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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

Policy #3220 Policy on the Use of Tobacco and Smoking-Related Products and Electronic Cigarettes and Vaporizers 1  

E-print Network

Policy #3220 ­ Policy on the Use of Tobacco and Smoking-Related Products and Electronic Cigarettes-RELATED PRODUCTS AND ELECTRONIC CIGARETTES AND VAPORIZERS Responsible Oversight Executive: Vice President's restrictions on the use of tobacco and smoking-related products and electronic cigarettes and vaporizers. B

3

Vapor phase SAW immunoassay sensors  

Microsoft Academic Search

In this paper, we present the results of a series of experiments demonstrating real-time vapor phase detection of cocaine molecules using immunosensors based on surface acoustic wave (SAW) resonators.

D. D. Stubbs; Sang-Hun Lee; W. D. Hunt

2002-01-01

4

Vapor Phase Catalytic Ammonia Reduction  

NASA Technical Reports Server (NTRS)

This paper discusses the development of a Vapor Phase Catalytic Ammonia Reduction (VPCAR) teststand and the results of an experimental program designed to evaluate the potential of the technology as a water purification process. In the experimental program the technology is evaluated based upon product water purity, water recovery rate, and power consumption. The experimental work demonstrates that the technology produces high purity product water and attains high water recovery rates at a relatively high specific power consumption. The experimental program was conducted in 3 phases. In phase I an Igepon(TM) soap and water mixture was used to evaluate the performance of an innovative Wiped-Film Rotating-Disk evaporator and associated demister. In phase II a phenol-water solution was used to evaluate the performance of the high temperature catalytic oxidation reactor. In phase III a urine analog was used to evaluate the performance of the combined distillation/oxidation functions of the processor.

Flynn, Michael T.; Harper, Lynn D. (Technical Monitor)

1994-01-01

5

Application of headspace solid phase microextraction to qualitative and quantitative analysis of tobacco additives in cigarettes  

Microsoft Academic Search

Cigarettes may contain up to 10% by weight additives which are intended to make them more attractive. A fast and rugged method for a cigarette-screening for additives with medium volatility was developed using automatic headspace solid phase microextraction (HS-SPME) with a 65?m carbowax-divinylbenzene fiber and gas chromatography–mass spectrometry (GC–MS) with standard electron impact ionisation. In three runs, each cigarette sample

Careen Merckel; Fritz Pragst; Astrid Ratzinger; Beat Aebi; Werner Bernhard; Frank Sporkert

2006-01-01

6

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 PMID:22230844

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

2012-01-01

7

Vapor phase lubrication of high temperature alloys  

SciTech Connect

In a previous study, it was found that when a nickel-based superalloy IN750 was heated to high temperatures, a passive layer of aluminum oxide formed on the surface, preventing vapor phase lubrication. In this study, two nickel-chrome-iron alloys and a nickel-copper alloy were studied for high temperature lubrication to see if these alloys, which contained small amounts of aluminum, would exhibit similar behavior. It was found that under static conditions, all three alloys formed a lubricious nodular coating when exposed to a vapor of aryl phosphate. Under dynamic sliding conditions at 500{degrees}C, these alloys were successfully lubricated with a coefficient of friction of 0.1 and no detectable wear. In order to explain these results, a direct correlation between successful vapor phase lubrication and the composition of the alloys containing aluminum has been proposed. If the ratio of copper/aluminum or iron/aluminum is greater that 100 vapor phase, lubrication will be successful. If the ratio is less than 10, a passive aluminum oxide layer will prevent vapor phase lubrication. By selecting alloys with a high iron or copper content, vapor phase lubrication can provide excellent lubrication at high temperatures. 14 refs., 11 figs., 1 tab.

Hanyaloglu, B.F.; Graham, E.E.; Oreskovic, T.; Hajj, C.G. [Cleveland State Univ., OH (United States)

1995-06-01

8

A Simple and Rapid Method for Standard Preparation of Gas Phase Extract of Cigarette Smoke  

PubMed Central

Cigarette smoke consists of tar and gas phase: the latter is toxicologically important because it can pass through lung alveolar epithelium to enter the circulation. Here we attempt to establish a standard method for preparation of gas phase extract of cigarette smoke (CSE). CSE was prepared by continuously sucking cigarette smoke through a Cambridge filter to remove tar, followed by bubbling it into phosphate-buffered saline (PBS). An increase in dry weight of the filter was defined as tar weight. Characteristically, concentrations of CSEs were represented as virtual tar concentrations, assuming that tar on the filter was dissolved in PBS. CSEs prepared from smaller numbers of cigarettes (original tar concentrations ?15 mg/ml) showed similar concentration-response curves for cytotoxicity versus virtual tar concentrations, but with CSEs from larger numbers (tar ?20 mg/ml), the curves were shifted rightward. Accordingly, the cytotoxic activity was detected in PBS of the second reservoir downstream of the first one with larger numbers of cigarettes. CSEs prepared from various cigarette brands showed comparable concentration-response curves for cytotoxicity. Two types of CSEs prepared by continuous and puff smoking protocols were similar regarding concentration-response curves for cytotoxicity, pharmacology of their cytotoxicity, and concentrations of cytotoxic compounds. These data show that concentrations of CSEs expressed by virtual tar concentrations can be a reference value to normalize their cytotoxicity, irrespective of numbers of combusted cigarettes, cigarette brands and smoking protocols, if original tar concentrations are ?15 mg/ml. PMID:25229830

Higashi, Tsunehito; Mai, Yosuke; Noya, Yoichi; Horinouchi, Takahiro; Terada, Koji; Hoshi, Akimasa; Nepal, Prabha; Harada, Takuya; Horiguchi, Mika; Hatate, Chizuru; Kuge, Yuji; Miwa, Soichi

2014-01-01

9

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...

10

Phase-field crystal model with a vapor phase.  

PubMed

Phase-field crystal (PFC) models are able to resolve atomic length scale features of materials during temporal evolution over diffusive time scales. Traditional PFC models contain solid and liquid phases, however many important materials processing phenomena involve a vapor phase as well. In this work, we add a vapor phase to an existing PFC model and show realistic interfacial phenomena near the triple point temperature. For example, the PFC model exhibits density oscillations at liquid-vapor interfaces that compare favorably to data available for interfaces in metallic systems from both experiment and molecular-dynamics simulations. We also quantify the anisotropic solid-vapor surface energy for a two-dimensional PFC hexagonal crystal and find well-defined step energies from measurements on the faceted interfaces. Additionally, the strain field beneath a stepped interface is characterized and shown to qualitatively reproduce predictions from continuum models, simulations, and experimental data. Finally, we examine the dynamic case of step-flow growth of a crystal into a supersaturated vapor phase. The ability to model such a wide range of surface and bulk defects makes this PFC model a useful tool to study processing techniques such as chemical vapor deposition or vapor-liquid-solid growth of nanowires. PMID:24032965

Schwalbach, Edwin J; Warren, James A; Wu, Kuo-An; Voorhees, Peter W

2013-08-01

11

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

12

Vapor-liquid phase separator studies  

SciTech Connect

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.

1983-10-01

13

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

14

Selective Detection of Vapor Phase Hydrogen Peroxide with Phthalocyanine Chemiresistors  

E-print Network

Selective Detection of Vapor Phase Hydrogen Peroxide with Phthalocyanine Chemiresistors Forest I and toxicity (OSHA PEL ) 1 ppm), vapor phase monitoring of hydrogen peroxide (H2O2) is also an important, California 92093 Received November 14, 2007; E-mail: wtrogler@ucsd.edu Vapor phase monitoring of peroxides

Kummel, Andrew C.

15

Vapor phase lubrication of high temperature alloys  

Microsoft Academic Search

In a previous study, it was found that when a nickel-based superalloy IN750 was heated to high temperatures, a passive layer of aluminum oxide formed on the surface, preventing vapor phase lubrication. In this study, two nickel-chrome-iron alloys and a nickel-copper alloy were studied for high temperature lubrication to see if these alloys, which contained small amounts of aluminum, would

B. F. Hanyaloglu; E. E. Graham; T. Oreskovic; C. G. Hajj

1995-01-01

16

Vapor-phase heat-transport system  

SciTech Connect

A vapor-phase heat-transport system is being tested in one of the passive test cells at Los Alamos. The system consists of one selective-surface collector and a condenser inside a water storage tank. The refrigerant, R-11, can be returned to the collector by gravity or with a pump. Results from several operating configurations are presented, together with a comparison with other passive systems. A new self-pumping concept is presented.

Hedstrom, J.C.

1983-01-01

17

Vapor-liquid phase separator studies  

NASA Technical Reports Server (NTRS)

A study of porous plug use for vapor-liquid phase seperation in spaceborne cryogenic systems was conducted. The three main topics addressed were: (1) the usefulness of porous media in designs that call for variable areas and flow rates; (2) the possibility of prediction of main parameters of porous plugs for a given material; and (3) prediction of all parameters of the plug, including secondary parameters.

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

1985-01-01

18

MODELLING AND SIMULATION OF LIQUID-VAPOR PHASE TRANSITION  

E-print Network

, (,) div(q) heat transfert. (,) P pressure law. G. Faccanoni DNS OF LIQUIDE-VAPOR PHASE TRANSITION 5 / 20, (,) div(q) heat transfert. (,) P pressure law. G. Faccanoni DNS OF LIQUIDE-VAPOR PHASE TRANSITION 5 / 20 =T s > 0 pressure, g def = +P -T s free enthalpy (Gibbs potential). G. Faccanoni DNS OF LIQUIDE-VAPOR

Helluy, Philippe

19

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

20

Toxicological assessment of kretek cigarettes: Part 1: Background, assessment approach, and summary of findings.  

PubMed

This publication introduces a series of six other publications describing the toxicological assessment of kretek cigarettes, i.e., cigarettes characterized primarily by the use of a significant amount of cloves as an ingredient added to the tobacco. This paper presents background information on kretek cigarettes, describes the general approach of the in vitro and in vivo toxicological assessment of mainstream smoke from kretek cigarettes, presents the methodology used, and summarizes the results of the assessment program. In summary, the smoke from kretek cigarettes gives rise to the typical cigarette smoke-related effects known from American-blended cigarettes, does not reveal any novel toxicity, and exhibits an unexpected distinct attenuation of pulmonary inflammation. Based on equal amounts of smoke total particulate matter (TPM), kretek cigarettes deliver less toxicants when compared to American-blended cigarettes; when assessed in vitro, the smoke from kretek cigarettes is less cytotoxic (gas/vapor phase) and less mutagenic (TPM). When assessed in vivo, kretek cigarette smoke shows lower toxicity in the respiratory tract. When based on an equal nicotine basis, several of the toxicity endpoints in kretek cigarettes become equivalent to American-blended cigarettes. The data do not indicate an increased hazard potential of kreteks compared to American-blended cigarettes. PMID:25498000

Roemer, E; Dempsey, R; Schorp, M K

2014-12-01

21

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

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.

1990-01-01

23

Enhancement of epitaxial lateral overgrowth by vapor-phase diffusion  

E-print Network

heterostructure lasers, electroadsorption modulators, light-emitting diodes, etc. [1,2]. Micrometer nanostructures by MBE [10­12]. The advances in experimental field of SAG stimulate the interest in fundamental growth mechanism and ignore diffusion in vapor phase; the effect of vapor phase is reduced

Khenner, Mikhail

24

Chiroptical Spectroscopy in the Vapor Phase  

NASA Astrophysics Data System (ADS)

Electromagnetic radiation propagating through an isotropic chiral medium experiences a complex index of refraction that differs in both real (in-phase) and imaginary (in-quadrature) parts for the right-circular and left-circular polarization states that define the helicity basis. The resulting phenomena of circular birefringence (CB) and circular dichroism (CD) lead to observable effects in the form of dispersive rotation and absorptive elliptization for an impinging beam of plane-polarized light, which commonly are measured under conditions of nonresonant and resonant excitation, respectively. This talk will discuss ongoing efforts designed to elucidate the provenance of electronic optical activity under complementary solvated and isolated conditions, with the latter vapor-phase work made possible by our continuing development of Cavity Ring-Down Polarimetry (CRDP). Molecules of interest include the rigid bicyclic ketone (1R,4R)-norbornenone, where the spatial arrangement of distal alkene and carbonyl moeities gives rise to extraordinarily large specific rotation (CB) parameters that are predicted incongruously by different quantum-chemical methods; the monoterpene constitutional isomers (S)-2-carene and (S)-3-carene, which display surprisingly distinct chiroptical properties; and conjugated ketones such as (S)-verbenone, where CD probes of weak ?*?n absorption bands have been performed at vibronic resolution. The disparate nature of gas-phase and condensed-phase optical activity will be highlighted, with complementary ab initio calculations serving to elucidate the structural, chemical, and electronic origins of observed behavior. T. Müller, K. B. Wiberg, P. H. Vaccaro, J. R. Cheeseman, and M. J. Frisch, J. Opt. Soc. Am. B 19, 125 (2002) P. H. Vaccaro, ``Chapter 1.II.10: Optical Rotation and Intrinsic Optical Activity'' in Comprehensive Chiroptical Spectroscopy, N. Berova, P. L. Polavarapu, K. Nakanishi, and R. W. Woody, eds. (John Wiley and Sons, Inc., Hoboken, NJ, 2011).

