necessary and sufficient to remove adsorbed O- and C-containing species from the (0001) surface of this compound without measurable decomposition of this surface. Chemical and microstructural evidence in support of this statement has been obtained from investigations concerned with the extension of a previously developed in situ process route for cleaning heated GaN(0001) surfaces in a molecular beam epitaxy environment using flowing ammonia to the higher pressure regime of MOVPE. Thin films of GaN were deposited under 20 Torr total pressure on GaN templates, previously exposed to the laboratory ambient, and heated in either a nitrogen/hydrogen or an ammonia/hydrogen mixture to the deposition temperature of 1020 °C. Secondary ion mass spectroscopy of these samples revealed significant concentrations of carbon and oxygen at the GaN/GaN interface in the former and the absence of these contaminants above the detection limits of the instrument in the latter. The surfaces of the templates heated in the nitrogen/hydrogen atmosphere also decomposed sufficiently to form a very thin liquid Ga layer that reacted with ammonia to form a GaN-containing film either at the outset of film growth or on cooling in an ammonia/nitrogen atmosphere. Atomic force microscopy (AFM) showed a smoother surface for the GaN films deposited on templates heated and cleaned in the ammonia/hydrogen mixture relative to films deposited on templates heated in the nitrogen/hydrogen mixture. The latter surface contained both a higher density of step terminations, indicative of a higher density of threading dislocations having screw and mixed character, and pits.

Reitmeier, Z. J.; Park, J.-S.; Mecouch, W. J.; Davis, R. F.

2004-09-01

358

TREATMENT OF PRODUCED WATERS USING A SURFACTANT MODIFIED ZEOLITE/VAPOR PHASE BIOREACTOR SYSTEM  

SciTech Connect

Co-produced water from the oil and gas industry accounts for a significant waste stream in the United States. It is by some estimates the largest single waste stream in the country, aside from nonhazardous industrial wastes. Characteristics of produced water include high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component, and chemicals added during the oil-production process. While most of the produced water is disposed via reinjection, some of them must be treated to remove organic constituents before the water is discharged. Current treatment options are successful in reducing the organic content; however, they cannot always meet the levels of current or proposed regulations for discharged water. Therefore, an efficient, cost-effective treatment technology is needed. Surfactant-modified zeolite (SMZ) has been used successfully to treat contaminated ground water for organic and inorganic constituents. In addition, the low cost of natural zeolites makes their use attractive in water-treatment applications. Our previous DOE research work (DE-AC26-99BC15221) demonstrated that SMZ could successfully remove BTEX compounds from the produced water. In addition, SMZ could be regenerated through a simple air sparging process. The primary goal of this project is to develop a robust SMZ/VPB treatment system to efficiently remove the organic constituents from produced water in a cost-effective manner. This report summarizes work of this project from October 2002 to March 2003. In this starting stage of this study, we have continued our investigation of SMZ regeneration from our previous DOE project. Two saturation/stripping cycles have been completed for SMZ columns saturated with BTEX compounds. Preliminary results suggest that BTEX sorption actually increases with the number of saturation/regeneration cycles. Furthermore, the experimental vapor phase bioreactors for this project have been designed and are currently being assembled to treat the off-gas from the SMZ regeneration process.

Lynn E. Katz; Kerry A. Kinney; R.S. Bowman; E.J. Sullivan

2003-04-01

359

High Temperature Electrolysis of Water Vapor: Hot Elly, Phase 2A.  

National Technical Information Service (NTIS)

The systematic continuation of the basic developments for the high temperature electrolysis of water vapor with respect to a technical realization of the process are described. The optimization of the electrolyte geometry and of the materials for the inte...

W. Doenitz E. Erdle H. Hermeking A. Koch W. Kock

1984-01-01

360

Investigation of Subterranean Fuel Vapor Extraction and Destruction Using a Diesel Engine: Phase 2.  

National Technical Information Service (NTIS)

This project aims to remediate fuel spills by extracting hydrocarbon vapors from contaminated earth, and burning them in a diesel engine. The diesel engine destroys hydrocarbons more effectively than spark-ignited units currently in use, uses less fuel, a...

M. E. Schulman K. E. Stoecklein

2003-01-01

361

Mathematical Model for Determining Rate of Kill of Microbial Aerosols by Vapor-Phase Disinfectants.  

National Technical Information Service (NTIS)

A method for screening chemical vapors for decontaminating microbial aerosols was developed by applying Raoult's law. The method included a simple small-scale aerosol chamber system that was conveniently and rapidly operated by one person. The vegetative ...

J. B. Harstad

1981-01-01

362

VAPOR PHASE MERCURY SORPTION BY ORGANIC SULFIDE MODIFIED BIMETALLIC IRON-COPPER NANOPARTICLE AGGREGATES  

EPA Science Inventory

Novel organic sulfide modified bimetallic iron-copper nanoparticle aggregate sorbent materials have been synthesized for removing elemental mercury from vapor streams at elevated temperatures (120-140 °C). Silane based (disulfide silane and tetrasulfide silane) and alkyl sulfide ...

363

NOVEL CERAMIC-ORGANIC VAPOR PERMEATION MEMBRANES FOR VOC REMOVAL - PHASE I  

EPA Science Inventory

Vapor permeation holds much promise for becoming a highly efficient means of preventing VOC emissions that are now generated by a variety of stationary sources, including solvent and surface coating operations, gasoline storage operations, and printing operations. A limitation of...

364

NOVEL CERAMIC-ORGANIC VAPOR PERMEATION MEMBRANES FOR VOC REMOVAL - PHASE II  

EPA Science Inventory

Vapor permeation with highly permeable and organic-selective membranes is becoming an increasingly popular technique for preventing VOC emissions that are generated by a variety of stationary sources, including solvent and surface coating operations, gasoline storage operat...

365

Role of Impact-Induced, Vapor-Phase Deposition in the Lunar Regolith Formation: Clues from the New Mineral, Hapkeite  

NASA Astrophysics Data System (ADS)

To correctly interpret the spectral properties of airless planetary bodies such as the Moon, Vesta, etc., it is important to understand the complex space-weathering processes responsible for their soil formation. In the absence of water and atmosphere, micrometeorite impacts play the dominant role in soil development on such airless bodies. Kinetics of such transient impacts can result in ultra-high-temperature events and cause melting and vaporization of even less-volatile elements in the soil. A regolith-breccia clast in lunar meteorite Dh-280 contains small (e.g. 10-20? m) opaque mineral grains consisting of three distinct new lunar mineral phases- FeSi, Fe2Si, FeSi2 [Anand et al., 2002, 2003, LPSC]. We have named the Fe2Si mineral, HAPKEITE, in honor of Prof. Bruce Hapke. We are using a new X-ray microdiffraction technique with beamline 7.3.3 of ALS to refine and determine the crystal structures of these Fe-Si phases. Preliminary results indicate the possibility of superlattice structures in some cases. The presence of Fe-Si phases in a lunar soil fragment in Dh-280 indicates extreme reducing conditions. The two most plausible reduction mechanisms include impact-induced a) melting, evaporation, and vapor deposition and b) solar-wind hydrogen reduction. Our preferred scenario for the formation of these phases involves the melting and vaporization of lunar soil by micrometeorite impact. The transient, ultra-high-temperature impact could cause vaporization and thermal dissociation of FeO and SiO2 into their constituent atoms. The ubiquitous presence of np-Fe in silica-rich glass on the surface of most mature, lunar-soil grains has already been confirmed (Keller & McKay, 1993, Science). We propose that with further dissociation, the Si in the vapor phase could readily combine, in various proportions, with Fe, and condense as Fe-Si grains. These observations necessitate further careful investigation of lunar soils for the presence of Fe-Si phases, as these can significantly contribute towards the spectral reflectance of lunar soils, the actual material observed remotely.

Anand, M.; Taylor, L.; Nazarov, M.; Shu, J.; Mao, H.; Hemley, R.

2003-12-01

366

Cigarette Ads and Youth.  

ERIC Educational Resources Information Center

Points out ways the tobacco industry markets products to youth, including paid advertisements, sponsorship of sporting events, music concerts, and magazines. Relates several focal points for smoking prevention, which include deglamorization of cigarette advertisements and making smoking socially undesirable. (LS)

Carol, Julia

1988-01-01

367

Analyzing Cigarette Smoke.  

ERIC Educational Resources Information Center

Details an activity in which students use their natural inquisitiveness about their personal environment to investigate the composition of cigarette smoke. Includes techniques for measuring tar and carbon monoxide content. (DDR)

Jaffe, Dan; Griffin, Dale; Ricker, Janet

1997-01-01

368

E-Cigarettes  

MedlinePLUS

... re not because e-cigarettes are still putting nicotine — a highly addictive drug — into the body. Electronic ... use cartridges filled with a liquid that contains nicotine, flavorings, and other chemicals. A heating device in ...

369

Molecular association of heteronuclear vibrating square-well dumbbells in liquid-vapor phase equilibrium.  

PubMed

Molecular aggregates are formed by heteronuclear vibrating square-well dumbbells. In a recent article [G. A. Chapela and J. Alejandre, J. Chem. Phys., 132(10), 104704 (2010)], it is shown that heteronuclear vibrating square-well dumbbells with a diameter ratio between particles of 1/2 and interacting potential ratio of 4 form micelles of different sizes and shapes which manifest themselves in both the liquid and vapor phases, up to and above the critical point. This means that micellization and phase separation are present simultaneously in this simple model. These systems present a maximum in the critical temperature when plotted against the potential well depth of the second particle ?(2). In the same publication, it was speculated that the formation of micelles was responsible for the appearance of the maximum. A thorough study on this phenomena is presented here and it is found that there is a threshold on the size of the second particle and its corresponding depth of interaction potential, where the micelles are formed. If the diameter and well depth of the second particle are small enough for the first and deep enough for the second, micelles are formed. For ?(2)/?(1) between 0.25 and 0.65 and ?(2)/?(1) larger than 5.7, micelles are formed up to and above the critical temperature. Outside these ranges micelles appear only at temperatures lower than the critical point. There is a strong temperature dependence on the formation and persistence of the aggregates. For the deepest wells and large enough second particles, a gel interconnected aggregate is obtained. In this work, the micelles are formed at temperatures as low as the triple point and as high as the critical point and, in some cases, persist well above it. The presence of these maxima in critical temperatures T(c) when plotted against ?(2) as follows. At lower values of ?(2), an increase of T(c) is obtained as is expected by the increase of the attractive volume as indicated by the principle of corresponding states. As ?(2) increases further, the formation of molecular aggregates produce a saturation effect of the deepening of the potential well by encapsulating the particles of the second kind inside the micelles, so the resulting T(c) represents a new poly disperse system of molecular aggregates and not the original heteronuclear vibrating square-well dumbbells. The surface tension is also analyzed for these systems, and it is shown that decreases with increasing attraction due to the formation of molecular aggregates. PMID:21682505

Chapela, Gustavo A; de Río, Fernando; Alejandre, José

2011-06-14

370

A Method to Use Modis Water Vapor Products For Correction of Atmospheric-Induced Phase in Interferogram  

NASA Astrophysics Data System (ADS)

DInSAR is a major space-geodetic technique widely used in the study of earth surface deformation. A major source of phase errors in DInSAR technique is heterogeneous phase delay caused mainly by variation of water vapors in troposphere, which is a factor limiting applications of DInSAR mainly to arid areas. This paper presents study results of three methods to correct atmospheric phase errors in DInSAR interferograms formed by TerraSAR-X images. The first method is the use of wet delay derived directly from MODIS precipitable water vapor product. The second method employs ground-based meteorological data to calibrate MODIS PWV before computing phase delays. The third method improves the second method by estimating the expected MODIS PWV value at the time of the TerraSAR-X image acquisitions which over the Bangkok test area is 5 hour earlier than that of MODIS. The time-shifted linear fit model along with the IDW interpolation is used to estimate more realistic phase delays over entire imaging area. From the study of this tropical test area, this time-corrected method provides best results while the second method also achieves a significantly better result than those obtained from direct use of MODIS PWV data.

Keeratikasikorn, Chaiyapon; Trisirisatayawong, Itthi

2011-01-01

371

Sol-gel synthesis of MCM-41 silicas and selective vapor-phase modification of their surface  

NASA Astrophysics Data System (ADS)

Silica particles with uniform hexagonal mesopore architecture were synthesized by template directed sol-gel condensation of tetraethoxysilane or mixture of tetraethoxysilane and (3-chloropropyl)triethoxysilane in a water-ethanol-ammonia solution. Selective functionalization of exterior surface of parent materials was carried out by postsynthetic treatment of template-filled MCM-41 and Cl-MCM-41 with vapors of (3-chloropropyl)triethoxysilane and 1,2-ethylenediamine in vacuum. The chemical composition of obtained mesoporous silicas was estimated by IR spectroscopy and chemical analysis of surface products of reactions. Characteristics of porous structure of resulting materials were determined from the data of X-ray, low-temperature nitrogen ad-desorption and transmission electron microscopy measurements. Obtained results confirm invariability of highly ordered mesoporous structure of MCM-41 and Cl-MCM-41 after their selective postsynthetic modification in vapor phase. It was proved that proposed method of vapor-phase functionalization of template-filled starting materials is not accompanied by dissolution of the template and chemical modification of pores surface. This provides preferential localization of grafted functional groups onto the exterior surface of mesoporous silicas.

Roik, N. V.; Belyakova, L. A.

2013-11-01

372

The role of ion/surface interactions and photo-induced reactions during film growth from the vapor phase  

NASA Astrophysics Data System (ADS)

Recent progress in the understanding of mechanisms associated with low-energy (often < 100 eV) ion/surface interactions and photo-induced reactions during vapor-phase crystal growth are reviewed. Ion/surface interactions play an important role in a variety of deposition technologies including sputtering, plasma-assisted chemical vapor deposition, and, more recently, molecular beam epitaxy. Effects such as trapping, preferential sputtering, and collisional mixing are used to interpret and, in some cases, model experimental results concerning the effects of low-energy ion bombardment on nucleation and film growth kinetics, the evolution of film microstructure, elemental incorporation probabilities, surface segregation rates, and dopant depth distributions. The role of photo-stimulated gas-phase and surface reactions during laser-assisted chemical vapor deposition, including single, multiple, and multiphoton-initiated processes, radical production, and adlayer photochemistry, are also discussed together with newly developed laser-processing techniques during deposition. The focus of this review is on the development of an understanding of the controlling mechanisms in both ion/surface and photo-stimulated processes.

Greene, J. E.; Motooka, T.; Sundgren, J.-E.; Lubben, D.; Gorbatkin, S.; Barnett, S. A.

1987-06-01

373

Monomolecular layers and thin films of silane coupling agents by vapor-phase adsorption on oxidized aluminum  

SciTech Connect

Thin films of tetraethoxysilane [TEOS], (3-bromopropyl)trimethoxysilane [BPS], trimethoxyvinylsilane [VS], and 3-(trimethoxysilyl) propyl methacrylate [TPM] on oxidized aluminum surfaces have been investigated by reflection-absorption FTIR spectroscopy, ellipsometry, contact angle, and quartz crystal microbalance (QCM) measurements. Gravimetric measurements with the QCM can reveal quantitative aspects of adsorption and film formation, even for films as thin as monolayers. Adsorption of these silane coupling agents from solution typically produces multilayer films. Vapor-phase adsorption of TEOS and TPM at room temperature results in monomolecular layers. The coupling agents VS and BPS require additional heating after the vapor-phase adsorption to initiate the hydrolysis and condensation reactions necessary for the surface attachment, which produces one to three layers. For vapor adsorbed films a packing density of 4-7 molecules/nm{sup 2} was found. The data strongly suggest that the organic moieties in several of these films have a preferential orientation on the surface; they can be viewed as two-dimensional, oligomeric siloxane networks with oriented organic chains. Subsequent heating of TPM films results in structural rearrangements; heating of TEOS results in complete condensation to SiO{sub 2} films. 43 refs., 6 figs., 4 tabs.

Kurth, D.G.; Bein, T. [Purdue Univ., West Lafayette, IN (United States)

1992-08-06

374

Cigarette Smoke Components and Disease: Cigarette Smoke Is More Than a Triad of Tar, Nicotine, and Carbon Monoxide  

Microsoft Academic Search

INTRODUCTION Cigarette smoke is a complex mixture of chemicals. Some smoke components, such as carbon monoxide (CO), hydrogen cyanide (HCN), and nitrogen oxides, are gases. Others, such as formaldehyde, acrolein, benzene, and certain N-nitrosamines, are volatile chemicals contained in the liquid- vapor portion of the smoke aerosol. Still others, such as nicotine, phenol, polyaromatic hydrocarbons (PAHs), and certain tobacco-specific nitrosamines

Jeffrey E. Harris

375

Treatment of Produced Waters Using a Surfactant Modified Zeolite/Vapor Phase Bioreactor System  

SciTech Connect

This report summarizes work performed on this project from October 2004 through March 2005. In previous work, a surfactant modified zeolite (SMZ) was shown to be an effective system for removing BTEX contaminants from produced water. Additional work on this project demonstrated that a compost-based biofilter could biodegrade the BTEX contaminants found in the SMZ regeneration waste gas stream. However, it was also determined that the BTEX concentrations in the waste gas stream varied significantly during the regeneration period and the initial BTEX concentrations were too high for the biofilter to handle effectively. A series of experiments were conducted to determine the feasibility of using a passive adsorption column placed upstream of the biofilter to attenuate the peak gas-phase VOC concentrations delivered to the biofilter during the SMZ regeneration process. In preparation for the field test of the SMZ/VPB treatment system in New Mexico, a pilot-scale SMZ system was also designed and constructed during this reporting period. Finally, a cost and feasibility analysis was also completed. To investigate the merits of the passive buffering system during SMZ regeneration, two adsorbents, SMZ and granular activated carbon (GAC) were investigated in flow-through laboratory-scale columns to determine their capacity to handle steady and unsteady VOC feed conditions. When subjected to a toluene-contaminated air stream, the column containing SMZ reduced the peak inlet 1000 ppmv toluene concentration to 630 ppmv at a 10 second contact time. This level of buffering was insufficient to ensure complete removal in the downstream biofilter and the contact time was longer than desired. For this reason, using SMZ as a passive buffering system for the gas phase contaminants was not pursued further. In contrast to the SMZ results, GAC was found to be an effective adsorbent to handle the peak contaminant concentrations that occur early during the SMZ regeneration process. At a one second residence time, the GAC bed reduced peak contaminant concentrations by 97%. After the initial peak, the inlet VOC concentration in the SMZ regeneration gas stream drops exponentially with time. During this period, the contaminants on the GAC subsequently desorbed at a nearly steady rate over the next 45 hours resulting in a relatively steady effluent concentration of approximately 25 ppm{sub v}. This lower concentration is readily degradable by a downstream vapor phase biofilter (VPB) and the steady nature of the feed stream will prevent the biomass in the VPB from enduring starvation conditions between SMZ regeneration cycles. Repetitive sorption and desorption cycles that would be expected in the field were also investigated. It was determined that although the GAC initially lost some VOC sorption capacity, the adsorption and desorption profiles stabilized after approximately 6 cycles indicating that a GAC bed should be suitable for continuous operation. In preparation for the pilot field testing of the SMZ/VPB system, design, ''in-house'' construction and testing of the field system were completed during this project period. The design of the SMZ system for the pilot test was based on previous investigations by the PI's in Wyoming, 2002 and on analyses of the produced water at the field site in New Mexico. The field tests are scheduled for summer, 2005. A cost survey, feasibility of application and cost analyses were completed to investigate the long term effectiveness of the SMZ/VPB system as a method of treating produced water for re-use. Several factors were investigated, including: current costs to treat and dispose of produced water, end-use water quality requirements, and state and federal permitting requirements.

Soondong Kwon; Elaine B. Darby; Li-Jung Chen; Lynn E. Katz; Kerry A. Kinney; R. S. Bowman; E. J. Sullivan

2005-03-11

376

Deep-Ultraviolet Light-Emitting Diodes Fabricated on AlN Substrates Prepared by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) were fabricated on AlN substrates. The AlN substrates were prepared by growing thick hydride vapor phase epitaxy (HVPE)-AlN layers on bulk AlN substrates prepared by physical vapor transport (PVT). After growing an LED structure, the PVT-AlN substrates were removed by mechanical polishing. This process allowed the fabrication of DUV-LEDs on HVPE-AlN substrates with high crystalline quality and DUV optical transparency. The DUV-LEDs exhibited a single emission peaking at 268 nm through the HVPE-AlN substrates. The output power as high as 28 mW was obtained at an injection current of 250 mA.

Kinoshita, Toru; Hironaka, Keiichiro; Obata, Toshiyuki; Nagashima, Toru; Dalmau, Rafael; Schlesser, Raoul; Moody, Baxter; Xie, Jinqiao; Inoue, Shin-ichiro; Kumagai, Yoshinao; Koukitu, Akinori; Sitar, Zlatko

2012-12-01

377

Bragg and Laue x-ray diffraction study of dislocations in thick hydride vapor phase epitaxy GaN films  

NASA Astrophysics Data System (ADS)

The dislocation structure of hydride vapor phase epitaxial thick GaN layers grown on sapphire is studied by analysis of the microdistortion tensor components. Symmetrical reflections (including reflections from planes forming a large angle with the basal plane) with two modes of scanning (? and ?-2?) in two geometries (Bragg and Laue) are used to obtain the tensor components. The instant connections between the tensor components and major dislocation types are specified. Different types of dislocation distributions have been identified in the thick GaN films grown on sapphire with and without undoped and Si-doped metalorganic chemical vapor deposited templates. Transmission electron microscopy was used to confirm the x-ray results by direct visualization of defect rearrangements.