Lahiri, Priyanka; Long, Benjamin D.; Wiberg, Kenneth B.; Vaccaro, Patrick H.

2011-06-01

25

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

26

Vapor-phase viscosity of phenol  

NASA Astrophysics Data System (ADS)

New measurements of the vapor-phase viscosity of phenol were performed from 437 up to 624 K and for densities between 0.006 and 0.023 mol · L-1 in an all-quartz oscillating-disk viscometer with small gaps. Thus, including our own measurements reported earlier, experimental data are available in the temperature range between 376 and 639 K and in the density range from 0.001 up to 0.023 mol · L-1. The data were evaluated with a density series for the viscosity in which only a linear density contribution is included. The values of the second viscosity virial coefficient obtained for phenol as well as for benzene, toluene, and p-xylene were compared with results of the Rainwater-Friend theory and of the modified Enskog theory on the basis of the Lennard-Jones 12-6 potential. The agreement is reasonable, when the potential parameter ratios determined by Bich and Vogel are used. The influence of bound dimers seems to be already taken into account in the three-monomer contribution according to Hoffman and Curtiss.

Vogel, E.; Neumann, A.-K.

1993-07-01

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

Early specific free radical-related cytotoxicity of gas phase cigarette smoke and its paradoxical temporary inhibition by tar  

Microsoft Academic Search

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

Marcel Culcasi; Agnès Muller; Anne Mercier; Jean-Louis Clément; Olivier Payet; Antal Rockenbauer; Véronique Marchand; Sylvia Pietri

2006-01-01

29

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

30

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

31

FIELD TRAPPING OF SUBSURFACE VAPOR PHASE PETROLEUM HYDROCARBONS  

EPA Science Inventory

Soil gas samples from intact soil cores were collected on adsorbents at a field site, then thermally desorbed and analyzed by laboratory gas chromatography (GC). ertical concentration profiles of predominant vapor phase petroleum hydrocarbons under ambient conditions were obtaine...

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

Preliminary assessment of halogenated alkanes as vapor-phase tracers  

SciTech Connect

New tracers are needed to evaluate the efficiency of injection strategies in vapor-dominated environments. One group of compounds that seems to meet the requirements for vapor-phase tracing are the halogenated alkanes (HCFCs). HCFCs are generally nontoxic, and extrapolation of tabulated thermodynamic data indicate that they will be thermally stable and nonreactive in a geothermal environment. The solubilities and stabilities of these compounds, which form several homologous series, vary according to the substituent ratios of fluorine, chlorine, and hydrogen. Laboratory and field tests that will further define the suitability of HCFCs as vapor-phase tracers are under way.

Adams, Michael C.; Moore, Joseph N.; Hirtz, Paul

1991-01-01

34

External fuel vaporization study, phase 2  

NASA Technical Reports Server (NTRS)

An analytical study was conducted to evaluate the effect of variations in fuel properties on the design of an external fuel vaporizaton system. The fuel properties that were considered included thermal stability, critical temperature, enthalpy a critical conditions, volatility, and viscosity. The design parameters that were evaluated included vaporizer weight and the impact on engine requirement such as maintenance, transient response, performance, and altitude relight. The baseline fuel properties were those of Jet A. The variation in thermal stability was taken as the thermal stability variation for Experimental Referee Broad Specification (ERBS) fuel. The results of the analysis indicate that a change in thermal stability equivalent to that of ERBS would increase the vaporization system weight by 20 percent, decrease oprating time between cleaning by 40 percent and make altitude relight more difficult. An increase in fuel critical temperature of 39 K would require a 40 percent increase in vaporization system weight. The assumed increase in enthalpy and volatility would also increase vaporizer weight by 40 percent and make altitude relight extremely difficult. The variation in fuel viscosity would have a negligible effect on the design parameters.

Szetela, E. J.; Chiappetta, L.

1981-01-01

35

Phase transformations during the growth of paracetamol crystals from the vapor phase  

NASA Astrophysics Data System (ADS)

Phase transformations during the growth of paracetamol crystals from the vapor phase are studied by differential scanning calorimetry. It is found that the vapor-crystal phase transition is actually a superposition of two phase transitions: a first-order phase transition with variable density and a second-order phase transition with variable ordering. The latter, being a diffuse phase transition, results in the formation of a new, "pretransition," phase irreversibly spent in the course of the transition, which ends in the appearance of orthorhombic crystals. X-ray diffraction data and micrograph are presented.

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

2014-07-01

36

Quantitative Infrared Spectra of Vapor Phase Chemical Agents  

SciTech Connect

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).

Sharpe, Steven W.; Johnson, Timothy J.; Chu, P M.; Kleimeyer, J; Rowland, Brad; Gardner, Patrick J.

2003-04-21

37

Vapor phase release of silicon nanostructures for optomechanics application  

Microsoft Academic Search

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

Parag B. Deotare; Mughees Khan; Marko Loncar

2009-01-01

38

Growth of gallium nitride by hydride vapor-phase epitaxy  

Microsoft Academic Search

This paper reviews the growth of GaN thick films by hydride vapor-phase epitaxy (HVPE). Emphasis is placed on recent developments, including the growth of nondegenerate material, characterization of film properties and suitability of such films for epitaxial device overgrowths. Films up to 74 ?m thick have been deposited on sapphire substrates with no evidence of thermally induced cracking and a

R. J. Molnar; W. Götz; L. T. Romano; N. M. Johnson

1997-01-01

39

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

40

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

41

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

Microsoft Academic Search

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

Christopher R. E. Coggins; Charles L. Gaworski

2008-01-01

42

Graphene oxide bound silica for solid-phase extraction of 14 polycyclic aromatic hydrocarbons in mainstream cigarette smoke.  

PubMed

Polycyclic aromatic hydrocarbons (PAHs) were considered as a source of carcinogenicity in mainstream cigarette smoke (MSS). Accurate quantification of these components was necessary for assessing public health risk. In our study, a solid-phase extraction (SPE) method using graphene oxide (GO) bound silica as adsorbent for purification of 14 PAHs in MSS was developed. During SPE process, large matrices interferences of MSS were adsorbed on SPE column. The result of FTIR spectra demonstrated that these matrices interferences were adsorbed on GO mainly through OH and CO groups. The concentrations of PAHs in MSS extract were determined by gas chromatography-mass spectrometry (GC-MS). The limit of detection (LOD) and limit of quantification (LOQ) of the developed method for 14 PAHs ranged from 0.05 to 0.36ng/cig and 0.17 to 1.19ng/cig, respectively. The accuracy of the measurement of 14 PAHs was from 73 to 116%. The relative standard deviations of intra- and inter-day analysis were less than 7.8% and 13.9%, respectively. Moreover, the developed method was successfully applied for analysis of real cigarette containing 1R5F reference cigarette and 12 top-selling commercial cigarettes in China. PMID:25512123

Shi, Rui; Yan, Lihong; Xu, Tongguang; Liu, Dongye; Zhu, Yongfa; Zhou, Jun

2015-01-01

43

Comparative characterization of organic emissions from diesel particles, coke oven mains, roofing tar vapors and cigarette smoke condensate.  

PubMed

This paper reports the characterization of the extractable organics from diesel particulate emissions compared to other complex organics which have been reported to increase the risk of human lung cancer. Class fractions of diesel, cigarette smoke condensate, roofing tar, and coke oven extracts were obtained using liquid/liquid partitioning and silica gel chromatography. Capillary GC/MS was used to identify compounds in each extract fraction. This manuscript reports the mass distribution after fractionation of each extract, all identified fraction components and quantification of selected mutagenic and carcinogenic compounds. PMID:3804556

Williams, R; Sparacino, C; Petersen, B; Bumgarner, J; Jungers, R H; Lewtas, J

1986-01-01

44

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

45

Supported complex catalysts for vapor-phase carbonylations  

SciTech Connect

Supported mixed bidentate rhodium and iridium complexes derived from phosphonate-phosphanes have been studied in methanol carbonylation and in ethylene hydroformylation. The complexes showed higher activities than bis-phosphane complexes in homogeneous and vapor-phase methanol carbonylation. Hemilabile behavior of the mixed bidentate complexes may explain these findings. In contrast to strongly chelating ligands, phosphonate-phosphane ligands improved the selectivity of supported rhodium complexes in ethylene hydroformylation. Mixed zirconium phosphonate structures containing phosphane groups afforded excellent heterogeneous rhodium complex catalysts. The zirconium phosphonate-phosphane-rhodium catalysts were several times more active than rhodium on silica or rhodium on activated carbon, showed a superior stability, and produced butyraldehydes with up to 96% selectivity in the vapor-phase hydroformylation of propylene.

Bischoff, S.; Weigt, A.; Kant, M.; Schuelke, U. [Institute for Applied Chemistry Berlin-Adlershof (Germany)] [and others

1996-10-01

46

Growth of Zinc Oxide Single Crystals by Vapor Phase Reaction  

Microsoft Academic Search

ZnO single crystals are grown by vapor phase reaction with ZnI2 source. When the growth region is maintained between 1150°C and 1200°C, crystals grow by oxidation, and between 970°C and 1020°C, by hydrolysis. Crystals are mainly needles 15 mm in length or plates 8 mm2 in area. Patterns suggesting their growth mechanisms are observed in their microphotographs. The present experiments

Masami Hirose

1971-01-01

47

PROCESSES AFFECTING FREE-PHASE HYDROCARBON REMOVAL BY VAPOR EXTRACTION  

Microsoft Academic Search

A laboratory-scale soil vapor extraction test was conducted to evaluate the mechanisms that affect removal of subsurface free-phase hydrocarbon. The test was performed inside a steel-reinforced acrylic tank, 185 cm long by 185 cm high by 25 cm wide, which was filled with #60 industrial grade silica sand. A gradient-driven water table was established to simulate a field groundwater system.

Robert J. Frank; David Huntley

48

The influence of prestrained metalorganic vapor phase epitaxial gallium-nitride templates on hydride vapor phase epitaxial growth  

NASA Astrophysics Data System (ADS)

We have varied the strain situation in metalorganic vapor phase epitaxial (MOVPE) grown gallium-nitride (GaN) by exchanging the nucleation layer and by inserting a submono-SixNy-interlayer in the first few hundred nanometers of growth on sapphire substrates. The influence on the MOVPE template and subsequent hydride vapor phase epitaxial (HVPE) growth could be shown by in-situ measurements of the sample curvature. Using the results of these investigations, we have established a procedure to confine the curvature development in MOVPE and HVPE growth to a minimum. By increasing the layer thickness in HVPE, we could create self-separated, freestanding GaN layers with small remaining curvature.

Klein, M.; Meisch, T.; Lipski, F.; Scholz, F.