Ratnikov, V.; Kyutt, R.; Shubina, T.; Paskova, T.; Valcheva, E.; Monemar, B.

2000-12-01

378

Evaluating headspace component vapor-time profiles by solid-phase microextraction with external sampling of an internal standard.  

PubMed

The vapor-time profiles of explosive materials are of valuable interest to Homeland Security, providing critical information that can aid in the detection of explosive-containing devices. An approach is described that achieves reproducible characterization of volatile components as a function of time based on comparison of the sample response to an externally sampled internal standard (ESIS). Utilizing nonequilibrium solid-phase microextraction (SPME) measurements, this SPME-ESIS technique improves reproducibility (reported as percent relative standard deviation) of vapor-time profiles by approximately an order of magnitude and allows for an equitable comparison of the target compound between diverse materials. Two odorants associated with canine detection of explosives, 2-ethyl-1-hexanol and 2,4-dinitrotoluene, are used to optimize parameters for the SPME-ESIS technique. PMID:21961948

MacCrehan, William; Moore, Stephanie; Schantz, Michele

2011-11-15

379

Vapor pressures and gas-phase PVT data for 1-chloro-1,2,2,2-tetrafluoroethane (R124)  

SciTech Connect

We present new data for the vapor pressure and PVT surface of 1-chloro-1,2,2,2-tetrafluoroethane (designated R124 by the refrigeration industry) in the temperature range 278-423 K. The PVT data are for the gas phase at densities up to 1.5 times the critical density. Correlating equations are given for the vapor pressures from 220 K to the critical temperature, 395.43 K, and for the PVT surface at densities up to 2 mol [center dot] L[sup [minus]1] (approximately 0.5 times the critical density). Second and third virial coefficients have been derived from the PVT measurements. 16 refs., 4 figs., 6 tabs.

Boyes, S.J.; Weber, L.A. (National Inst. of Standards and Technology, Gaithersburg, MD (United States))

1994-05-01

380

Metalorganic vapor-phase epitaxy of indium phosphide and related materials  

NASA Astrophysics Data System (ADS)

The surface chemistry of indium phosphide and related compound semiconductors during metalorganic vapor-phase epitaxy (MOVPE) has been investigated. In particular, the group V precursor chemistry, indium phosphide (001) atomic structure and the InP oxidation process have been examined. The properties of the semiconductors were studied using infrared spectroscopy, molecular cluster calculations, x-ray photoelectron spectroscopy, reflectance difference spectroscopy, x-ray diffraction, and photoluminescence spectroscopy. Indium phosphide, gallium arsenide phosphide, and aluminum indium phosphide have been deposited by MOVPE using tertiarybutylphosphine and tertiarybutylarsine. Minimum incorporation in InP was observed at 565°C and a V/III ratio of 32. In this case, the material contained a background carrier concentration of 2.7 x 1014 cm-3, and the Hall mobilities were 4,970 and 135,000 cm2/V·s at 300 and 77 K. The oxygen contamination in AlInP was found to be only 9.0 x 10 15 cm-3 for deposition at 650°C and a V/III ratio of 35. The relative distribution of arsenic to phosphorus in GaAs yP1-y was determined at temperatures between 525 and 575°C. The distribution coefficient [(NAs/ NP)film/(PTBAs /PTBP)gas] ranged from 25.4 to 8.4, and exhibited an Arrhenius relationship with an apparent activation energy of 1.2 eV. The surface structure of the indium phosphide (001)-(2 x 1) reconstruction has been clarified in this thesis. Infrared spectra collected during atomic deuterium titration of the (2 x 1) surface revealed a sharp P-H stretching mode at 2308 cm-1. Based on theoretical cluster calculations using density functional theory, this mode was due to a single hydrogen atom bonded to one end of a buckled phosphorus dimer. These results confirmed that the (2 x 1) structure was stabilized by hydrogen. Indium phosphide oxidation has been found to be an activated process and strongly structure sensitive. The In-rich (2 x 4) surface reacted with oxygen at 300 K and above. X-ray photoemission spectra revealed that the O 2 dissociatively chemisorbed onto the (2 x 4), inserting into the In-In dimer and In-P back bonds. By contrast, the P-rich (2 x 1) reconstruction did not absorb oxygen up to 5 x 105 L at 300 K. Above 455 K, oxygen reacted with the (2 x 1) inserting preferentially into the In-P back bonds and to a lesser extent into the phosphorus dimer bonds.

Chen, Gangyi

381

Treatment of Produced Water Using a Surfactant Modified Zeolite/Vapor Phase Bioreactor System  

SciTech Connect

Co-produced water from the oil and gas industry accounts for a significant waste stream in the United States. Produced waters typically contain a high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component as well as chemicals added during the oil-production process. It has been estimated that a total of 14 billion barrels of produced water were generated in 2002 from onshore operations (Veil, 2004). Although much of this produced water is disposed via reinjection, environmental and cost considerations can make surface discharge of this water a more practical means of disposal. In addition, reinjection is not always a feasible option because of geographic, economic, or regulatory considerations. In these situations, it may be desirable, and often necessary from a regulatory viewpoint, to treat produced water before discharge. It may also be feasible to treat waters that slightly exceed regulatory limits for re-use in arid or drought-prone areas, rather than losing them to reinjection. A previous project conducted under DOE Contract DE-AC26-99BC15221 demonstrated that surfactant modified zeolite (SMZ) represents a potential treatment technology for produced water containing BTEX. Laboratory and field experiments suggest that: (1) sorption of benzene, toluene, ethylbenzene and xylenes (BTEX) to SMZ follows linear isotherms in which sorption increases with increasing solute hydrophobicity; (2) the presence of high salt concentrations substantially increases the capacity of the SMZ for BTEX; (3) competitive sorption among the BTEX compounds is negligible; and, (4) complete recovery of the SMZ sorption capacity for BTEX can be achieved by air sparging the SMZ. This report summarizes research for a follow on project to optimize the regeneration process for multiple sorption/regeneration cycles, and to develop and incorporate a vapor phase bioreactor (VPB) system for treatment of the off-gas generated during air sparging. To this end, we conducted batch and column laboratory SMZ and VPB experiments with synthetic and actual produced waters. Based on the results of the laboratory testing, a pilot scale study was designed and conducted to evaluate the combined SMZ/VPB process. An economic and regulatory feasibility analysis was also completed as part of the current study to assess the viability of the process for various water re-use options.

Lynn E. Katz; Kerry A. Kinney; Robert S. Bowman; Enid J. Sullivan; Soondong Kwon; Elaine B. Darby; Li-Jung Chen; Craig R. Altare

2006-01-31

382

Toxicological evaluation of cigarettes with two banded cigarette paper technologies.  

PubMed

A tiered testing strategy has been employed to evaluate the potential of tobacco processes, ingredients, or technological developments to change the biological activity resulting from burning cigarette tobacco. The strategy is based on comparative chemical and biological testing. The introduction of banded cigarette papers in cigarettes to meet New York state "Fire Safety Standards for Cigarettes" constitutes an example of a technological development evaluated utilizing this tiered testing strategy that included a comparison of the chemical and biological effects of cigarettes with and without the banded cigarette paper technologies (BCPT) (representative of current marketed technologies). Specific testing included mainstream cigarette smoke chemistry studies; in vitro studies included genotoxicity (Ames and sister chromatid exchange) and cytotoxicity studies (neutral red); in vivo studies included a 13-week inhalation study in Sprague-Dawley rats and a 30-week dermal tumor promotion study in SENCAR mice. Collectively, data indicated that cigarettes with and without BCPT had a similar toxicological profile in this test battery. PMID:17590321

Theophilus, Eugenia H; Pence, Deborah H; Meckley, Daniel R; Keith Shreve, W; Ayres, Paul H; Bombick, Betsy R; Borgerding, Michael F; Garner, Charles D; Swauger, James E

2007-09-01

383

The partition coefficients of ethylene between vapor and hydrate phase for methane + ethylene + THF + water systems  

Microsoft Academic Search

The vapor-hydrate equilibria were studied experimentally in detail for CH4+C2H4+tetrahydrofuran (THF)+water systems in the temperature range of 273.15–282.15K, pressure range of 2.0–4.5MPa, the initial gas–liquid volume ratio range of 45–170 standard volumes of gas per volume of liquid and THF concentration range of 4–12mol%. The results demonstrated that, because of the presence of THF, ethylene was remarkably enriched in vapor

L.-W. Zhang; G.-J. Chen; C.-Y. Sun; Y.-M. Ding; L.-Y. Yang

2006-01-01

384

Early specific free radical-related cytotoxicity of gas phase cigarette smoke and its paradoxical temporary inhibition by tar: An electron paramagnetic resonance study with the spin trap DEPMPO.  

PubMed

Electron paramagnetic resonance (EPR) spin trapping studies demonstrated aqueous tar particulate matter (TPM) and gas phase cigarette smoke (GPCS) to behave as different sources of free radicals in cigarette smoke (CS) but their cytotoxic implications have been only assessed in CS due to its relevance to the natural smoking process. Using a sensitive spin trapping detection with 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO), this study compared the respective roles of CS- and GPCS-derived free radicals on smoke-induced cytotoxicity and lipid peroxidation of filtered and unfiltered, machine-smoked experimental and reference cigarettes yielding a wide range of TPM yields. In buffer bubbled with CS the DEPMPO/superoxide spin adduct was the major detected nitroxide. Use of appropriate control experiments with nitric oxide radical (NO*) or carbonyl sulfide, and a computer analysis of spin adduct diastereoisomery showed that the hydroxyl radical (HO*) adduct of DEPMPO seen in GPCS-bubbled was rather related to metal-catalyzed nucleophilic synthesis than to direct HO* trapping. Unexpectedly a protective effect of TPM on murine 3T3 fibroblasts was observed in early (<3h) free radical-, GPCS-induced cell death, and carbon filtering decreased free radical formation, toxicity and lipid peroxidation in three cell lines (including human epithelial lung cells) challenged with GPCS. These results highlight an acute, free radical-dependent, harmful mechanism specific to the GPCS phase, possibly involving NO* chemistry, whose physical or chemical control may be of great interest with the aim of reducing the toxicity of smoke. PMID:17083924

Culcasi, Marcel; Muller, Agnès; Mercier, Anne; Clément, Jean-Louis; Payet, Olivier; Rockenbauer, Antal; Marchand, Véronique; Pietri, Sylvia

2006-12-15

385

Flavoured cigarettes, sensation seeking and adolescents’ perceptions of cigarette brands  

Microsoft Academic Search

Objectives:This study examined the interactive effects of cigarette package flavour descriptors and sensation seeking on adolescents’ brand perceptions.Methods:High school students (n = 253) were randomly assigned to one of two experimental conditions and sequentially exposed to cigarette package illustrations for three different brands. In the flavour descriptor condition, the packages included a description of the cigarettes as “cherry”, while in

K C Manning; K J Kelly; M L Comello

2009-01-01

386

Experimental Determination of the Vapor Phase Thermal Conductivity of Blowing Agents for Polyurethane Rigid Foam  

Microsoft Academic Search

Blowing agents are mainly responsible for the insulation properties of polyurethane rigid foams. Detailed knowledge about the vapor conductivity of blowing agents and their mixtures is essential for their basic understanding. In addition to their insulation properties, blowing agents to a large extent determine the mechanical properties of the foam. Today, blowing agent mixtures are often used in an attempt

T. Heinemann; W. Klaen; R. Yourd; R. Dohrn

2000-01-01

387

Evaluation of Catalysts from Different Origin for Vapor Phase Upgrading in Biomass Pyrolysis  

SciTech Connect

Liquid fuels and chemicals from biomass resources arouse much interests in research and development. Fast pyrolysis of biomass has the potential to effectively change solid biomass materials into liquid products. However, bio-oil from traditional pyrolysis processes is difficult to apply in industry, because of its complicated composition, high oxygen content, low stability, etc. Upgrading or refining of the bio-oil should be performed for industrial application of biomass pyrolysis. Often, the process would be done in a separate reactor downstream of the pyrolysis process. In this paper, a laboratory scale micro test facility was constructed, wherein the pyrolysis of pine and catalytic upgrading of the resulting vapors were closely coupled in one reactor. The composition of vapor effluent was monitored with a molecular beam mass spectrometer (MBMS) for the online evaluation of the catalyst performance. Catalysts from different origin were tested and compared for the effectiveness of pyrolysis vapor upgrading, namely commercial zeolites, Ni based steam reforming catalyst, CaO, MgO, and several laboratory-made catalysts. The reaction temperature for catalytic upgrading varied between 400 and 600 centigrade, and the gaseous residence time ranged from 0.1 second to above 2 second, to simulate the conditions in industrial application. It is revealed that some catalysts are active in transform most of primary biomass pyrolysis vapors into hydrocarbons, resulting in nonoxygenated products, which is beneficial for downstream utilization. Others are not as effective, results in minor improvement compared with blank test results.

Zhang, X.; Mukarakate, C.; Zheng, Z.; Nimlos, M.

2012-01-01

388

Infrared spectroscopic studies of the conformation in ethyl alpha-haloacetates in the vapor, liquid and solid phases.  

PubMed

Infrared spectra of ethyl alpha-fluoroacetate, ethyl alpha-chloroacetate, ethyl alpha-bromoacetate and ethyl alpha-iodoacetate have been measured in the solid, liquid and vapor phases in the region 4000-200 cm(-1). Vibrational frequency assignment of the observed bands to the appropriate modes of vibration was made. Calculations at DFT B3LYP/6-311+G** level, Job: conformer distribution, using Spartan program '08, release 132 was made to determine which conformers exist in which molecule. The results indicated that the first compound exists as an equilibrium mixture of cis and trans conformers and the other three compounds exist as equilibrium mixtures of cis and gauche conformers. Enthalpy differences between the conformers have been determined experimentally for each compound and for every phase. The values indicated that the trans of the first compound is more stable in the vapor phase, while the cis is the more stable in both the liquid and solid phases. In the other three compounds the gauche is more stable in the vapor and liquid phases, while the cis conformer is the more stable in the solid phase for each of the second and third compound, except for ethyl alpha-iodoacetate, the gauche conformer is the more stable over the three phases. Molar energy of activation Ea and the pseudo-thermodynamic parameters of activation DeltaH(double dagger), DeltaS(double dagger) and DeltaG(double dagger) were determined in the solid phase by applying Arrhenius equation; using bands arising from single conformers. The respective E(a) values of these compounds are 5.1+/-0.4, 6.7+/-0.1, 7.5+/-1.3 and 12.0+/-0.6 kJ mol(-1). Potential energy surface calculations were made at two levels; for ethyl alpha-fluoroacetate and ethyl alpha-chloroacetate; the calculations were established at DFT B3LYP/6-311+G** level and for ethyl alpha-bromoacetate and ethyl alpha-iodoacetate at DFT B3LYP/6-311G* level. The results showed no potential energy minimum exists for the gauche conformer in ethyl alpha-fluoroacetate. PMID:20382068

Jassem, Naserallah A; El-Bermani, Muhsin F

2010-07-01

389

Cigarette smoking may yield nitroarenes.  

PubMed

Cigarette smoke condensates are readily nitrated to mutagenic substances exhibiting the properties expected of nitroarenes. In addition, nitroarenes also appear to be generated during the smoking of cigarettes enriched with nitrates. PMID:7037171

McCoy, E C; Rosenkranz, H S

1982-01-01

390

Se vapor pressure dependence of the phase diagram of the CuGa 1- xIn xSe 2 system  

NASA Astrophysics Data System (ADS)

Phase transition points of the CuGa 1- xIn xSe 2 system are investigated by the differential thermal analysis with varying Se vapor pressure up to 760 Torr. The phase diagrams constructed under controlled Se vapor pressure show that the solidus and liquidus points decrease more than 100°C with increasing Se vapor pressure, and that the temperature zone of the (sphalerite+liquid) phase narrows in the region of same pressure. From the analysis of chemical reactions of CuGa 1- xIn x+2Se mixtures, it is shown that In-rich CuGa 1- xIn xSe 2 bulk crystals can be grown using the selenization horizontal Bridgman method. In this case, it is necessary to optimize the temperature width of the temperature gradient zones in the furnace so as to cover the solidus points at the respective Se vapor pressures.

Matsushita, Hiroaki; Takizawa, Takeo

1998-07-01

391

Smoke chemistry, in vitro and in vivo toxicology evaluations of the electrically heated cigarette smoking system series K.  

PubMed

The Electrically Heated Cigarette Smoking System Series K (EHCSS) produces smoke through the controlled electrical heating of tobacco. Evaluation of the EHCSS was accomplished by comparison with commercial and reference cigarettes, using International Organization for Standardization (ISO) and alternative puffing regimens based on nicotine exposures measured in a short-term clinical study. Using the alternative puffing regimen and compared with conventional cigarettes on a per cigarette basis, the EHCSS had 50-60% reductions in tar and nicotine; at least 90% reductions in carbon monoxide, nitrogen oxides, 1,3-butadiene, isoprene, acrylonitrile, polyaromatic hydrocarbons, hydrogen cyanide, aromatic amines, tobacco specific nitrosamines, and phenol; and least a 40% reduction in 2-nitropropane. Other important smoke constituents in EHCSS smoke were reduced as well. The in vitro studies showed similar large reductions in biological activity. Ames mutagenicity of total particulate matter (TPM) from the EHCSS was reduced by 70-90%; cytotoxicity of the TPM was reduced by approximately 82% and 65% for the gas-vapor phase. In vivo testing under ISO smoking conditions in the mouse skin painting assay demonstrated later dermal tumor onset, lower dermal tumor incidence, reduced dermal tumor multiplicity, and a lower proportion of malignant dermal tumors in EHCSS smoke condensate-exposed mice. Thirty-five day and 90-day nose-only inhalation studies in rats showed reductions in pulmonary inflammation and other biological activity, including histopathological endpoints. We conclude that under the conditions of these in vitro and in vivo studies, the EHCSS demonstrated significantly lower biological activity compared to conventional cigarettes, and may suggest the potential for reductions in human smokers. PMID:18590791

Werley, Michael S; Freelin, Susan A; Wrenn, Susan E; Gerstenberg, Birgit; Roemer, Ewald; Schramke, Heike; Van Miert, Erik; Vanscheeuwijck, Patrick; Weber, Susanne; Coggins, Christopher R E

2008-11-01

392

Dioxins in cigarette smoke  

SciTech Connect

Dioxins in cigarettes, smoke, and ash were determined using gas chromatography/mass spectrometry. The total concentration of polychlorinated dibenzo-p-dioxins (PCDDs) in cigarette smoke was approximately 5.0 micrograms/m3 at the maximum level, whereas various congeners from tetra-octa-chlorodibenzo-p-dioxin (-CDD) were detected. Particullary, the total concentration of hepta-CDD congeners was the highest among these congeners. Mass fragmentograms of various PCDD congeners were similar to those in flue gas samples collected from a municipal waste incinerator. The PCDD congeners that were not present in the cigarettes were found in the smoke samples. The 2,3,7,8-TCDD toxic equivalent value--an index for effects on humans--for total PCDDs in smoke was 1.81 ng/m3 using the toxic factor of the United States Environment Protection Agency. Daily intake of PCDDs by smoking 20 cigarettes was estimated to be approximately 4.3 pg.kg body weight/day. This value was close to that of the ADIs: 1-5 pg.kg body weight/day reported in several countries. A heretofore unrecognized health risk was represented by the presence of PCDDs in cigarette smoke.

Muto, H.; Takizawa, Y.

1989-05-01

393

Cigarette smoking in asthma.  