2014-09-01

49

WHAT ARE E-CIGARETTES? Electronic cigarettes, also called electronic nicotine delivery systems (ENDS), are designed to mimic the size,  

E-print Network

WHAT ARE E-CIGARETTES? Electronic cigarettes, also called electronic nicotine delivery systems · There have been no national prevalence studies. The Tobacco Vapor Electronic Cigarette Association claims (ENDS), are designed to mimic the size, shape, and use of a conventional cigarette. A battery powers

Su, Xiao

50

Vapor-phase epitaxy of high-crystallinity GaN films using Ga 2O vapor and NH 3  

NASA Astrophysics Data System (ADS)

In this study, vapor-phase epitaxy (VPE) of GaN oriented-film was performed using Ga 2O vapor as the Ga source. Ga 2O vapor was obtained by reducing Ga 2O 3 powder with H 2 gas at 1000 °C. The Ga 2O vapor was then reacted with NH 3 on a seed substrate at 1100-1150 °C. A high quality GaN substrate (1 mm thick, with full widths at half maximum of GaN (0 0 0 2) X-ray rocking curve of 107-110 arcsec) prepared by the Na-flux method were used as the seed substrate. After 30 min of growth, a 3-?m flat GaN (0 0 0 1) epitaxial layer was grown on the seed substrate. X-ray diffraction (XRD) measurements showed that the FWHM of the GaN epitaxial layer was 74-111 arcsec, showing high crystallinity. Secondary ion mass spectrometry (SIMS) analysis showed that the oxygen concentration in the epitaxial layer was 1.5×10 18 atoms/cm 3. Although an oxide was used as the raw material, oxygen concentration close to those in GaN crystal grown by the hydride vapor phase epitaxy (HVPE) and metalorganic vapor phase epitaxy (MOVPE) were achieved. We concluded that the VPE method using Ga 2O vapor has potential as a simple vapor-phase-growing technique for high-quality GaN films.

Imade, Mamoru; Kishimoto, Hiroki; Kawamura, Fumio; Yoshimura, Masashi; Kitaoka, Yasuo; Sasaki, Takatomo; Mori, Yusuke

2010-02-01

51

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

52

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 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 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

2014-10-01

53

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. Fast pyrometry technique was used to determine velocity of expansion, pressure and temperature nearby metal - gas boundary. Heating of material under research on the boundary with hot shocked gas at a constant final pressure of material expansion is another source of high temperature states. Optically transparent or translucent shocked helium and neon give the possibility to achieve temperatures and pressures exceeding critical parameters of tungsten- one of the most refractory metals. Intensive heat and mass transfer on the boundary give the opportunity to investigate states not only near binodal but also liquid spinodal. Experimental results and issues of such investigation with lead, tin, nickel, and tungsten is analyzed in the proposed paper.

Ternovoi, Vladimir; Filimonov, Aleksandr; Fortov, Vladimir; Gordon, Yulyi; Nikolaev, Dmitry; Pyalling, Alexei

1999-06-01

54

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

55

EPR study of the toxicological effects of gas-phase cigarette smoke and the protective effects of grape seed extract on the mitochondrial membrane  

Microsoft Academic Search

Electron paramagnetic resonance spin trapping and spin labeling techniques were used to study the effects of grape seed extract\\u000a on the biophysical propertiers of the mitochondrial membrane exposed to gas-phase cigarette smoke. The spin trapping results\\u000a indicated that grape seed extract can effectively scavenge free radicals in cigarette smoke and the lipid free radicals generated\\u000a from the lipid peroxidation of

J. Gao; H. Tang; Y. Li; H. Liu; B. Zhao I

2002-01-01

56

Vapors-liquid phase separator. [infrared telescope heat sink  

NASA Technical Reports Server (NTRS)

The use of porous plugs, mostly with in the form of passive devices with constant area were considered as vapor-liquid phase separators for helium 2 storage vessels under reduced gravity. The incorporation of components with variable cross sectional area as a method of flow rate modification was also investigated. A particular device which uses a shutter-type system for area variation was designed and constructed. This system successfully permitted flor rate changes of up to plus or minus 60% from its mean value.

Frederking, T. H. K.; Brown, G. S.; Chuang, C.; Kamioka, Y.; Kim, Y. I.; Lee, J. M.; Yuan, S. W. K.

1980-01-01

57

Modeling of Gallium Nitride Hydride Vapor Phase Epitaxy  

NASA Technical Reports Server (NTRS)

A reactor model for the hydride vapor phase epitaxy of GaN is presented. The governing flow, energy, and species conservation equations are solved in two dimensions to examine the growth characteristics as a function of process variables and reactor geometry. The growth rate varies with GaCl composition but independent of NH3 and H2 flow rates. A change in carrier gas for Ga source from H2 to N2 affects the growth rate and uniformity for a fixed reactor configuration. The model predictions are in general agreement with observed experimental behavior.

Meyyappan, Meyya; Arnold, James O. (Technical Monitor)

1997-01-01

58

Effect of dimensionality on vapor-liquid phase transition  

SciTech Connect

Dimensionality play significant role on ‘phase transitions’. Fluids in macroscopic confinement (bulk or 3-Dimensional, 3D) do not show significant changes in their phase transition properties with extent of confinement, since the number of molecules away from the surrounding surfaces is astronomically higher than the number of molecules in close proximity of the confining surfaces. In microscopic confinement (quasi 3D to quasi-2D), however, the number of molecules away from the close proximity of the surface is not as high as is the case with macroscopic (3D) confinement. Hence, under the same thermodynamic conditions ‘phase transition’ properties at microscopic confinement may not remain the same as the macroscopic or 3D values. Phase transitions at extremely small scale become very sensitive to the dimensions as well as the surface characteristics of the system. In this work our investigations reveal the effect of dimensionality on the phase transition from 3D to quasi-2D to 2D behavior. We have used grand canonical transition matrix Monte Carlo simulation to understand the vapor–liquid phase transitions from 3D to quasi-2D behavior. Such studies can be helpful in understanding and controlling the fluid film behaviour confined between solid surfaces of few molecular diameters, for example, in lubrication applications.

Singh, Sudhir Kumar, E-mail: sksingh@thapar.edu [Department Chemical Engineering, Thapar University, Patiala-147004 Punjab (India)

2014-04-24

59

Effect of dimensionality on vapor-liquid phase transition  

NASA Astrophysics Data System (ADS)

Dimensionality play significant role on `phase transitions'. Fluids in macroscopic confinement (bulk or 3-Dimensional, 3D) do not show significant changes in their phase transition properties with extent of confinement, since the number of molecules away from the surrounding surfaces is astronomically higher than the number of molecules in close proximity of the confining surfaces. In microscopic confinement (quasi 3D to quasi-2D), however, the number of molecules away from the close proximity of the surface is not as high as is the case with macroscopic (3D) confinement. Hence, under the same thermodynamic conditions `phase transition' properties at microscopic confinement may not remain the same as the macroscopic or 3D values. Phase transitions at extremely small scale become very sensitive to the dimensions as well as the surface characteristics of the system. In this work our investigations reveal the effect of dimensionality on the phase transition from 3D to quasi-2D to 2D behavior. We have used grand canonical transition matrix Monte Carlo simulation to understand the vapor-liquid phase transitions from 3D to quasi-2D behavior. Such studies can be helpful in understanding and controlling the fluid film behaviour confined between solid surfaces of few molecular diameters, for example, in lubrication applications.

Singh, Sudhir Kumar

2014-04-01

60

Debris cloud characterization in the liquid-vapor phase  

SciTech Connect

A series of experiments has been performed on the Sandia Hypervelocity Launcher to impact a 1.25-mm thick aluminum bumper by an aluminum flier plate 17-mm diameter by 0.92-mm thick over the velocity range of 5 km/s to 11 km/s. Radiographic techniques were employed to record the debris cloud generated upon impact. The shape of the debris cloud is found to depend on the flier plate tilt. Generally the data indicate a central core of higher density surrounded by a diffused layer. These experiments allow measurements of debris cloud expansion velocities as the material undergoes a phase change from solid fragments at impact velocities of 5 km/s to a mixture of liquid and vapor phase at higher impact velocities. The expansion velocity of the debris cloud increases with increasing impact velocity, with the high-density leading edge traveling faster than the impact velocity. There is a difference between the X-ray and photographic measurements of expansion velocities at higher impact velocities. This is believed to be due to the presence of very low- density vapor in the photographic records that are not detected using X-ray techniques.

Chhabildas, L.C.; Boslough, M.B.; Reinhart, W.D.; Hall, C.A.

1993-10-01

61

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

62

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

Microsoft Academic Search

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

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

2008-01-01

63

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

64

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

65

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

66

Vapor phase lubrication of a Ni-based superalloy  

SciTech Connect

In addition to ceramics, alloys such as tool steel and nickel- and iron-based superalloys are being considered for high temperature applications such as missile bearings and low heat rejection engines. Studies were made to lubricate a nickel-based superalloy at 500{degrees}C, by using a vaporized aryl phosphate ester, at a concentration of 0.1% in air. From deposition and wear studies it was found that it was impossible to form a good polymeric coating on the superalloy surface. Energy dispersive X-ray analyzer (EDXA) analysis showed that this was due to minute quantities of aluminum in the alloy segregating to the surface, upon being heated to 500{degrees}C, forming a passive oxide coating. It was necessary to activate the surface, in order to lubricate the material successfully. A method of activation by electrodepositing the surface with a layer of iron oxide was developed. Once activated, a good lubricous polymer was formed on the superalloy surface. Tests performed under dynamic conditions and 1 MPa pressure, using an activated specimen surface showed no wear and a coefficient of friction ({mu}) of 0.05. These results stress the importance of material selection for high temperature vapor phase lubrication. 15 refs., 13 figs., 2 tabs.

Hanyaloglu, B.; Fedor, D.C.; Graham, E.E. [Cleveland State Univ., OH (United States)

1995-03-01

67

Quantitative Infrared Spectra of Vapor Phase Chemical Agents  

SciTech Connect

Quantitative, moderately high resolution (0.1 cm-1) infrared spectra have been acquired for a number of nitrogen broadened (1 atm 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 Cell1 of 5.6 meter 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 Dugway proving Grounds (DPG).

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

2003-08-01

68

Vapor-phase molar Kerr constant values from solution measurements  

NASA Astrophysics Data System (ADS)

A method is proposed for determination of molar Kerr constants (mK) by extrapolation of the values measured in a series of selected solvents. The mK values of 19 organic compounds were calculated. Most of the compounds cannot be studied in the vapor phase. The discrete-continuum solvation model was applied to investigate the influence of solvent nature on solubility of the compounds under investigation. It is shown that universal interactions between the solvent and solute molecules, including the dispersive, inductive, and dipole-dipole interactions, dominate the solvation process. The optimum model of internal field was chosen to determine the Kerr constant. The values of mKgas measured experimentally coincide with the values of mK??=0? that were obtained by extrapolation of mK?. Hence, this method can be applied to calculate the values of molar Kerr constants on the basis of measurements in solutions.

Prezhdo, Victor; Olan, Karol; Prezhdo, Oleg; Zubkova, Valentina

2015-01-01

69

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

70

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

71

Low Pressure Metal-Organic Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

A comprehensive investigation of ZnCdS grown on GaAs by the low pressure metal-organic vapor phase epitaxy (MOVPE) technique has been conducted. Optimization, growth characteristics, film properties, solid-vapor equilibrium and device applications are key issues that have been addressed. The Taguchi method or design of experiments (DOE) approach is taken to determine the effects of process parameters on the crystalline quality of epilayers. Its main advantage over the standard methodology of changing one-factor-at -a-time is the reduction of experimental runs needed to obtain the same precision of information. In addition, DOE can statistically evaluate significance of multi-parameter interactions. Thin ZnCdS films have been grown on (100) and (111) oriented GaAs substrates using diethyl zinc (DEZn), dimethyl cadmium (DMCd) and H_2S. The lowest reported full width at half maximum of peaks obtained from X-ray diffraction spectra has been obtained using this chemistry. Critical process parameters and their setpoints have also been identified that influence the desirable 2-dimensional and undesirable 3-dimensional growth. A nucleation/growth mechanism is presented to explain the preferential initiation of one growth mode over the other. Other growth characteristics including flow mechanics, film thickness uniformity, defect density, crystal structure, solid phase composition and optical purity have been studied as a function of growth parameters. The general growth characteristics highly influence the optical, physical and electrical properties of ZnCdS. The bandgap energy and complex refractive index have been measured by reflectometry and ellipsometry, respectively. Thermal expansion coefficients have been calculated from lattice constant changes at various temperatures. In-situ doping studies have also been performed to determine the maximum electron and hole concentrations. A simple model based on the regular solution approach was developed to explain the solid-vapor equilibrium distribution. For the first time, the interaction parameters for binary II -VI compounds were calculated from Stringfellow's delta lattice parameter model based solely on material properties of II-VI compounds. The results show a good fit to experimental data across a wide range of temperature values. The measured properties of ZnCdS have been used in theoretical calculations of double heterostructure lasers. The complex refractive indices are needed to evaluate the optical confinement of a symmetric three-layer slab waveguide: ZnCdS/ZnSe/ZnCdS. The relationship between the active layer thickness and optical confinement have also been investigated. Bandgap energies along with electron affinities have been used to determine the carrier confinement. Calculations based on photothreshold values confirm these results.