PubMed

A survey was performed of smoking habits and respiratory symptoms of 106 asthmatic patients attending a hospital out-patient clinic. A quarter of the patients were currently smokers and a further quarter were ex-smokers. Less than a third of the smokers complained of symptoms of wheeze or dyspnoea after smoking. Asthmatic smokers had a much higher prevalence of chronic cough but their lung function appeared no lower than non-smokers. Ten asthmatic smokers were selected to contrast their acute bronchial response to smoking a currently marketed cigarette with that of ten asymptomatic smokers. Only four of ten asthmatic patients and two of ten asymptomatic smokers developed acute airway narrowing after smoking despite changes in venous blood nicotine levels which confirmed cigarette smoke inhalation. Many more asthmatic patients smoke than might be expected from the known instability of their airways. Our failure to show frequent and substantial airway reactivity to cigarette smoke in these patients suggests either that cigarette smoke may not be as acutely irritant as might be anticipated or that some asthmatic patients acquire tolerance to it. The effects of chronic cigarette consumption could be demonstrated even in this small sample which suggests that asthmatic patients should be advised to stop smoking, especially as many clinicians expect asthma and smoking to be a rare coincidence. PMID:7426367

Higenbottam, T W; Feyeraband, C; Clark, T J

1980-07-01

394

A Fundamental Study of Vapor Generation from Nonaqeuous Phase Liquid Sources as a Function of Soil Moisture  

NASA Astrophysics Data System (ADS)

The intrusion of vapor phase contaminants from subsurface sources into occupied buildings represents a possible exposure pathway and threat to human health. To make informed risk-management decisions regarding this pathway, it is important to build a conceptual model of the physical and chemical processes that govern vapor intrusion, and specifically to understand the source of the contaminant vapors. One vapor source includes nonaqueous phase liquids (NAPLs) entrapped within the vadose zone. The generation of vapors in the vadose zone from these sources under transient conditions imparted by the heat and water flux boundary conditions at the land surface involves complex mass-transfer processes; partitioning occurs simultaneously between NAPL, air, water and soil phases. Advection and diffusion within the air and water phases also play a critical role. It is our contention that the mass transfer to the air phase is a strong function of the soil moisture conditions in the direct vicinity of the NAPL source. We hypothesize that NAPL sources located in zones of high water saturation will have lower effective mass transfer rates than NAPLs located in low saturation regions, due to the higher diffusion resistance in the aqueous phase. Several studies have investigated NAPL mass transfer under unsaturated conditions and variable soil moisture (Ho and Udell 1992; Wilkins et al. 1995; Yoon et al. 2002); however, to build on this knowledge base, laboratory experimentation is needed under controlled conditions that considers spatially and temporally variable airflow fields and soil moisture saturations that occur in source zones in response to rain events and other climatic phenomena. The fundamental knowledge needed to address field problems cannot be generated in field systems due to lack of control and geologic complexities that are hard to characterize, leading to the need to use intermediate scale test systems. To investigate this problem, experiments were first conducted in a small 2-D porous media tank (28cm x 13cm x 2.5cm) with differing source and soil moisture distributions. Airflow was generated through the tank and the concentrations of the volatile contaminant quantified, allowing estimation of the mass transfer behavior. A mechanistic model was developed simultaneously, and demonstrated that it could represent the data from the experiment. An upscaled experiment was conducted in a large porous media tank (4.9m x 1.2m x 6 cm), to determine if the model can capture the up-scaled system. This intermediate scale tank was subjected to infiltration events and has a complex airflow field more representative of field conditions. The results from the model and the experiment gave an improved understanding of processes that control vapor generation and a better conceptual model for this exposure pathway. This presentation will discuss the results of the intermediate scale tank experiment and associated modeling effort. Ho, C. K. and K. K. Udell (1992). J. Contam. Hydrol. 11(3-4): 291. Wilkins, M. D., L. M. Abriola, et al. (1995). Water Resour. Res. 31(9): 2159-2172. Yoon, H., J. H. Kim, et al. (2002). J. Contam. Hydrol. 54: 1-18.

Petri, B. G.; Illangasekare, T. H.; Sauck, C.; Sakaki, T.; Christ, J.

2011-12-01

395

Carbonaceous resin capsule for vapor-phase monitoring of volatile hydrocarbons in soil: partitioning and kinetic model verification.  

PubMed

The resin capsule system (RCS) was tested as a means of providing data on the presence and forms of volatile hydrocarbons. Results indicated that resin capsules provided data showing sensitivity to soil variables (texture and moisture content) and time. The objectives of this paper are to evaluate the RCS methodology and to determine whether carbonaceous resin capsules provide results that can be described by fundamental chemical partitioning and kinetic principles. Findings revealed a significant relationship between quantities of benzene, toluene, ethylbenzene, and xylene adsorbed on the capsule and quantities partitioned into the vapor phase. Kinetic evaluation indicated that the vapor adsorption by the resin capsule is regulated by diffusion processes. No verification of rate-limiting processes was possible due to limitations imposed by the experimental design, but it appears that during early stages, adsorption rate was limited by vapor diffusion through the soil. The resin capsule data also reflected differences that would be expected due to properties of the organic liquids present. These results provide further evidence that the RCS could be developed to suggest direct in situ monitoring to reveal quantities and nature of organic substances in soils. PMID:23703586

Yang, Jae E; Skogley, Earl O; Ahmad, Mahtab; Lee, Sang Soo; Ok, Yong Sik

2013-12-01

396

Large misorientation of GaN films grown on r-plane sapphire substrates by metalorganic vapor-phase epitaxy  

Microsoft Academic Search

The lattice orientation of epitaxial GaN films grown on r-plane sapphire substrates by atmospheric metalorganic vapor-phase epitaxy was investigated. It is generally known that nonpolar a-plane GaN layers are grown on r-plane sapphire substrates. However, high-resolution X-ray diffraction revealed the large misorientation of GaN grown on r-plane sapphire when the growth temperature was increased from1100°C to 1150°C. The c-axis was

Kazuhide Kusakabe; Shizutoshi Ando; Kazuhiro Ohkawa

2007-01-01

397

Vapor-phase esterification of acetic acid with ethanol catalyzed by a macroporous sulfonated styrene-divinylbenzene (20%) resin  

SciTech Connect

The kinetics of the vapor-phase (85-120/sup 0/C) esterification of acetic acid with ethyl alcohol, at atmospheric pressure, catalyzed by a macroporous sulfonated styrene-divinylbenzene (DVB;20%) resin, has been studied. A simple first-order model (r = kp/sub 1/) fits experimental kinetic data properly for a constant reactants ratio. Discussion by means of L-H-H-W models shows that the rate-controlling step is the surface reaction with a single-site mechanism. The apparent activation energy is 4000 cal/mol.

Gimenez, J.; Costa, J.; Cervera, S.

1987-02-01

398

Thermodynamics on hydride vapor phase epitaxy of AlN using AlCl3 and NH3  

Microsoft Academic Search

A thermodynamic analysis on hydride vapor phase epitaxy (HVPE) of AlN using AlCl3 and NH3 was performed. Regardless of the carrier gas used, partial pressures of Al-containing gaseous species [AlCl3, AlCl2, AlCl and (AlCl3)2] in equilibrium with AlN are significantly low in the temperature range of 500-1500 °C when the input V\\/III ratio is above 1. This means that the

Y. Kumagai; K. Takemoto; J. Kikuchi; T. Hasegawa; H. Murakami; A. Koukitu

2006-01-01

399

Dislocation reduction of InAs nanofins prepared on Si substrate using metal-organic vapor-phase epitaxy  

PubMed Central

InAs nanofins were prepared on a nanopatterned Si (001) substrate by metal-organic vapor-phase epitaxy. The threading dislocations, stacked on the lowest-energy-facet plane {111}, move along the SiO2 walls, resulting in a dislocation reduction, as confirmed by transmission electron microscopy. The dislocations were trapped within a thin InAs epilayer. The obtained 90-nm-wide InAs nanofins with an almost etching-pit-free surface do not require complex intermediate-layer epitaxial growth processes and large thickness typically required for conventional epitaxial growth.

2012-01-01

400

Thermodynamics of the gas-phase reactions in chemical vapor deposition of silicon carbide with methyltrichlorosilane precursor  

Microsoft Academic Search

The gas-phase reaction thermodynamics in the chemical vapor deposition system of preparing silicon carbide via methyltrichlorosilane\\u000a pyrolysis is investigated with a relatively complete set of 226 species, in which the thermodynamic data of 163 species are\\u000a evaluated in this work with accurate model chemistry G3(MP2) and G3\\/\\/B3LYP calculations combined with standard statistical\\u000a thermodynamics. The data include heat capacity (C\\u000a \\u000a p,m?),

Juanli Deng; Kehe Su; Xin Wang; Qingfeng Zeng; Laifei Cheng; Yongdong Xu; Litong Zhang

2009-01-01

401

Analysis of Dislocations Generated during Metal--Organic Vapor Phase Epitaxy of GaN on Patterned Templates  

NASA Astrophysics Data System (ADS)

We report on patterning and subsequent metal--organic vapor phase epitaxy overgrowth of GaN films on patterned GaN/sapphire templates. Templates with a hexagonal hole pattern were prepared by photolithography and dry etching. After GaN overgrowth voids were formed at the GaN/sapphire interface. Threading dislocations were found to bend and terminate at void sidewalls during the overgrowth resulting in improved material quality. The dislocations were analyzed by transmission electron microscopy combined with energy dispersive X-ray spectroscopy. Areas with increased Ga concentration were found at the tips of coalesced voids that introduced additional dislocations to the overgrown films.

Suihkonen, Sami; Ali, Muhammad; Törmä, Pekka T.; Sintonen, Sakari; Svensk, Olli; Sopanen, Markku; Lipsanen, Harri; Nevedomsky, Vladimir N.; Bert, Nikolay A.

2013-01-01

402

Ammonia: A source of hydrogen dopant for InN layers grown by metal organic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Thermal annealing of InN layers grown by metal organic vapor phase epitaxy (MOVPE) is investigated in nitrogen atmosphere for temperatures ranging from 400 to 550 °C and for heat treatment times up to 12 h. This treatment results in hydrogen outdiffusion, lowering significantly the residual n-type background doping. This mechanism is shown to be reversible through thermal annealing under ammonia atmosphere, responsible of hydrogen incorporation during growth. These results establish a MOVPE process allowing the obtention of InN samples, which exhibit similar electrical properties than molecular beam epitaxy grown samples: a key issue in view of future industrial production of InN based devices.

Ruffenach, S.; Moret, M.; Briot, O.; Gil, B.

2009-07-01

403

Identification of vapor-phase chemical warfare agent simulants and rocket fuels using laser-induced breakdown spectroscopy  

SciTech Connect

Application of laser-induced breakdown spectroscopy (LIBS) to the identification of security threats is a growing area of research. This work presents LIBS spectra of vapor-phase chemical warfare agent simulants and typical rocket fuels. A large dataset of spectra was acquired using a variety of gas mixtures and background pressures and processed using partial least squares analysis. The five compounds studied were identified with a 99% success rate by the best method. The temporal behavior of the emission lines as a function of chamber pressure and gas mixture was also investigated, revealing some interesting trends that merit further study.

Stearns, Jaime A.; McElman, Sarah E.; Dodd, James A.

2010-05-01

404

Dislocation reduction of InAs nanofins prepared on Si substrate using metal-organic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

InAs nanofins were prepared on a nanopatterned Si (001) substrate by metal-organic vapor-phase epitaxy. The threading dislocations, stacked on the lowest-energy-facet plane {111}, move along the SiO2 walls, resulting in a dislocation reduction, as confirmed by transmission electron microscopy. The dislocations were trapped within a thin InAs epilayer. The obtained 90-nm-wide InAs nanofins with an almost etching-pit-free surface do not require complex intermediate-layer epitaxial growth processes and large thickness typically required for conventional epitaxial growth.