Cho, Joe Sung

72

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

73

Vapors Produced by Electronic Cigarettes and E-Juices with Flavorings Induce Toxicity, Oxidative Stress, and Inflammatory Response in Lung Epithelial Cells and in Mouse Lung  

PubMed Central

Oxidative stress and inflammatory response are the key events in the pathogenesis of chronic airway diseases. The consumption of electronic cigarettes (e-cigs) with a variety of e-liquids/e-juices is alarmingly increasing without the unrealized potential harmful health effects. We hypothesized that electronic nicotine delivery systems (ENDS)/e-cigs pose health concerns due to oxidative toxicity and inflammatory response in lung cells exposed to their aerosols. The aerosols produced by vaporizing ENDS e-liquids exhibit oxidant reactivity suggesting oxidants or reactive oxygen species (OX/ROS) may be inhaled directly into the lung during a “vaping” session. These OX/ROS are generated through activation of the heating element which is affected by heating element status (new versus used), and occurs during the process of e-liquid vaporization. Unvaporized e-liquids were oxidative in a manner dependent on flavor additives, while flavors containing sweet or fruit flavors were stronger oxidizers than tobacco flavors. In light of OX/ROS generated in ENDS e-liquids and aerosols, the effects of ENDS aerosols on tissues and cells of the lung were measured. Exposure of human airway epithelial cells (H292) in an air-liquid interface to ENDS aerosols from a popular device resulted in increased secretion of inflammatory cytokines, such as IL-6 and IL-8. Furthermore, human lung fibroblasts exhibited stress and morphological change in response to treatment with ENDS/e-liquids. These cells also secrete increased IL-8 in response to a cinnamon flavored e-liquid and are susceptible to loss of cell viability by ENDS e-liquids. Finally, exposure of wild type C57BL/6J mice to aerosols produced from a popular e-cig increase pro-inflammatory cytokines and diminished lung glutathione levels which are critical in maintaining cellular redox balance. Thus, exposure to e-cig aerosols/juices incurs measurable oxidative and inflammatory responses in lung cells and tissues that could lead to unrealized health consequences. PMID:25658421

Lerner, Chad A.; Sundar, Isaac K.; Yao, Hongwei; Gerloff, Janice; Ossip, Deborah J.; McIntosh, Scott; Robinson, Risa; Rahman, Irfan

2015-01-01

74

Vapor phase elemental sulfur amendment for sequestering mercury in contaminated soil  

DOEpatents

The process of treating elemental mercury within the soil is provided by introducing into the soil a heated vapor phase of elemental sulfur. As the vapor phase of elemental sulfur cools, sulfur is precipitated within the soil and then reacts with any elemental mercury thereby producing a reaction product that is less hazardous than elemental mercury.

Looney, Brian B.; Denham, Miles E.; Jackson, Dennis G.

2014-07-08

75

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 147 ng/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 24-36 nm. 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

76

Crystallization from a vapor phase in igneous rocks -- A conceptual model  

SciTech Connect

Euhedral, late-stage crystals in pocket pegmatite and in vesicles of volcanic rocks are commonly cited as examples of crystallization from a vapor phase. If, however, crystallization takes place only from the cavity forming vapor, that vapor cannot contain sufficient material for the formation of the observed crystals. The approximate amount of H[sub 2]O vapor and percentage of dissolved silicate matter (1) for shallow pocket pegmatite is 0.5 g/cm[sup 3] and 0.3 percent; (2) for vesicles is 0.002 g/cm[sup 3] and [much lt]1 percent. These values show that the silicate matter dissolved in the vapor is insufficient for the formation of the observed crystals. No (or little) recharge of the vapor is an unstated assumption in most discussions of enclosed cavities. This, however, is not quite correct. For a simplified system, four phases will exist in equilibrium: (1) mineral grains growing from liquid, (2) late-stage, H[sub 2]O-enriched, silicate liquid, (3) vapor, (4) crystals growing from vapor. The total system (for transferal of silicate matter) is given. Little silicate matter is dissolved in the vapor at any one time, but it is replenished as the crystals grow. The vapor becomes a continuously resupplied reservoir of dissolved silicate matter; crystallization from the vapor continues until the silicate liquid is depleted.

Kleck, W.D. (Orange Coast Coll., Costa Mesa, CA (United States))

1993-04-01

77

Vaporization behavior of non-stoichiometric refractory carbide materials and direct observations of the vapor phase using laser diagnostics  

SciTech Connect

Transition metal and actinide carbides, such as ZrC or NbC and UC or ThC, exhibit a wide range of stoichiometry, and therefore vaporize incongruently. At long times, steady state vaporization can be achieved where relative concentrations of atomic species on solid surface equals that in the gas phase. The surface composition under these steady state conditions is termed the congruently vaporizing composition, (CVC). Modeling the vaporization or corrosion behavior of this dynamic process is complex and requires an understanding of how the surface composition changes with time and a knowledge of CVC, which is both temperature and atmosphere dependent. This paper describes vaporization and corrosion behavior of non-stoichiometric refractory carbide materials and, as an example, describes a thermokinetic model that characterizes the vaporization behavior of the complex carbide U{sub x}Zr{sub 1-x}C{sub y} in hydrogen at 2500 to 3200 K. This model demonstrates that steady state corrosion of U{sub x}Zr{sub l-x}C{sub y} is rate limited by gaseous transport of Zr where partial pressure of Zr is determined by CVC. This paper also briefly describes efforts to image and characterize the vapor phase above the surface of ZrC in static and flowing gas environments using planar laser induced fluorescence. We have developed the method for monitoring and controlling the corrosion behavior of nuclear fuels in nuclear thermal rockets. However, the techniques described can be used, to image boundary layers, and could be used verifying corrosion models.

Butt, D.P.; Wantuck, P.J.; Rehse, S.J.; Wallace, T.C. Sr.

1993-09-01

78

Underwater vapor phase burning of aluminum particles and on aluminum ignition during steam explosions  

SciTech Connect

Recently reported experimental studies on aluminum-water steam explosions indicate that there may be a critical metal temperature at which the process changes over from a physical explosion to one which is very violent and involves the rapid liberation of chemical energy. In this report we examine the hypothesis that vapor-phase burning of aluminum is a necessary condition for the occurrence of such ignition-type'' steam explosions. An available two-phase stagnation flow film-boiling model is used to calculate the steam flux to the vaporizing aluminum surface. Combining this calculation with the notion that there is an upper limit to the magnitude of the metal vaporization rate at which the reaction regime must change from vapor phase to surface burning, leads to prediction of the critical metal surface temperature below which vapor phase burning is impossible. The critical temperature is predicted for both the aluminum-water pre-mixture configuration in which coarse drops of aluminum are falling freely through water and for the finely-fragmented aluminum drops in the wake of the pressure shock that triggers'' the explosion. Vapor phase burning is predicted to be possible during the pre-mixture phase but not very likely during the trigger phase of a steam explosion. The implications of these findings in terms of the validity of the hypothesis that ignition may begin with the vapor phase burning of aluminum is discussed. Recently postulated, alternative mechanisms of underwater aluminum ignition are also discussed.

Epstein, M. (Fauske and Associates, Inc., Burr Ridge, IL (United States))

1991-09-01

79

Underwater vapor phase burning of aluminum particles and on aluminum ignition during steam explosions  

SciTech Connect

Recently reported experimental studies on aluminum-water steam explosions indicate that there may be a critical metal temperature at which the process changes over from a physical explosion to one which is very violent and involves the rapid liberation of chemical energy. In this report we examine the hypothesis that vapor-phase burning of aluminum is a necessary condition for the occurrence of such ``ignition-type`` steam explosions. An available two-phase stagnation flow film-boiling model is used to calculate the steam flux to the vaporizing aluminum surface. Combining this calculation with the notion that there is an upper limit to the magnitude of the metal vaporization rate at which the reaction regime must change from vapor phase to surface burning, leads to prediction of the critical metal surface temperature below which vapor phase burning is impossible. The critical temperature is predicted for both the aluminum-water pre-mixture configuration in which coarse drops of aluminum are falling freely through water and for the finely-fragmented aluminum drops in the wake of the pressure shock that ``triggers`` the explosion. Vapor phase burning is predicted to be possible during the pre-mixture phase but not very likely during the trigger phase of a steam explosion. The implications of these findings in terms of the validity of the hypothesis that ignition may begin with the vapor phase burning of aluminum is discussed. Recently postulated, alternative mechanisms of underwater aluminum ignition are also discussed.

Epstein, M. [Fauske and Associates, Inc., Burr Ridge, IL (United States)

1991-09-01

80

Vapor phase deposition of transition metal fluoride glasses  

NASA Astrophysics Data System (ADS)

Multicomponent fluoride glasses in the PbF2-ZnF2-GaF3 (PZG) vitreous ternary system have been prepared by vapor phase deposition. The thermal stability of the deposited glass was improved by adding stabilizing agents (AlF3, NaF, LiF, InF3). The thin films, deposited on different substrates (fluoride glass, fluoride single crystal, metal, and silica glass) have been characterized by x-ray diffraction. Differential scanning calorimetry (DSC) and secondary ion mass spectroscopy (SIMS). The quality of the film, adherence, and homogeneity was controlled by scanning electronic microscopy (SEM). The optical characteristics of the film and PZG glass are given: the visible-infrared (VIS-IR) window is 0.3-8 micrometers and the refractive index 1.59+/- 0.2 depends on the lead content. Mn2+ doped films (up to 3 mole % MnF2) are optically active: Mn2+ exhibits a broad luminescence band at 560-570 nm (orange). The achieved film thickness varies from 0.5 to 80 micrometers , and the refractive index gradient approaches the required geometry for planar waveguides (doping of the film with lanthanides is in progress).

Boulard, Brigitte; Jacoboni, Charles

1991-08-01

81

Liquid-vapor phase diagram of metals using EAM potential  

NASA Astrophysics Data System (ADS)

Pair-wise additive potentials are not adequate to describe the properties of metallic systems since many body effects are completely ignored in that approximation. In this regard, the embedded atom method is more appropriate because, in addition to the pair interaction, the total energy includes an embedding energy which is the energy required to add an impurity atom to the host electron fluid. Thus EAM takes into account the many body effects to some extent. We use the Cai and Ye's EAM potential to predict the liquid vapor phase diagram and critical constants of Aluminum and Copper within a perturbation theory approach. In this method, free energy of a fluid molecule, trapped in a cage formed by its nearest neighbors, is expanded about a hard sphere reference system. The first order correction term is calculated in terms of the zero temperature isotherm of the solid obtained using the EAM potential. Higher order correction terms are added to account for the deviation of the behavior of the real fluid from the reference hard sphere fluid.

Bhattacharya, Chandrani

2013-02-01

82

Zno nanostructures fabricated through a double-tube vapor-phase transport synthesis  

Microsoft Academic Search

A double-tube vapor-phase transport system has been used to synthesize ZnO nanostructures. Nanofeatures of ZnO nanocombs, nanoblades and nanowires were achieved in different temperature zones. The scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to study the nanostructure dependence with temperature. The vapor–liquid–solid (VLS) and vapor–solid (VS) growth mechanism are applied to explain the growth processes. ZnO

Y. X. Chen; M. Lewis; W. L. Zhou

2005-01-01

83

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. PMID:21504917

2011-01-01

84

Electronic Cigarettes  

MedlinePLUS

... liquid mixture typically composed of propylene glycol, vegetable glycerin, flavoring chemicals, and nicotine 1 ( Figure ). E-cigarette ... carcinogens. Users inhale a heated propylene glycol or glycerin-based solution for which there are no long- ...

85

Molecular Orbital Studies of Titanium Nitride Chemical Vapor Deposition: Gas Phase Complex Formation,  

E-print Network

Molecular Orbital Studies of Titanium Nitride Chemical Vapor Deposition: Gas Phase Complex Received June 6, 2000 The chemical vapor deposition (CVD) of titanium nitride can be carried out with TiCl4 Titanium nitride thin films have a variety of proper- ties, such as extreme hardness, high chemical

Schlegel, H. Bernhard

86

Molecular Orbital Studies of Zinc Oxide Chemical Vapor Deposition: Gas-Phase Hydrolysis of Diethyl Zinc,  

E-print Network

region.1,2 Doping with indium, gallium, or aluminum improves these properties.3-5 These characteristicsMolecular Orbital Studies of Zinc Oxide Chemical Vapor Deposition: Gas-Phase Hydrolysis of Diethyl deposition of zinc oxide thin films can be carried out with diethyl zinc and water vapor. The present study

Schlegel, H. Bernhard

87

Analysis of the growth modes for gallium arsenide metalorganic vapor-phase epitaxy  

E-print Network

Analysis of the growth modes for gallium arsenide metalorganic vapor-phase epitaxy D. C. Law March 2000 The surface roughness of gallium arsenide 001 films produced by metalorganic vapor for gallium surface diffusion has been estimated: Ed 1.35 0.1 eV. © 2000 American Institute of Physics. S0021

Li, Lian

88

VAPOR-PHASE DECONTAMINATION OF APPLES CONTAINING ESCHERICHIA COLI  

Technology Transfer Automated Retrieval System (TEKTRAN)

Improved methods of decontaminating apples containing human pathogens are required. In this investigation, application of gaseous antimicrobial agents was investigated. An apparatus, which transfers vapor from hot antimicrobial solutions to a treatment vessel, was evaluated with Golden Delicious app...

89

Vapor-phase preparation of gold nanocrystals by chloroauric acid pyrolysis.  

PubMed

We report that gold nanocrystals can be prepared from vapor phase using chloroauric acid (HAuCl4) as the precursor. By tuning the vapor-phase deposition parameters, the size and space distribution of the gold nanocrystals can be well controlled on substrates. Systematic control experiments demonstrate that intermediate AuCl and AuCl3 products pyrolyzed from HAuCl4 play an essential role in this vapor-phase deposition process. Compared to conventional wet-chemical synthesis process, vapor-phase process enables direct deposition of gold nanoparticles on solid substrates with better coverage and uniformity, which may find applications in surface-enhanced Raman scattering and plasmon-enhanced photocatalysis. PMID:25463171

Chen, Yiqin; Tian, Xuezeng; Zeng, Wei; Zhu, Xupeng; Hu, Hailong; Duan, Huigao

2015-02-01

90

Smoke composition and predicting relationships for international commercial cigarettes smoked with three machine-smoking conditions.  

PubMed

The study objectives were to determine the effects of smoking machine puffing parameters on mainstream smoke composition and to express those effects as predicting relationships. Forty-eight commercial Philip Morris USA and Philip Morris International cigarettes from international markets and the 1R4F reference cigarette were machine-smoked using smoking conditions defined by the International Organization of Standardization (ISO), the Massachusetts Department of Public Health (MDPH), and Health Canada (HC). Cigarette tobacco fillers were analyzed for nitrate, nicotine, tobacco-specific nitrosamines (TSNA), and ammonia. Mainstream yields for tar and 44 individual smoke constituents and "smoke pH" were determined. Cigarette constituent yields typically increased in the order ISOcigarettes with higher initial filter ventilation and were also generally greater for vapor-phase constituents than for particulate-phase constituents. Predicting relationships were developed between ISO tar and ISO, MDPH, and HC constituent yields and between MDPH tar and HC tar and respective smoking condition yields. MDPH and HC constituent yields could be predicted with similar reliability using ISO tar or the corresponding smoking-condition tar. The reliability of the relationships varied from strong to weak, depending on particular constituents. Weak predicting relationships for nitrogen oxides and TSNA's, for example, were improved with inclusion of tobacco filler composition factors. "Smoke pH" was similar for all cigarettes at any one smoking condition, and overall marginally lower at HC conditions than at ISO or MDPH conditions. PMID:15748796

Counts, M E; Morton, M J; Laffoon, S W; Cox, R H; Lipowicz, P J

2005-04-01

91

Selective Area Metal–Organic Vapor Phase Epitaxy of Nitride Semiconductors for Multicolor Emission  

Microsoft Academic Search

Selective area metal-organic vapor phase epitaxy (SA-MOVPE) allows in-plane control of emission wavelength by tailored width of masks. For InGaN\\/GaN multiple quantum wells (MQWs), modulation of luminescence wavelength was achieved based on a balance between vapor-phase diffusion of group-III precursors and their surface incorporation. For the basic understanding of the SA-MOVPE of nitride semiconductors, thickness profiles of GaN, InN, AlN,

Tomonari Shioda; Yuki Tomita; Masakazu Sugiyama; Yukihiro Shimogaki; Yoshiaki Nakano

2009-01-01

92

Tribology Letters Vol. 10, No. 3, 2001 179 Activation of the SiC surface for vapor phase lubrication  

E-print Network

of non-liquid lubrica- tion systems such as vapor phase lubrication (VPL), solid powder lubricants lubrication by Fe chemical vapor deposition from Fe(CO)5 Daxing Ren, Dougyong Sung and Andrew J. Gellman to the vapor phase lubrication of ceramics using organophosphorus compounds. The surface of SiC is shown

Gellman, Andrew J.

93

VAPOR-CONDENSED PHASE PROCESSES IN THE EARLY SOLAR SYSTEM. L. Grossman. Department of the  

E-print Network

VAPOR-CONDENSED PHASE PROCESSES IN THE EARLY SOLAR SYSTEM. L. Grossman. Department@uchicago.edu. Equilibrium thermodynamic calculations of the sequence of condensation of phases from a cooling gas of solar that they underwent melting after condensation, crystallizing into the same phase as- semblage as their precursors

Grossman, Lawrence

94

Generalization of data on the permittivity of the liquid and vapor phases of water for determining the vapor content of two-phase states  

NASA Astrophysics Data System (ADS)

Experimental data on the permittivity of water and steam depending on the ratio of the density to temperature have been generalized. The relations obtained allow one to calculate the vapor content of two-phase states in application to thermal-power plants.

Mulev, Yu. V.; Arefiev, K. M.; Belyaeva, O. V.; Mulev, M. Yu.; Zayats, T. A.

2011-09-01

95

REDOX AND ELECTROPHILIC PROPERTIES OF VAPOR- AND PARTICLE-PHASE COMPONENTS OF AMBIENT AEROSOLS  

PubMed Central

Particulate matter (PM) has been the primary focus of studies aiming to understand the relationship between the chemical properties of ambient aerosols and adverse health effects. Size and chemical composition of PM have been linked to their oxidative capacity which has been postulated to promote or exacerbate pulmonary and cardiovascular diseases. But in the last few years, new studies have suggested that volatile and semivolatile components may also contribute to many adverse health effects. The objectives of this study were: i) assess for the first time the redox and electrophilic potential of vapor-phase components of ambient aerosols, and ii) evaluate the relative contributions of particle- and vapor-fractions to the hazard of a given aerosol. To achieve these objectives vapor- and particle-phase samples collected in Riverside (CA) were subjected to three chemical assays to determine their redox and electrophilic capacities. The results indicate that redox active components are mainly associated with the particle-phase, while electrophilic compounds are found primarily in the vapor-phase. Vapor-phase organic extracts were also capable of inducing the stress responding protein, heme-oxygenase-1 (HO-1), in RAW264.7 murine macrophages. These results demonstrate the importance of volatile components in the overall oxidative and electrophilic capacity of aerosols, and point out the need for inclusion of vapors in future health and risk assessment studies. PMID:20152964

Eiguren-Fernandez, Arantzazu; Shinyashiki, Masaru; Schmitz, Debra A.; DiStefano, Emma; Hinds, William; Kumagai, Yoshito; Cho, Arthur K.; Froines, John R.

2010-01-01

96

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

97

Strawboard from vapor phase acetylation of wheat straw  

Microsoft Academic Search

Commercial ground wheat straw was used in a central composite response surface experimental design to examine four acetylating process variables: reaction temperature, reaction time, initial moisture content of straw, and the vapor flow rate of chemical reagent. The response variable was acetyl content determined as a function of straw weight gain. Diphenylmethyane diisocyante was used as a binder to prepare

Greggory S Karr; Xiuzhi S Sun

2000-01-01

98

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...

99

Vapor Phase Detection Using Chemi-Resistor Sensor Arrays  

SciTech Connect

This paper focuses on two main areas: understanding sensor response times so as to obtain improved time response in the field when needed for vapor tracking and classification, and improved theoretical understanding of the sensor response properties that generate the pattern on the array in response to a given analyte.

Nathan S. Lewis

1999-02-17

100

Vapor-Phase Stoichiometry and Heat Treatment of CdTe Starting Material for Physical Vapor Transport  

NASA Technical Reports Server (NTRS)

Six batches of CdTe, having total amounts of material from 99 to 203 g and gross mole fraction of Te, X(sub Te), 0.499954-0.500138, were synthesized from pure Cd and Te elements. The vapor-phase stoichiometry of the assynthesized CdTe batches was determined from the partial pressure of Te2, P(sub Te2) using an optical absorption technique. The measured vapor compositions at 870 C were Te-rich for all of the batches with partial pressure ratios of Cd to Te2, P(sub Cd)/P(sub Te2), ranging from 0.00742 to 1.92. After the heat treatment of baking under dynamic vacuum at 870 C for 8 min, the vapor-phase compositions moved toward that of the congruent sublimation, i.e. P(sub Cd)/P(sub Te2) = 2.0, with the measured P(sub Cd)/P(sub Te2) varying from 1.84 to 3.47. The partial pressure measurements on one of the heat-treated samples also showed that the sample remained close to the congruent sublimation condition over the temperature range 800-880 C.

Su, Ching-Hua; Sha, Yi-Gao; Lehoczky, S. L.; Liu, Hao-Chieh; Fang, Rei; Brebrick, R. F.

1998-01-01

101

Concurrent Growth of Kirkendall Pores and Vapor-Solid-Solid Protuberances on Ni Wires During Mo Vapor-Phase Deposition  

NASA Astrophysics Data System (ADS)

During vapor-phase deposition at 1273 K (1000 °C), by pack cementation, of Mo onto 127- ?m-diameter Ni wires, two phenomena are observed to occur concurrently, leading to strong surface roughening: (i) the inward radial growth of Kirkendall pores below the wire surface and (ii) the outward growth from the wire surface of protuberances with sizes as large as 15 ?m. High-aspect-ratio Kirkendall pores as long as 21 ?m are created because of imbalanced interdiffusion between Mo and Ni. These pores in turn, by reducing the flow of Mo into the wires, may enhance the outward growth of Mo-rich protuberances, further roughening the wire surface. These protuberances have faceted tips as well as terraces and steps, indicating that their growth is governed by the vapor-solid-solid mechanism.

Wang, Cong; Dunand, David C.

2014-12-01

102

Concurrent Growth of Kirkendall Pores and Vapor-Solid-Solid Protuberances on Ni Wires During Mo Vapor-Phase Deposition  

NASA Astrophysics Data System (ADS)

During vapor-phase deposition at 1273 K (1000 °C), by pack cementation, of Mo onto 127-?m-diameter Ni wires, two phenomena are observed to occur concurrently, leading to strong surface roughening: (i) the inward radial growth of Kirkendall pores below the wire surface and (ii) the outward growth from the wire surface of protuberances with sizes as large as 15 ?m. High-aspect-ratio Kirkendall pores as long as 21 ?m are created because of imbalanced interdiffusion between Mo and Ni. These pores in turn, by reducing the flow of Mo into the wires, may enhance the outward growth of Mo-rich protuberances, further roughening the wire surface. These protuberances have faceted tips as well as terraces and steps, indicating that their growth is governed by the vapor-solid-solid mechanism.

Wang, Cong; Dunand, David C.

2014-09-01

103

Toxicological assessment of kretek cigarettes Part 6: The impact of ingredients added to kretek cigarettes on smoke chemistry and in vitro toxicity.  