Hsu, Chao-Wei; Chen, Yung-Feng; Su, Yan-Kuin

2012-11-01

405

Aromatization of n-hexane by platinum-containing molecular sieves. 1. Catalyst preparation by the vapor phase impregnation method  

Microsoft Academic Search

A vapor phase impregnation method with Pt(acac)â has been developed and used to load Pt into aluminosilicate (KL, BaKL, NaY, CsNaY, cubic and hexagonal polytypes of faujasite, ZSM-12, and SSZ-24) and aluminophosphate (AlPOâ-5 and VPI-5) molecular sieves. Pt-containing molecular sieves are characterized by XRD,TPD, elemental analysis, ¹³C MAS NMR, TEM, and Hâ chemisorption. ¹³C MAS NMR, TEM, and Hâ chemisorption

Suk Bong Hong; E. Mielczarski; M. E. Davis

1992-01-01

406

A flux induced crystal phase transition in the vapor-liquid-solid growth of indium-tin oxide nanowires.  

PubMed

Single crystalline metal oxide nanowires formed via a vapor-liquid-solid (VLS) route provide a platform not only for studying fundamental nanoscale properties but also for exploring novel device applications. Although the crystal phase variation of metal oxides, which exhibits a variety of physical properties, is an interesting feature compared with conventional semiconductors, it has been difficult to control the crystal phase of metal oxides during the VLS nanowire growth. Here we show that a material flux critically determines the crystal phase of indium-tin oxide nanowires grown via the VLS route, although thermodynamical parameters, such as temperature and pressure, were previously believed to determine the crystal phase. The crystal phases of indium-tin oxide nanowires varied from the rutile structures (SnO2), the metastable fluorite structures (InxSnyO3.5) and the bixbyite structures (Sn-doped In2O3) when only the material flux was varied within an order of magnitude. This trend can be interpreted in terms of the material flux dependence of crystal phases (rutile SnO2 and bixbyite In2O3) on the critical nucleation at the liquid-solid (LS) interface. Thus, precisely controlling the material flux, which has been underestimated for VLS nanowire growths, allows us to design the crystal phase and properties in the VLS nanowire growth of multicomponent metal oxides. PMID:24842296

Meng, Gang; Yanagida, Takeshi; Yoshida, Hideto; Nagashima, Kazuki; Kanai, Masaki; Zhuge, Fuwei; He, Yong; Klamchuen, Annop; Rahong, Sakon; Fang, Xiaodong; Takeda, Seiji; Kawai, Tomoji

2014-05-29

407

The Layou Tuff, Dominica: an Example of an Ignimbrite Showing Extensive Vapor-Phase Crystallization  

NASA Astrophysics Data System (ADS)

The island of Dominica, located in the central part of the Lesser Antilles island arc, has witnessed, probably in the last 100,000 years, three large-volume Plinian eruptions. One of these from the Morne Trois Pitons center generated extensive ignimbrites (>62 km2) that extend as two tongues NE and NW from the Morne Trois Pitons caldera (now infilled by a dome complex). Preliminary studies on the NW fan, which filled the valley of the paleo-Layou River and reached the west coast near its mouth, shows that this ignimbrite sequence may be subdivided into an unlithified and a lithified facies. The former occurs in distal exposures along the edge of the ignimbrite, whereas the latter is dominant in the central valley-fill locations. The Layou ignimbrite in its most distal exposure overlies a thick sequence of fluviatile conglomerates. At this location the initial deposit is a pumiceous lapilli fall unit, 18 cm thick. Lithic clast sizes in this unit appear to be consistent with an eruption column height of 20-25 km. This deposit is followed by a thin ash-rich fall layer rich in accretionary lapilli (up to 8 mm in diameter), suggesting magma-water interaction. Overlying these fall deposits are at least 3 ignimbrite flow units. These unlithified units have a maximum thickness of over 20 m. Within the Layou valley the ignimbrites become thicker (reaching a maximum of 180 m in the upper Layou valley) and are lithified through out their exposed thickness. A 17 m section through these lithified deposits a few kilometers inland from the unlithified deposits described above suggest, based on density variations, that the maximum zone of lithification occurs 5 m above the lowest exposure of the section (i.e. approximately 15 m above the unlithified base of the deposit). Pumices in these lithified deposits do not appear to show any flattening or preferred orientation; rather the changes in density appear to be related to a decrease in the porosity of the matrix as a consequence of vapor-phase crystallization. Grain size studies on the unlithified facies suggest the Layou ignimbrite has lost more than 40% of its vitric material from the finer size fractions (< 1 mm). Whole rock array calculations suggest this vitric loss was caused by high gas flow through the deposit. These gases, which were probably dominantly heated groundwater would, according to recent experiments on the effect of water on welding, have coated the shards with sublimates. This would have inhibited sintering so that adhesion between clasts would have been principally by precipitation of sublimates in pore spaces, thus producing a sillar rather than a welded tuff. Thick lithified sequences are also associated with the other two ignimbrite sequences on Dominica and a comparison will be made between the Layou ignimbrite and these sequences as well as other non-lithified ignimbrites to better define the conditions of ignimbrite deposition and lithification in a wet tropical environment.

Tinnin, B.; Smith, A. L.; Fryxell, J. E.; Daly, G.

2006-12-01

408

Vapor-liquid phase equilibria of water modelled by a Kim-Gordon potential  

SciTech Connect

Gibbs ensemble Monte Carlo simulations were carried out to investigate the properties of a frozen-electron-density (or Kim-Gordon, KG) model of water along the vapor-liquid coexistence curve. Because of its theoretical basis, such a KG model provides for seamless coupling to Kohn-Sham density functional theory for use in mixed quantum mechanics/molecular mechanics (QM/MM) implementations. The Gibbs ensemble simulations indicate rather limited transferability of such a simple KG model to other state points. Specifically, a KG model that was parameterized by Barker and Sprik to the properties of liquid water at 300 K, yields saturated vapor pressures and a critical temperature that are significantly under- and over-estimated, respectively.

Maerzke, K A; McGrath, M J; Kuo, I W; Tabacchi, G; Siepmann, J I; Mundy, C J

2009-03-16

409

RECENT ADVANCES IN RAPID VAPOR-PHASE DENSIFICATION OF THICK REFRACTORY CARBON-CARBON COMPOSITES  

Microsoft Academic Search

Refractory carbon fiber-matrix composites are attractive for use in aircraft brake pads and in uncooled engine and rocket sections due to their low density and superb mechanical and thermal properties. Most articles are produced by densification of porous, final-shape fiber preforms, by means of multiple cycles of isothermal isobaric chemical vapor infiltration (IICVI) and\\/or liquid resin impregnation with high-temperature treatment.

Ilan Golecki

410

Thin film solid-state lithium batteries prepared by consecutive vapor-phase processes  

Microsoft Academic Search

Thin-film solid-state lithium batteries of total thickness less than 20 microns were prepared. These thin lithium batteries were fabricated using a thin film of TiS2 prepared by chemical vapor deposition (CVD) as the cathode active material, a thin film of solid polymer prepared by plasma polymerization as the electrolyte, and a thin film of lithium deposited by thermal evaporation as

Zen-Ichiro Takehara; Zempachi Ogumi; Yoshiharu Uchimoto; Eishi Endo; Yoshinori Kanamori

1991-01-01

411

Rolling Contact Testing of Vapor Phase Lubricants—Part II: System Performance Evaluation  

Microsoft Academic Search

The relative effects of several vapor lubrication parameters on bearing performance were examined using a ball-on-rod tester. Lubricants included in the evaluation were a tertiary-butylphenyl phosphate (TBPP), a 2 cSt polyalphaolefin blended with 15 percent TBPP (PAO+), the TBPP blended with 33 percent tributyl phosphate (TBPP+), a cyclophosphazine (X-1P), a polyphenylether (5P4E), and a perfluoroalkylether (Z). Parameters included in the

Nelson H. Forster; Hitesh K. Trivedi

1997-01-01

412

Characterization of single-crystal diamond grown from the vapor phase on substrates of natural diamond  

SciTech Connect

The results of studies of single-crystal diamond layers with orientation (100) grown on substrates of IIa-type natural diamond by chemical-vapor deposition and of semiconductor diamond obtained subsequently by doping by implantation of boron ions are reported. Optimal conditions of postimplantation annealing of diamond that provide the hole mobility of 1150 cm{sup 2} V{sup -1} s{sup -1} (the highest mobility obtained so far for semiconductor diamond after ion implantation) are given.

Altukhov, A. A. [ITC UralAlmazInvest (Russian Federation); Vikharev, A. L.; Gorbachev, A. M. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation); Dukhnovsky, M. P.; Zemlyakov, V. E. [FSUE Istok (Russian Federation); Ziablyuk, K. N.; Mitenkin, A. V. [ITC UralAlmazInvest (Russian Federation); Muchnikov, A. B., E-mail: mabl@appl.sci-nnov.ru; Radishev, D. B. [Russian Academy of Sciences, Institute of Applied Physics (Russian Federation); Ratnikova, A. K.; Fedorov, Yu. Yu. [FSUE Istok (Russian Federation)

2011-03-15

413

Vapor-phase transport in the near-drift environment at Yucca Mountain  

NASA Astrophysics Data System (ADS)

A key issue regarding the performance of the potential high-level radioactive waste repository at Yucca Mountain, Nevada, is the likelihood of precipitation percolating a vertical distance of ˜300 m through fractured unsaturated rock into drifts containing waste packages. Water enhances waste package corrosion and is required for transport of released radionuclides. To evaluate the propensity for seepage into tunnels at Yucca Mountain, a 5-m-diameter, 2.7-km-long tunnel, commonly referred to as the Cross Drift (CD), was excavated in 1998, branching off from the main Exploratory Studies Facility tunnel. Sections of this tunnel have been isolated from ventilation for extended periods over the last 4 years. We present continuous measurements of relative humidity and temperature and periodic observations of liquid water in the CD over two periods. During this observation duration the terminal section of the drift was partitioned into four sections by bulkheads, and ventilation to these sections was minimized to a few days. We compare these observations to results from analytical and numerical models to investigate processes associated with the movement of water vapor between the tunnel bore and the surrounding fractured rock formation. Observations from this effort indicate that fractures can be primary paths for unsaturated zone vapor flow in the immediate vicinity of emplacement drifts. Observations, measurements, and analysis indicate the need for a model that includes fracture-dominated vapor transport as a significant contributor to total water flow into the drifts.

Salve, Rohit; Kneafsey, Timothy J.

2005-01-01

414

Vapor-phase transport in the near-drift environment at Yucca Mountain  

NASA Astrophysics Data System (ADS)

A key issue regarding the performance of the potential high-level radioactive waste repository at Yucca Mountain, Nevada, is the likelihood of precipitation percolating a vertical distance of ~300 m through fractured unsaturated rock into drifts containing waste packages. Water enhances waste package corrosion and is required for transport of released radionuclides. To evaluate the propensity for seepage into tunnels at Yucca Mountain, a 5-m-diameter, 2.7-km-long tunnel, commonly referred to as the Cross Drift (CD), was excavated in 1998, branching off from the main Exploratory Studies Facility tunnel. Sections of this tunnel have been isolated from ventilation for extended periods over the last 4 years. We present continuous measurements of relative humidity and temperature and periodic observations of liquid water in the CD over two periods. During this observation duration the terminal section of the drift was partitioned into four sections by bulkheads, and ventilation to these sections was minimized to a few days. We compare these observations to results from analytical and numerical models to investigate processes associated with the movement of water vapor between the tunnel bore and the surrounding fractured rock formation. Observations from this effort indicate that fractures can be primary paths for unsaturated zone vapor flow in the immediate vicinity of emplacement drifts. Observations, measurements, and analysis indicate the need for a model that includes fracture-dominated vapor transport as a significant contributor to total water flow into the drifts.