PubMed

Mainstream smoke (MS) from experimental kretek cigarettes with three ingredient mixes at low (typical use level) and high (2.5 or 3 times that level) inclusion rates was compared to a control kretek cigarette of identical construction (cloves and humectants), but without the addition of ingredients. 350 ingredients, commonly used in various combinations and in a limited number in a given brand in the manufacture of marketed kretek cigarettes were assessed. The MS composition of the kretek cigarettes was characterized by a comprehensive set of analytes (55 smoke constituents). Furthermore, the smoke was assessed in vitro for its cytotoxicity in the Neutral Red Uptake assay (particle phase and gas/vapor phase separately) in mouse embryo BALB/c 3T3 cells, and for mutagenicity/genotoxicity in the Salmonella typhimurium reverse mutation assay and the mammalian cell mouse lymphoma TK assay in L5178Y cells, the latter with and without metabolic activation. There were some statistically significant differences in the yield of smoke constituents (increases as well as decreases, nearly all of them less than ±20%) as a result of the addition of the ingredient mixes. However, the addition of the three different mixes of ingredients to the experimental kreteks did not change the in vitro cytotoxicity and mutagenicity/genotoxicity of the smoke, when compared to the control kretek cigarette. PMID:25496764

Roemer, E; Dempsey, R; Hirter, J; Deger Evans, A; Weber, S; Ode, A; Wittke, S; Schorp, M K

2014-12-01

104

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

105

Cigarette Money  

Microsoft Academic Search

We study how commodities emerge as money, the way cigarettes did in POW camps. We characterize how specialization, trading frictions, intrinsic properties of goods, and the amount of fiat money determine whether a commodity serves as money and its value. In some equilibria, the exchange value of commodity money is pinned down by its consumption value; in others, it is

Kenneth Burdett; Alberto Trejos; Randall Wright

2001-01-01

106

Liquid phase epitaxy of GaP by a temperature difference method under controlled vapor pressure  

Microsoft Academic Search

A series of experiments have been done in which the properties of GaP grown by liquid phase epitaxy (LPE) have been varied by providing an additional source of phosphorus via the vapor phase. The quality of the crystals, as judged from gross defect features observed in etched cross sections, is a function of the amount of phosphorus added to the

J. Nishizawa; Y. Okuno

1975-01-01

107

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

108

Vapor-Phase Lubricants: Nanometer-scale Lubrication Mechanisms and Uptake on Silicon  

NASA Astrophysics Data System (ADS)

The concept of lubricating high temperature bearing surfaces with organic vapors which react with a surface to form a solid lubricating film has existed for at least forty years, with substantial efforts beginning in the 1980's and continuing to the present day. While vapor-phase lubricants have primarily been studied within the context of macroscopic system performance, they may well prove to be of critical importance to tribological performance in sub-micron mechanical systems as well. This is because the vapor phase may ultimately prove to be the most effective, if not only, means to deliver and/or replenish a lubricant that can withstand a variety of extreme environmental conditions that a MEMS device is likely to encounter. In order to investigate the viability of vapor-phase lubrication for MEMS applications, we have studied molecular scale tribological properties and gas uptake rates for four known organophosphate lubricants in controlled environments on silicon and gold substrates. The first study involves Quartz Crystal Microweighing investigations of the uptake rates of lubricant vapors from the vapor phase in vacuum conditions. With the intent of modelling actual MEMS contacts, we have also constructed a simple nanomechanical system consisting of a Scanning Tunneling Microscope tip dragging on the surface of a Quartz Crystal Microbalance electrode. This system allows us to monitor lubricant performance in realistic sliding conditions of up to 2 m/s. Finally, work is in progress to study the effect of these vapor-phase lubricants on actual MEMS devices with contacting silicon surfaces. Work supported by NSF and AFOSR.

Neeyakorn, Worakarn; Varma, Manju; Jaye, Cherno; Hook, Adam; Krim, Jacqueline

2004-03-01

109

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

110

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

111

Bottom-up nanofabrication through catalyzed vapor phase HF etching of SiO2  

NASA Astrophysics Data System (ADS)

We show that a wide range of inorganic and organic molecules or nanostructures can enhance the vapor phase HF etching of SiO2 resulting in a negative tone pattern transfer to a SiO2 substrate. The templates used in this study include micron- and nanometer-sized NaCl crystals, graphene oxide flakes, and albumin molecules. In all cases, a negative-tone pattern transfer to the underlying SiO2 substrate was obtained. The results suggest that vapor phase HF etching could be a general purpose pattern transfer technique for nanoscale and supramolecular templates.

Zhao, Shichao; Liu, Haitao

2015-01-01

112

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

113

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...

114

Vapor-condensed phase processes in the early solar system Lawrence GROSSMAN*  

E-print Network

Vapor-condensed phase processes in the early solar system Lawrence GROSSMAN* Department accepted 26 September 2009) Abstract­Equilibrium thermodynamic calculations of the sequence of condensation of condensation, and some may be pristine condensates that escaped later melting. Compact Type A and Type B

Grossman, Lawrence

115

Vapor-Phase Deposition of Monofunctional Alkoxysilanes for Sub-Nanometer-Level Biointerfacing  

E-print Network

-compatible processes.[19,20] In these vapor-phase processes, the precursor chemistry is easily controlled and efficient-Champaign Urbana, IL 61801 (USA) Prof. S. E. Clare Indiana University School of Medicine Indianapolis, IN 46202 (USA) Prof. D. E. Bergstrom Department of Medicinal Chemistry and Molecular Pharmacology Birck

Cunningham, Brian

116

DEVELOPMENT OF AN AIR-TO-LEAF VAPOR PHASE TRANSFER FACTOR FOR DIOXINS AND FURANS  

EPA Science Inventory

Results of an experiment in which grass was grown in a greenhouse and outdoors, and in soils of different concentration levels of dioxins and furans, were used in a modeling exercise to derive an air-to-leaf vapor phase transfer factor. The purpose of the experiment was to under...

117

Simplified thermodynamic functions for vapor-liquid phase separation and fountain effect pumps  

NASA Technical Reports Server (NTRS)

He-4 fluid handling devices near 2 K require novel components for non-Newtonian fluid transport in He II. Related sizing of devices has to be based on appropriate thermophysical property functions. The present paper presents simplified equilibrium state functions for porous media components which serve as vapor-liquid phase separators and fountain effect pumps.

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

1984-01-01

118

Underwater vapor phase burning of aluminum particles and on aluminum ignition during steam explosions  

Microsoft Academic Search

Recently reported experimental studies on aluminum-water steam explosions indicate that there may be a critical metal temperature at which the process changes over from a physical explosion to one which is very violent and involves the rapid liberation of chemical energy. In this report we examine the hypothesis that vapor-phase burning of aluminum is a necessary condition for the occurrence

Epstein

1991-01-01

119

POTENTIAL USE AND MODIFICATION OF EXISTING MESOCOSMS FOR VAPOR PHASE PHOTOTOXICITY  

EPA Science Inventory

With vapor phase plant toxicity testing becoming a requirement in Europe, there is a pressing need to develop and implement acceptable tests protocols. The quickest way to proceed is to examine and modify existing methodologies while determining if new technologies are needed. ...

120

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

121

Retronasal Discrimination Between Vapor-Phase Long-Chain, Aliphatic Fatty Acids  

E-print Network

2006; Warner et al. 1997). Linoleic acid is "the major constituent of many vegetables oils, including important (see Simopoulos 2008). Linoleic and oleic acids are the dominant fatty acids in vegetable oils vegetable oils (Gunstone 2002). During consumption of foods and beverages, vapor- phase components

122

ORIGINAL PAPER Dynamics of Vapor-phase Organophosphates on Silicon and OTS  

E-print Network

ORIGINAL PAPER Dynamics of Vapor-phase Organophosphates on Silicon and OTS Worakarn Neeyakorn � of the uptake and nanotribology of organophosphate (tricresylphosphate (TCP) and t-butyl phenyl phosphate (TBPP applications. About 3­5 monolayer-thick organophosphate films are observed to form readily on both silicon

Krim, Jacqueline

123

EFFECT OF DIRECTIONAL SWITCHING FREQUENCY ON TOLUENE DEGRADATION IN A VAPOR-PHASE BIOREACTOR. (R826168)  

EPA Science Inventory

A potential method to improve biomass distribution and the stability of vapor-phase bioreactors is to operate them in a directionally switching mode such that the contaminant air stream direction is periodically reversed through the reactor. In this study, the effect of switching...

124

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

125

Effect of vapor-phase mass transfer on aquifer restoration  

SciTech Connect

Volatile organic chemicals (VOC) are a frequent source of groundwater contamination in North Carolina and throughout the United States and other developed countries. The work is considered a subset of the general multiphase flow and transport problem: fluid flow and contaminant transport in the gas phase of the unsaturated zone. The specific purpose of the work was to investigate gas-phase (VOC) transport phenomena at the field scale to assess the relative importance of operative transport phenomena. A field research site was established at an active fire training area on Pope Air Force Base. Monitoring of groundwater flow and gas-phase contaminant distributions was accomplished as a function of three spatial dimensions and time. These distributions are reported and interpreted with respect to the current level of understanding of gas-phase transport phenomena. Consideration is given to advective transport, diffusive transport, interphase mass transfer, and multicomponent effects. Numerical modeling is used to evaluate expected steady-state contaminant distributions in the unsaturated zone and to assess relative time scales of operative transport processes. Reasonable agreement is achieved between model simulations and observed concentration distributions in the field, with a dominant vertical transport component shown in both predicted and observed contaminant distributions.

Miller, C.T.; Staes, E.G.

1992-02-01

126

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

127

Space cryogenics components based on the thermomechanical effect - Vapor-liquid phase separation  

NASA Technical Reports Server (NTRS)

Applications of the thermomechanical effect has been qualified including incorporation in large-scale space systems in the area of vapor-liquid phase separation (VLPS). The theory of the porous-plug phase separator is developed for the limit of a high thermal impedance of the solid-state grains. Extensions of the theory of nonlinear turbulent flow are presented based on experimental results.

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

1989-01-01

128

HeII co-current two phase flow at high vapor velocities  

Microsoft Academic Search

In the framework of LHC studies, we have performed several experiments on HeII co-current two-phase flow. It was found that for high vapor velocities, the heat exchange capacity between the HeII flow and the pipe wall is significantly better than what can be accounted for by the liquid to wall interface of a stratified two-phase flow pattern. This seems to

B. Rousset; B. Jager; E. di Muoio; L. Puech; P. Thibault; R. Vallcorba; R. van Weelderen; P. E. Wolf

2002-01-01

129

Study Suggests Link Between E-Cigarettes, Respiratory Infections  

MedlinePLUS

... the investigators found. In follow-up testing, lab mice exposed to e-cigarette vapor also appeared more ... with a cold from rhinovirus, compared with unexposed mice. The American Vaping Association, an industry group representing ...

130

Custom Mentholation of Commercial Cigarettes for Research Purposes  

PubMed Central

In the U.S. menthol remains the sole permitted characterizing cigarette flavor additive in part because efforts to link menthol cigarette use to increased tobacco-related disease risk have been inconclusive. To perform definitive studies, cigarettes that differ only in menthol content are required, yet these are not commercially available. We prepared research cigarettes differing only in menthol content by deposition of L-menthol vapor directly onto commercial nonmenthol cigarettes, and developed a method to measure a cigarette’s menthol and nicotine content. With our custom-mentholation technique we achieved the desired moderately high menthol content (as compared to commercial brands) of 6.7 ± 1.0 mg/g (n = 25) without perturbing the cigarettes’ nicotine content (17.7 ± 0.7 mg/g [n = 25]). We also characterized other pertinent attributes of our custom-mentholated cigarettes, including percent transmission of menthol and nicotine to mainstream smoke and the rate of loss of menthol over time during storage at room temperature. We are currently using this simple mentholation technique to investigate the differences in human exposure to selected chemicals in cigarette smoke due only to the presence of the added menthol. Our cigarettes will also aid in the elucidation of the effects of menthol on the toxicity of tobacco smoke.

MacGregor, Ian C.; Stanfill, Stephen B.; Gordon, Sydney M.; Turner, Douglas J.; Butler, Jenny M.; Hanft, Elizabeth A.; Kim, Hyoshin; Kroeger, Robyn R.; Brinkman, Marielle C.; Tefft, Margaret E.; Clark, Pamela I.; Buehler, Stephanie S.

2014-01-01

131

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

132

Electronic cigarettes: the road ahead.  

PubMed

Electronic cigarettes (e-cig) are proliferating in the world's lucrative nicotine delivery market at an alarmingly fast pace. E-cig are aggressively marketed as an alternative to conventional tobacco cigarettes, although very little is known about the health consequences of e-cig use. Chemical analysis of e-cig vapor/liquid has shown that many toxicants and carcinogens present in cigarette smoke are also found, albeit generally in lower concentrations, in a wide range of e-cig products. Notwithstanding the presence of toxicants and carcinogens in e-cig products, the biological effects of exposure to these contaminants have not been determined in e-cig users. The ongoing research and future investigations on e-cig initiation, use, perceptions, dependence, and toxicity are expected to provide empirical evidence that can be used to inform the general public, scientific community, and regulatory authorities of the health risks/benefits associated with e-cig use. This information will help stimulate scientists in the field of tobacco research, as well as assist the regulatory agencies in making scientifically based decisions on the development and evaluation of regulations on tobacco products to protect the public's health. Finding the scientific underpinnings for the health risks/benefits of e-cig use can impact millions of people who are increasingly turning to e-cig as a replacement for or complement to conventional tobacco cigarettes. PMID:24952095

Besaratinia, Ahmad; Tommasi, Stella

2014-09-01

133

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

134

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

135

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

136

Organic solvent vapor effects on phase transition of ? and ? tegafur upon grinding with solvent additives.  

PubMed

Solvent effects on ? tegafur (5-fluoro-1-(tetrahydro-2-furyl)uracil) phase transition to ? tegafur during grinding with solvent additive, as well as phase transition in samples exposed to 95% relative solvent vapor pressure has been studied in this research. Samples containing 0.5% and 0.1% of ? tegafur in ? and ? tegafur mixture, as well as samples of pure ? tegafur were ground with different solvent additives, and conversion degrees depending on the solvent were determined using PXRD method. Samples with ? and ? tegafur weight fraction of 1:1 were exposed to 95% relative solvent vapor pressure, and phase transition rates were determined. Solubility of ? tegafur, solvent sorption and desorption behavior on ? and ? tegafur have been examined. It was found that the conversion degree of ? tegafur to ? tegafur mainly depends on solubility of ? tegafur in the relevant solvent, and the conversion degree to ? tegafur is higher in such solvents, where solubility of ? tegafur is higher. The samples ground in a ball mill with solvent additive had a trend of phase transition dynamics from ? tegafur to ? tegafur similar to the samples exposed to 95% relative solvent vapor pressure. PMID:23318369

Bobrovs, Raitis; Save?jeva, Olga; Kapace, Agnese; Plauka, Zane; Acti?š, Andris

2013-02-25

137

Electronic cigarettes: a review of safety and clinical issues.  

PubMed

This clinical case conference discusses 3 cases of patients using electronic cigarettes. Electronic cigarettes, also referred to as electronic nicotine delivery systems or "e-cigarettes," generally consist of a power source (usually a battery) and a heating element (commonly referred to as an atomizer) that vaporize a solution (e-liquid). The user inhales the resulting vapor. E-liquids contain humectants such as propylene glycol and/or vegetable glycerin, flavorings, and usually, but not always, nicotine. Each patient's information is an amalgamation of actual patients and is presented and then followed by a discussion of clinical issues. PMID:25089953

Weaver, Michael; Breland, Alison; Spindle, Tory; Eissenberg, Thomas

2014-01-01

138

Vapor Compression Hybrid Two-Phase Loop Technology for Lunar Surface Applications  

NASA Astrophysics Data System (ADS)

NASA's vision for Space Exploration that would return humans to the Moon by 2020 in preparation for human explorations of Mars. This requires innovative technical advances. The lunar mission requires a temperature-lift (heat pump) technology to reject waste heat to hot lunar surface (heat sink) environments during lunar daytime. The lunar outpost and Lunar Surface Access Module (LSAM) to operate anywhere during the hot lunar daytime require a high performance and energy-efficient, yet reliable refrigeration technology. A vapor compressor-driven hybrid two-phase loop was developed for such high temperature-lift applications. The vapor compression loop used an advanced porous wick evaporator capable of gravity-insensitive capillary phase separation and excess liquid management to achieve high temperature-lift, large-area, isothermal and high heat flux cooling capability and efficient compression. The high temperature lift will allow the lunar surface systems use compact radiators by increased heat rejection temperature.

Park, Chanwoo; Sunada, Eric

2008-01-01

139

Exciton-exciton scattering in vapor phase ZnO nanoparticles  

NASA Astrophysics Data System (ADS)

Photoluminescence (PL) properties of suspended ZnO nanoparticles formed in vapor phase due to the condensation of the Nd:YAG laser ablated ZnO plasma species are investigated by varying both ablating and excitation intensity at different time delays with respect to the ablating pulse and at different axial distances from the target surface. Emission due to inelastic exciton-exciton (X-X) scattering is observed and is found to be dependent on the size of the vapor phase ZnO nanoparticles. The PL intensity shows nonlinear behavior with increasing ablating intensity, indicating generation and participation of more excitons in X-X scattering process in lager size ZnO nanoparticles.

Mohanta, Antaryami; Kung, Patrick; Thareja, Raj K.

2015-01-01

140

In situ, subsurface monitoring of vapor-phase TCE using fiber optics  

SciTech Connect

A vapor-phase, reagent-based, fiber optic trichloroethylene (TCE) sensor developed by Lawrence Livermore National Laboratory (LLNL) was demonstrated at the Savannah River Site (SRS) in two configurations. The first incorporated the sensor into a down-well instrument bounded by two inflatable packers capable of sealing an area for discrete depth analysis. The second involved an integration of the sensor into the probe tip of the Army Corps of Engineers Waterways Experiment Station (WES) cone penetrometry system. Discrete depth measurements of vapor-phase concentrations of TCE in the vadose zone were successfully made using both configurations. These measurements demonstrate the first successful in situ sensing (as opposed to sampling) of TCE at a field site.

Rossabi, J. [Westinghouse Savannah River Co., Aiken, SC (United States); Colston, B. Jr.; Brown, S.; Milanovich, F. [Lawrence Livermore National Lab., CA (United States); Lee, L.T. Jr. [Army Engineer Waterways Experiment Station, Vicksburg, MS (United States). Geotechnical Lab.

1993-03-05

141

Transport studies on very high purity gallium arsenide grown by organometallic vapor phase epitaxy  

Microsoft Academic Search

Very high purity GaAs layers have been grown in a modified organometallic vapor phase epitaxy (OMVPE) system using trimethyl gallium (TMGa) and arsine including the purest layer ever reported from these chemical sources with purity approaching the very best reported by the chloride-VPE technique. Several of these high purity GaAs samples were chemically etched into Kelvin and Greek cross structures

Cheung Fat Tsang

1997-01-01

142

Sintered plug flow modulation of a vapor-liquid phase separator for a helium II vessel  

NASA Technical Reports Server (NTRS)

Presented is a system for modulation of a superfluid (helium II) flow in a vapor-liquid phase separator, for use in cryogenic storage tanks in future space missions. The system consists of a semicircular mechanically operated shutter, downstream of the separator plug, rotated at 0.1 rpm to control the operational surface area of the separator. The mass flow rate was varied from 10 to 22 mg/s. Pressure gradients across the plug are also discussed.

Frederking, T. H. K.; Chuang, C.; Kamioka, Y.; Lee, J. M.; Yuan, S. W. K.

1984-01-01

143

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

144

Effect of thermodiffusion on perfection of crystal structures formed by condensation from vapor phase  

Microsoft Academic Search

Results are reported of an investigation of the effect of nonuniform synthesis conditions stimulating thermodiffusion on the\\u000a perfection of the crystalline structure of cadmium telluride films synthesized in vacuum by condensation from the vapor phase.\\u000a Results of technological, geometrical, electorgraphical, and electron-microscopic studies are given. It is shown that the\\u000a positive effect of the nonuniform conditions on the perfection of

A. P. Belyaev; V. P. Rubets; M. Yu. Nuzhdin; I. P. Kalinkin

2002-01-01

145

Temperature dependence of Raman scattering of ZnSe nanoparticle grown through vapor phase  

Microsoft Academic Search

ZnSe nanoparticles were synthesized through a vapor-phase reaction of zinc and selenium and deposited as random aggregates on a water-cooled copper collector. X-ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrate that the as-grown nanoparticles are polycrystalline ZnSe nanoparticles. Their diameters can be controlled through the deposition temperature. Raman spectra of nanoparticles with different diameter-size distribution and bulk material were

Guowei Lu; Huizi An; Yu Chen; Jiehui Huang; Hongzhou Zhang; Bin Xiang; Qing Zhao; Dapeng Yu; Weimin Du

2005-01-01

146

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

147

Influence of aluminum on doping of ytterbium in optical fiber synthesized by vapor phase technique  

NASA Astrophysics Data System (ADS)

The process conditions of vapor phase doping technique for fabricating rare earth (RE) doped optical fiber have been systematically investigated to achieve better control over RE incorporation. Experimental results showed that the amount of RE incorporation can be precisely controlled by adjusting Al ion concentration in the inlet gas mixture. The extent of RE incorporation can also be predicted for any composition of inlet gas mixture if all other process parameters remain constant. The investigation helps to obtain the optimum conditions necessary to produce fibers of given specification and thus achieve greater reproducibility. For the first time co-operative phenomenon has been established through gas phase technique.

Saha, Maitreyee; Pal, Atasi; Pal, Mrinmay; Sen, Ranjan

2015-01-01

148

Chemically sensitive polymer-mediated nanoporous alumina SAW sensors for the detection of vapor-phase analytes  

E-print Network

) of polydimethylsiloxane (PDMS) were developed to simultaneously provide selective sorption and permeation characteristics towards vapor-phase analytes. The porous nature of the underlying alumina coating provides for this real-time evaluation of sorption and permeation...

Perez, Gregory Paul

2005-08-29

149

Biodegradation of high concentrations of benzene vapors in a two phase partition stirred tank bioreactor  

PubMed Central

The present study examined the biodegradation rate of benzene vapors in a two phase stirred tank bioreactor by a bacterial consortium obtained from wastewater of an oil industry refinery house. Initially, the ability of the microbial consortium for degrading benzene was evaluated before running the bioreactor. The gaseous samples from inlet and outlet of bioreactor were directly injected into a gas chromatograph to determine benzene concentrations. Carbone oxide concentration at the inlet and outlet of bioreactor were also measured with a CO2 meter to determine the mineralization rate of benzene. Influence of the second non-aqueous phase (silicon oil) has been emphasized, so at the first stage the removal efficiency (RE) and elimination capacity (EC) of benzene vapors were evaluated without any organic phase and in the second stage, 10% of silicon oil was added to bioreactor media as an organic phase. Addition of silicon oil increased the biodegradation performance up to an inlet loading of 5580?mg/m3, a condition at which, the elimination capacity and removal efficiency were 181?g/m3/h and 95% respectively. The elimination rate of benzene increased by 38% in the presence of 10% of silicone oil. The finding of this study demonstrated that two phase partition bioreactors (TPPBs) are potentially effective tools for the treatment of gas streams contaminated with high concentrations of poorly water soluble organic contaminant, such as benzene. PMID:23369269

2013-01-01

150

The mechanism of vapor phase hydration of calcium oxide: implications for CO2 capture.  

PubMed

Lime-based sorbents are used for fuel- and flue-gas capture, thereby representing an economic and effective way to reduce CO2 emissions. Their use involves cyclic carbonation/calcination which results in a significant conversion reduction with increasing number of cycles. To reactivate spent CaO, vapor phase hydration is typically performed. However, little is known about the ultimate mechanism of such a hydration process. Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic process, which progresses via an intermediate disordered phase prior to the final formation of oriented Ca(OH)2 nanocrystals. The strong structural control during this solid-state phase transition implies that the microstructural features of the CaO parent phase predetermine the final structural and physicochemical (reactivity and attrition) features of the product hydroxide. The higher molar volume of the product can create an impervious shell around unreacted CaO, thereby limiting the efficiency of the reactivation process. However, in the case of compact, sintered CaO structures, volume expansion cannot be accommodated in the reduced pore volume, and stress generation leads to pervasive cracking. This favors complete hydration but also detrimental attrition. Implications of these results in carbon capture and storage (CCS) are discussed. PMID:25233236

Kud?acz, Krzysztof; Rodriguez-Navarro, Carlos

2014-10-21

151

E-Cigarettes  

MedlinePLUS

... nicotine — a highly addictive drug — into the body. Electronic cigarettes are battery-powered smoking devices often designed to ... an unhealthy dose of nicotine and other chemicals. Electronic cigarettes started out being marketed to smokers as a ...