Salve, Rohit; Kneafsey, Timothy J.

2005-01-01

415

Toward a Monte Carlo program for simulating vapor-liquid phase equilibria from first principles  

SciTech Connect

Efficient Monte Carlo algorithms are combined with the Quickstep energy routines of CP2K to develop a program that allows for Monte Carlo simulations in the canonical, isobaric-isothermal, and Gibbs ensembles using a first principles description of the physical system. Configurational-bias Monte Carlo techniques and pre-biasing using an inexpensive approximate potential are employed to increase the sampling efficiency and to reduce the frequency of expensive ab initio energy evaluations. The new Monte Carlo program has been validated through extensive comparison with molecular dynamics simulations using the programs CPMD and CP2K. Preliminary results for the vapor-liquid coexistence properties (T = 473 K) of water using the Becke-Lee-Yang-Parr exchange and correlation energy functionals, a triple-zeta valence basis set augmented with two sets of d-type or p-type polarization functions, and Goedecker-Teter-Hutter pseudopotentials are presented. The preliminary results indicate that this description of water leads to an underestimation of the saturated liquid density and heat of vaporization and, correspondingly, an overestimation of the saturated vapor pressure.

McGrath, M; Siepmann, J I; Kuo, I W; Mundy, C J; Vandevondele, J; Sprik, M; Hutter, J; Mohamed, F; Krack, M; Parrinello, M

2004-10-20

416

Biological vapor-phase treatment using biofilter and biotrickling filter reactors: Practical operating regimes  

SciTech Connect

The biological treatment of volatile organic compounds (VOCs) and air toxics has received increased attention in recent years. Biotreatment of airborne contaminants offers an inexpensive alternative to conventional air treatment technologies such as carbon adsorption and incineration. Most biological air treatment technologies commercially available are fixed-film systems that rely on growth of a biofilm layer on an inert organic support such as compost or peat (biofilters), or an inorganic support such as ceramic or plastic (biotrickling filters). If designed properly, these systems combine the advantages of high biomass concentration with high specific surface area for mass transfer. At economically viable vapor residence times (1 to 1.5 minutes), biofilters can be used for treating vapor streams containing up to approximately 1500 [mu]g/L of readily biodegradable compounds. Biotrickling filters may offer greater performance than biofilters at high contaminant loadings, possibly due to higher internal biomass concentrations. Both systems are best suited for treating vapor streams containing one or two major compounds. If designed properly, biofilters are especially well suited for treating streams that vary in concentration from minute to minute. 11 refs., 8 figs.

Togna, A.P.; Singh, M. (Envirogen, Inc., Lawrenceville, NJ (United States))

1994-05-01

417

Stability of evaporating water when heated through the vapor and the liquid phases.  

PubMed

The stability of a water layer of uniform thickness held in a two-dimensional container of finite or semi-infinite extent is examined using linear stability theory. The liquid-vapor interface can be heated both through the liquid and through the vapor, as previously experimentally reported. The need to introduce a heat transfer coefficient is eliminated by introducing statistical rate theory (SRT) to predict the evaporation flux. There are no fitting or undefined parameters in the expression for the evaporation flux. The energy transport is parametrized in terms of the evaporation number, Eev, that for a given experimental circumstance can be predicted. The critical Marangoni number for the finite, Macf, and for the semi-infinite system, Mac(infinity), can be quantitatively predicted. Experiments in which water evaporated from a stainless-steel funnel and from a polymethyl methacrylate (PMMA) funnel into its vapor have been previously reported. Marangoni convection was observed in the experiments that used the stainless-steel funnel but not with the PMMA funnel even though the Marangoni number for the PMMA funnel was more than 27,000. The SRT-based stability theory indicates that the critical value of the Marangoni number for the experiments with the PMMA funnel was greater than the experimental value of the Marangoni number in each case; thus, no Marangoni convection was predicted to result from an instability. The observed convection with the stainless-steel funnel resulted from a temperature gradient imposed along the interface. PMID:20365865

Das, Kausik S; MacDonald, Brendan D; Ward, C A

2010-03-01

418

Determination of eugenol, anethole, and coumarin in the mainstream cigarette smoke of Indonesian clove cigarettes.  

PubMed

Indonesian clove cigarettes (kreteks), typically have the appearance of a conventional domestic cigarette. The unique aspects of kreteks are that in addition to tobacco they contain dried clove buds (15-40%, by wt.), and are flavored with a proprietary "sauce". Whereas the clove buds contribute to generating high levels of eugenol in the smoke, the "sauce" may also contribute other potentially harmful constituents in addition to those associated with tobacco use. We measured levels of eugenol, trans-anethole (anethole), and coumarin in smoke from 33 brands of clove-flavored cigarettes (filtered and unfiltered) from five kretek manufacturers. In order to provide information for evaluating the delivery of these compounds under standard smoking conditions, a quantification method was developed for their measurement in mainstream cigarette smoke. The method allowed collection of mainstream cigarette smoke particulate matter on a Cambridge filter pad, extraction with methanol, sampling by automated headspace solid-phase microextraction, and subsequent analysis using gas chromatography/mass spectrometry. The presence of these compounds was confirmed in the smoke of kreteks using mass spectral library matching, high-resolution mass spectrometry (+/-0.0002 amu), and agreement with a relative retention time index, and native standards. We found that when kreteks were smoked according to standardized machine smoke parameters as specified by the International Standards Organization, all 33 clove brands contained levels of eugenol ranging from 2,490 to 37,900 microg/cigarette (microg/cig). Anethole was detected in smoke from 13 brands at levels of 22.8-1,030 microg/cig, and coumarin was detected in 19 brands at levels ranging from 9.2 to 215 microg/cig. These detected levels are significantly higher than the levels found in commercial cigarette brands available in the United States. PMID:17583404

Polzin, Gregory M; Stanfill, Stephen B; Brown, Candace R; Ashley, David L; Watson, Clifford H

2007-10-01

419

Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method.  

PubMed

Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-?m thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate. PMID:21711601

Liu, Jianming; Liu, Xianlin; Li, Chengming; Wei, Hongyuan; Guo, Yan; Jiao, Chunmei; Li, Zhiwei; Xu, Xiaoqing; Song, Huaping; Yang, Shaoyan; Zhu, Qinsen; Wang, Zhanguo; Yang, Anli; Yang, Tieying; Wang, Huanhua

2011-01-01

420

Source proximity reflected in spatial and temporal variability in particle and vapor phase Hg concentrations in Detroit, MI  

NASA Astrophysics Data System (ADS)

Vapor-phase Hg, particulate Hg, and total suspended particulate matter were collected from 1 April 1996-31 October 1996 at two sites located in industrial areas of northeast and southwest Detroit, at a suburban residential site 2 km west of Detroit, and at a rural site 60 km west of Detroit as part of a larger study designed to assess the Hg cycling within the urban area. Near-source short-range transport can cause large differences in pollutant concentration and deposition within a small geographic area. Hg deposition and the resulting impact on the local environment is a result not only of the ambient concentrations present, but of the chemical form and physical properties of the pollutant. All site-to-site differences in vapor phase Hg concentration were statistically significant ( p<0.05) with mean concentrations ranging from 1.6-2.8 ng m -3. The mean particulate Hg concentrations ranged from 12.0-54.0 pg m -3 with concentrations at the less industrialized sites significantly lower than those at the industrialized sites ( p<0.05). Hg associated with coarse particles (diameter?2.5 ?m) had a median daily contribution of 37% to the total (range 4-68%) in south-west Detroit vs. a median daily contribution of 20% at the rural sampling site (range 6-37%).

Gildemeister, Amy E.; Graney, Joseph; Keeler, Gerald J.

421

Growth kinetics and mass transport mechanisms of GaN columns by selective area metal organic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Three-dimensional GaN columns recently have attracted a lot of attention as the potential basis for core-shell light emitting diodes for future solid state lighting. In this study, the fundamental insights into growth kinetics and mass transport mechanisms of N-polar GaN columns during selective area metal organic vapor phase epitaxy on patterned SiOx/sapphire templates are systematically investigated using various pitch of apertures, growth time, and silane flow. Species impingement fluxes on the top surface of columns Jtop and on their sidewall Jsw, as well as, the diffusion flux from the substrate Jsub contribute to the growth of the GaN columns. The vertical and lateral growth rates devoted by Jtop, Jsw and Jsub are estimated quantitatively. The diffusion length of species on the SiOx mask surface ?sub as well as on the sidewall surfaces of the 3D columns ?sw are determined. The influences of silane on the growth kinetics are discussed. A growth model is developed for this selective area metal organic vapor phase epitaxy processing.

Wang, Xue; Hartmann, Jana; Mandl, Martin; Sadat Mohajerani, Matin; Wehmann, Hergo-H.; Strassburg, Martin; Waag, Andreas

2014-04-01

422

Investigation of cracks in GaN films grown by combined hydride and metal organic vapor-phase epitaxial method  

PubMed Central

Cracks appeared in GaN epitaxial layers which were grown by a novel method combining metal organic vapor-phase epitaxy (MOCVD) and hydride vapor-phase epitaxy (HVPE) in one chamber. The origin of cracks in a 22-?m thick GaN film was fully investigated by high-resolution X-ray diffraction (XRD), micro-Raman spectra, and scanning electron microscopy (SEM). Many cracks under the surface were first observed by SEM after etching for 10 min. By investigating the cross section of the sample with high-resolution micro-Raman spectra, the distribution of the stress along the depth was determined. From the interface of the film/substrate to the top surface of the film, several turnings were found. A large compressive stress existed at the interface. The stress went down as the detecting area was moved up from the interface to the overlayer, and it was maintained at a large value for a long depth area. Then it went down again, and it finally increased near the top surface. The cross-section of the film was observed after cleaving and etching for 2 min. It was found that the crystal quality of the healed part was nearly the same as the uncracked region. This indicated that cracking occurred in the growth, when the tensile stress accumulated and reached the critical value. Moreover, the cracks would heal because of high lateral growth rate.

2011-01-01

423

Vapor-phase and particulate-associated pesticides and PCB concentrations in eastern North Dakota air samples  

SciTech Connect

Vapor-phase and suspended particulate (<50 {mu}m) samples were collected on polyurethane foam (PUF) and quartz fiber filters in rural North Dakota to determine the air concentrations of pesticides in an area where agriculture is a primary source of semivolatile pollutants. Samples were collected at two sites from 1992 to 1994 that were at least 0.4 km from the nearest farmed fields and known application of pesticides, and analyzed for 22 different organochlorine, triazine, and acid herbicide pesticides. Fourteen pesticides were found above the detection limits (typically <1 pg/m{sup 3}). Concentrations of polychlorinated biphenyl (PCB) congeners were much lower (<50 pg/m{sup 3} in all cases) than many of the pesticides. These results demonstrate that pesticides are among the most prevalent chlorinated semivolatile pollutants present in rural North Dakota, that significant transport of pesticides occurs both in the vapor-phase and on suspended particulate matter, and that blown soil may be a significant mechanism for introducing pesticides into surface and ground waters. 32 refs., 2 figs., 4 tabs.

Hawthorne, S.B.; Miller, D.J.; Louie, P.K.K. [Univ. of North Dakota, Grand Forks, ND (United States)] [and others

1996-05-01

424

CCMR: Conductivity Optimization of Poly(3,4-ethylenedioxythiophene): Tosylate Films Fabricated via Vapor Phase Polymerization for Use in Organic Light-Emitting Diodes (OLEDs)  

NSDL National Science Digital Library

A new conductive polymer, Poly(3,4-ethylenedioxythiophene) (PEDOT) was studied for application in organic light-emitting diodes (OLEDs). Thin film coating of PEDOT was applied through vapor-phase polymerization of 3,4-ethylenedioxythiophene (EDOT) on glass slide substrates coated with Fe (III): Tosylate. Polymerization temperature was optimized to be 30ºC, and the absence of ambient water vapor during polymerization was found to have negative effects on the conductivity. While the conductivity of PEDOT: Tosylate films were not optimized, insight was gained on how water vapor and rate of polymerization affect the overall conductivity of these films.

Newsky, Sarah E.

2009-08-15

425

[Electronic cigarette: Reliable and efficient?].  

PubMed

Before 2010, the e-cigarette remains inefficient then, its dissemination explodes in 2013 where more than 10 million people have tried it in France. The best made e-cigarette will always be potentially toxic and an addictive product. The e-cigarette is not a suitable product for non-smokers and could participate to normalize tobacco in society. To end tobacco, e-cigarette must provide a pleasantthroat hitto the smoker in the first 6seconds then deliver an adequate dose of nicotine. The majority of smokers who have tried the e-cigarette do not adopt the product because they did not like it. Health professional must help those who smoke and use e-cigarettes to remove the last cigarettes. PMID:24890639

Dautzenberg, Bertrand; Dautzenberg, Marie-Dominique

2014-01-01

426

Vapor-phase hydrothermal transformation of HTiOF3 intermediates into {001} faceted anatase single-crystalline nanosheets.  

PubMed

For the first time, a facile, one-pot hydrofluoric acid vapor-phase hydrothermal (HF-VPH) method is demonstrated to directly grow single-crystalline anatase TiO(2) nanosheets with 98.2% of exposed {001} faceted surfaces on the Ti substrate via a distinctive two-stage formation mechanism. The first stage produces a new intermediate crystal (orthorhombic HTiOF(3) ) that is transformed into anatase TiO(2) nanosheets during the second stage. The findings reveal that the HF-VPH reaction environment is unique and differs remarkably from that of liquid-phase hydrothermal processes. The uniqueness of the HF-VPH conditions can be readily used to effectively control the nanostructure growth. PMID:22903795

Liu, Porun; Wang, Yun; Zhang, Haimin; An, Taicheng; Yang, Huagui; Tang, Zhiyong; Cai, Weiping; Zhao, Huijun

2012-12-01

427

Significance of vapor phase chemical reactions on CVD rates predicted by chemically frozen and local thermochemical equilibrium boundary layer theories  

NASA Technical Reports Server (NTRS)

This paper investigates the role played by vapor-phase chemical reactions on CVD rates by comparing the results of two extreme theories developed to predict CVD mass transport rates in the absence of interfacial kinetic barrier: one based on chemically frozen boundary layer and the other based on local thermochemical equilibrium. Both theories consider laminar convective-diffusion boundary layers at high Reynolds numbers and include thermal (Soret) diffusion and variable property effects. As an example, Na2SO4 deposition was studied. It was found that gas phase reactions have no important role on Na2SO4 deposition rates and on the predictions of the theories. The implications of the predictions of the two theories to other CVD systems are discussed.

Gokoglu, Suleyman A.

1988-01-01

428

Motions of Molecules in Condensed Systems. VI. The InfraRed Spectra for Vapor, Liquid and Two Solid Phases of Methyl Chloroform  

Microsoft Academic Search

Infra-red spectra are compared for equivalent absorbing paths of methyl chloroform (1,1,1-trichloroethane) as vapor at 25°, liquid at ?28°, solid I at ?40° and solid II at ?55°C. The spectra differ in the respects: (1) P-Q-R branches observed on some bands in the vapor disappear in the condensed phases, (2) bands generally are sharpened and ones attributable to combinations are

Robert Karplus; Ralph S. Halford

1950-01-01

429

Development of gallium nitride-based ultraviolet and visible light-emitting diodes using hydride vapor-phase epitaxy and molecular beam epitaxy  

Microsoft Academic Search

Much of the work done on ultraviolet (UV) and visible III-Nitrides-based light emitting diodes (LEDs) involves growth by metal-organic chemical vapor deposition (MOCVD). In this dissertation, the growth, development, and fabrication of III-Nitrides-based UV and visible LEDs with very high photon conversion and extraction efficiencies using hydride vapor-phase epitaxy (HVPE) and radio frequency (rf) plasma-assisted molecular beam epitaxy (PAMBE) is

Jasper Sicat Cabalu

2006-01-01

430

Use of Menthol Cigarettes.  

National Technical Information Service (NTIS)

Among past month smokers, the rate of smoking menthol cigarettes increased from 31.0 percent in 2004 to 33.9 percent in 2008; increases were most pronounced for adolescents aged 12 to 17 (43.5 percent in 2004 vs. 47.7 percent in 2008), young adults aged 1...

2009-01-01

431

What's in a Cigarette?  

MedlinePLUS

... paint A A A Share Print State of Tobacco Control 2014 Bring the Fight for Air to your smartphone. Top Stories More about Smoking Cessation My First Cigarette, and My Last May 30, 2014 CVS Ends Tobacco Sales February 21, 2014 » More American Lung ...

432

The social norms and beliefs of teenage male electronic cigarette use.  

PubMed

Electronic cigarettes (e-cigarettes) are novel, battery-operated inhalation devices that provide warm, vaporized nicotine, and often propylene glycol, to users without the inclusion of tobacco smoke. Because men, in general, are more likely to use cigarettes and illicit drugs than women, a qualitative study was undertaken to investigate the beliefs and perceived social norms regarding this issue among 47 teenage boys who self-identified themselves as current e-cigarette smokers. The majority of respondents reported that they used e-cigarettes because of expeditious consumption and concealment. Furthermore, the most common places respondents self-reported using e-cigarettes were everywhere, in school bathrooms, at home, and in school staircases. Interestingly, respondents stated that e-cigarettes are popular because they are accessible, healthier than tobacco cigarettes, and more aesthetically pleasing. Because of the growing popularity and uncertainty regarding the social and physical consequences of e-cigarettes, this study shows a need for additional research discovery. PMID:24215223

Peters, Ronald J; Meshack, Angela; Lin, Mi-Ting; Hill, Mandy; Abughosh, Susan

2013-01-01

433

Vapor phase exsolution as a controlling factor in hydrogen isotope variation in granitic rocks: the Notch Peak granitic stock, Utah  

USGS Publications Warehouse

The Notch Peak granitic stock, western Utah, is comprised of three concentric sequentially intruded rock types, from granite at the rim, to quartz monzonite I, to quartz monzonite II at the core. The ??18O values of whole rocks vary about an average of 9.4 (SMOW), irrespective of the rock type and position relative to contact, suggesting that the three magmas had the same parent. The whole rock ??D values in the stock range from -100 to -55. ??D values increase toward the cores of both quartz monzonite I and quartz monzonite II, resulting in concentric contours. The ??D contours of quartz monzonite II cross-cut those of quartz monzonite I, suggesting little isotopic interaction between these bodies and the absence of a late pervasive fluid phase. There is a positive correlation between ??D values and water content of the samples, where samples from each body define a distinct field. The positive correlation is explained by isotopic fractionation attendant on vapor exsolution from the crystallizing magma. An observed increase in ??D with the degree of chloritization, a trend opposite to that observed in systems where participation of meteoric water has been demonstrated, is the result of subsolidus interaction with the exsolved fluids. These results show that large variations in the hydrogen isotope ratios of a granitoid can arise by exsolution of a vapor phase from the melt on crystallization. In general, magmas with larger modal amount of primary hydrous phases will tend to have higher ??D values than those with small amounts of hydrous phases. Furthermore, the relatively high ??D values of chlorites at Notch Peak confirm the applicability of classical concepts of closed-system deuteric alteration to some granitoid bodies. Thus, meteoric water interaction need not be always invoked to explain hydrogen isotope variation and deuteric alteration in granitoids. ?? 1983.

Nabelek, P. I.; O'Neil, J. R.; Papike, J. J.

1983-01-01

434

Real-Time Optical Monitoring and Simulations of Gas Phase Kinetics in InN Vapor Phase Epitaxy at High Pressure  

NASA Technical Reports Server (NTRS)

Understanding the kinetics of nucleation and coalescence of heteroepitaxial thin films is a crucial step in controlling a chemical vapor deposition process, since it defines the perfection of the heteroepitaxial film both in terms of extended defect formation and chemical integrity of the interface. The initial nucleation process also defines the film quality during the later stages of film growth. The growth of emerging new materials heterostructures such as InN or In-rich Ga(x)In(1-x)N require deposition methods operating at higher vapor densities due to the high thermal decomposition pressure in these materials. High nitrogen pressure has been demonstrated to suppress thermal decomposition of InN, but has not been applied yet in chemical vapor deposition or etching experiments. Because of the difficulty with maintaining stochiometry at elevated temperature, current knowledge regarding thermodynamic data for InN, e.g., its melting point, temperature-dependent heat capacity, heat and entropy of formation are known with far less accuracy than for InP, InAs and InSb. Also, no information exists regarding the partial pressures of nitrogen and phosphorus along the liquidus surfaces of mixed-anion alloys of InN, of which the InN(x)P(1-x) system is the most interesting option. A miscibility gap is expected for InN(x)P(1-x) pseudobinary solidus compositions, but its extent is not established at this point by experimental studies under near equilibrium conditions. The extension of chemical vapor deposition to elevated pressure is also necessary for retaining stoichiometric single phase