152

E-Cigarettes  

MedlinePLUS

... nicotine — a highly addictive drug — into your body. Electronic cigarettes are battery-powered smoking devices often designed to ... an unhealthy dose of nicotine and other chemicals. Electronic cigarettes started out being marketed to smokers as a ...

153

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

154

Vapor-Phase Free Radical Polymerization in the Presence of Ionic Liquids  

NASA Astrophysics Data System (ADS)

Ionic liquids (ILs) have recently attracted significant interest as an environmentally-friendly alternative to traditional volatile organic solvents because ILs are non-volatile, non-flammable, and can be easily recycled. ILs can be exploited in many ways to improve the selectivity and kinetics of chemical reactions, including polymer synthesis. Ionic liquids have negligible vapor pressure and are therefore stable under vacuum. A few studies have investigated ILs as substrates in inorganic vacuum deposition processes, but to our knowledge ILs have not been used in vapor phase polymerization systems. We have recently introduced ionic liquids into the initiated chemical vapor deposition (iCVD) process for the first time. The iCVD polymerization process occurs via a free-radical mechanism, and the deposited polymeric films are compositionally analogous to solution-phase polymers. Despite the wide range of polymers that have been synthesized using iCVD, it has proven difficult to polymerize monomers with low surface concentrations such as styrene and low propagation rates such as methyl methacrylate and it is difficult to produce block copolymers. In this talk, we will show that our novel ILiCVD system can address some of these shortcomings. We will explain the effects of deposition time, temperature, and monomer solubility on the morphology of the polymer and the molecular weight of the polymer chains.

Gupta, Malancha

2011-03-01

155

Design and optimization of a total vaporization technique coupled to solid-phase microextraction.  

PubMed

Solid-phase microextraction (SPME) is a popular sampling technique in which chemical compounds are collected with a sorbent-coated fiber and then desorbed into an analytical instrument such as a liquid or gas chromatograph. Typically, this technique is used to sample the headspace above a solid or liquid sample (headspace SPME), or to directly sample a liquid (immersion SPME). However, this work demonstrates an alternative approach where the sample is totally vaporized (total vaporization SPME or TV-SPME) so that analytes partition directly between the vapor phase and the SPME fiber. The implementation of this technique is demonstrated with polydimethylsiloxane-divinylbenzene (PDMS-DVB) and polyacrylate (PA) coated SPME fibers for the collection of nicotine and its metabolite cotinine in chloroform extracts. The most important method parameters were optimized using a central composite design, and this resulted in an optimal extraction temperature (96 °C), extraction time (60 min), and sample volume (120 ?L). In this application, large sample volumes up to 210 ?L were analyzed using a volatile solvent such as chloroform at elevated temperatures. The sensitivity of TV-SPME is nearly twice that of liquid injection for cotinine and nearly 6 times higher for nicotine. In addition, increased sampling selectivity of TV-SPME permits detection of both nicotine and cotinine in hair as biomarkers of tobacco use where in the past the detection of cotinine has not been achieved by conventional SPME. PMID:25313649

Rainey, Christina L; Bors, Dana E; Goodpaster, John V

2014-11-18

156

Cross-correlation video recording of gas-vapor-droplet two-phase flows  

NASA Astrophysics Data System (ADS)

The experimental investigations of gas-vapor-droplet two-phase flow formation during single water droplets and their aggregate motion through high-temperature (more than 1000 K) combustion products have been conducted with usage of cross-correlation measuring facility and optical methods of "tracer" visualization ("Particle Image Velocimetry" and "Interferometric Particle Imaging"). Modes of droplet motion in high-temperature gases area have been established. It has been determined the influence of the main droplet (sizes, composition, temperature, dispersability, form, velocity) and gas (temperature and velocity) characteristics on parameters of forming gas-vapor-droplet mixtures. The main elements of advanced firefighting technologies with the usage of time and space apportioned polydisperse composition water droplet flows have been formulated. Physical and predictive mathematical models have been developed to determine the basic parameters of equipment which is necessary for operation with these technology usage.

Volkov, Roman S.; Vysokomornaya, Olga V.; Zhdanova, Alyona O.; Strizhak, Pavel A.

2015-01-01

157

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

158

Dry phase of tropical lower stratospheric water vapor: Role of BDC, convection and ozone variability  

NASA Astrophysics Data System (ADS)

In the present paper, the relationship between dry phase of water vapor in the tropical lower stratosphere (TLS) and 100 hPa temperatures (T100) has been examined. Role of various processes, such as Brewer-Dobson circulation (BDC), convective activities and seasonal minimum of ozone mixing ratio, has been quantified to explain the reason of low T100 over Indonesian-Australian western Pacific region (IAWPR). Aura MLS data show that low water vapor mixing ratio (WVMR) first appears over the western Pacific during northern hemisphere (NH) winters and directs the dry phase of TLS. Observations of low T100 (~188 K), close association between WVMR and T100, slow transport of water vapor in TLS and saturation of air close to 82.5-100 hPa over IAWPR indicate conditions favorable for 'freeze drying'. Present analysis has brought out several interesting features (a) in addition to BDC, convective activities and low ozone mixing ratio near the tropopause level seems to be contributing to the low T100 over IAWPR during NH winter/spring, (b) apart from the seasonal decrease, T100 over IAWPR is noted to be continually low throughout the year by ~1.2 K than the zonal mean value where part of such decrease in T100 (i.e. ~0.7 K) can be understood in terms of water vapor feedback process and (c) wave activity of different temporal scale and amplitude (~1-2 K) also modulate T100 over IAWPR. MLS observations also provide an evidence of coupling between the surface and TLS processes, if the sea surface temperature over IAWPR is more than 301.7 K.

Jain, Shipra; Jain, A. R.; Mandal, T. K.

2014-12-01

159

Vapor-phase infrared spectroscopy on solid organic compounds with a pulsed resonant photoacoustic detection scheme  

NASA Astrophysics Data System (ADS)

There is a great need for a low cost and sensitive method to measure infrared spectra of solid organic compounds in the gas phase. To record such spectra, we propose an optical parametric generator-based photoacoustic spectrometer, which emits in the mid-infrared fingerprint region between 3 and 4 microns. In this system, the sample is heated in a vessel before entering a home built photoacoustic cell, where the gaseous molecules are excited by a tunable laser source with a frequency repetition rate that matches the first longitudinal resonance frequency of the photocaoustic cell. In a first phase, we have focused on low-melting point stimulants such as Nikethamide, Mephentermine sulfate, Methylephedrine, Ephedrine and Pseudoephedrine. The vapor-phase spectra of these doping substances were measured between 2800 and 3100 cm-1, where fundamental C-H stretching vibrations take place. Our spectra show notable differences with commercially available condensed phase spectra. Our scheme enables to measure very low vapor pressures of low-melting point (<160 °C) solid organic compounds. Furthermore, the optical resolution of 8 cm-1 is good enough to distinguish closely related chemical structures such as the Ephedra alkaloids Ephedrine and Methylephedrine, but doesn't allow to differentiate diastereoisomeric pairs such as Ephedrine and Pseudoephedrine, two important neurotransmitters which reveal different biological activities. Therefore, higher resolution and a system capable of measuring organic compounds with higher melting points are required.

Bartlome, Richard; Fischer, Cornelia; Sigrist, Markus W.

2005-08-01

160

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

161

High-quality single crystalline NiO with twin phases grown on sapphire substrate by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

High-quality single crystalline twin phase NiO grown on sapphire substrates by metalorganic vapor phase epitaxy is reported. X-ray rocking curve analysis of NiO films grown at different temperatures indicates a minimum full width at half maximum of the cubic (111) diffraction peak of 0.107° for NiO film grown at as low as 550 °C. Detailed microstructural analysis by ? scan X-ray diffraction and transmission electron microscopy reveal that the NiO film consists of large single crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60°. These single crystal domains are divided by the twin phase boundaries.

Uchida, Kazuo; Yoshida, Ken-ichi; Zhang, Dongyuan; Koizumi, Atsushi; Nozaki, Shinji

2012-12-01

162

Influence of gas phase equilibria on the chemical vapor deposition of graphene.  

PubMed

We have investigated the influence of gas phase chemistry on the chemical vapor deposition of graphene in a hot wall reactor. A new extended parameter space for graphene growth was defined through literature review and experimentation at low pressures (?0.001 mbar). The deposited films were characterized by scanning electron microscopy, Raman spectroscopy, and dark field optical microscopy, with the latter showing promise as a rapid and nondestructive characterization technique for graphene films. The equilibrium gas compositions have been calculated across this parameter space. Correlations between the graphene films grown and prevalent species in the equilibrium gas phase revealed that deposition conditions associated with a high acetylene equilibrium concentration lead to good quality graphene deposition, and conditions that stabilize large hydrocarbon molecules in the gas phase result in films with multiple defects. The transition between lobed and hexagonal graphene islands was found to be linked to the concentration of the monatomic hydrogen radical, with low concentrations associated with hexagonal islands. PMID:23484546

Lewis, Amanda M; Derby, Brian; Kinloch, Ian A

2013-04-23

163

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

164

New mechanism for autocatalytic decomposition of H2CO3 in the vapor phase.  

PubMed

In this article, we present high level ab initio calculations investigating the energetics of a new autocatalytic decomposition mechanism for carbonic acid (H2CO3) in the vapor phase. The calculation have been performed at the MP2 level of theory in conjunction with aug-cc-pVDZ, aug-cc-pVTZ, and 6-311++G(3df,3pd) basis sets as well as at the CCSD(T)/aug-cc-pVTZ level. The present study suggests that this new decomposition mechanism is effectively a near-barrierless process at room temperature and makes vapor phase of H2CO3 unstable even in the absence of water molecules. Our calculation at the MP2/aug-cc-pVTZ level predicts that the effective barrier, defined as the difference between the zero-point vibrational energy (ZPE) corrected energy of the transition state and the total energy of the isolated starting reactants in terms of bimolecular encounters, is nearly zero for the autocatalytic decomposition mechanism. The results at the CCSD(T)/aug-cc-pVTZ level of calculations suggest that the effective barrier, as defined above, is sensitive to some extent to the levels of calculations used, nevertheless, we find that the effective barrier height predicted at the CCSD(T)/aug-cc-pVTZ level is very small or in other words the autocatalytic decomposition mechanism presented in this work is a near-barrierless process as mentioned above. Thus, we suggest that this new autocatalytic decomposition mechanism has to be considered as the primary mechanism for the decomposition of carbonic acid, especially at its source, where the vapor phase concentration of H2CO3 molecules reaches its highest levels. PMID:24617952

Ghoshal, Sourav; Hazra, Montu K

2014-04-01

165

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. PMID:2106287

Klapes, N A; Vesley, D

1990-01-01

166

A field-space conformal-solution method: Binary vapor-liquid phase behavior  

NASA Astrophysics Data System (ADS)

The field-space conformal solution method provides an entirely new thermodynamic framework for the description of fluid mixtures in terms of the properties of a pure reference fluid. The utility and performance of the method are examined in the special case of vapor-liquid equilibrium correlation for simple mixtures. This is one of several cases in which field-space methods have numerical or theoretical advantages over methods presently used in mixture property correlation; only properties along the vapor pressure curve of the purefluid reference system are required for a complete description of the mixture phase behavior. Vapor-liquid equilibrium data for three binary hydrocarbon mixtures, n-butane + n-pentane, n-butane + n-hexane, and n-butane + n-octane, are correlated with a simple implementation of the method having two independent mixture parameters. Two pure-fluid equations of state, a Peng-Robinson equation and a 32-constant modified Benedict-Webb-Rubin equation, are tested as reference systems. The effects of differences in the quality of the reference system and of a range of mixture component size ratios are examined.

Storvick, T. S.; Fox, J. R.

1990-01-01

167

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

168

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

SciTech Connect

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 cm{sup 2}/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, E-mail: k.murakami@bk.tsukuba.ac.jp; Dong, Tianchen; Kajiwara, Yuya; Takahashi, Teppei; Fujita, Jun-ichi [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Tsukuba Research Center for Interdisciplinary Materials Science, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Hiyama, Takaki; Takai, Eisuke; Ohashi, Gai; Shiraki, Kentaro [Institute of Applied Physics, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan)

2014-06-16

169

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

170

DSC enthalpy of vaporization measurements of high temperature two-phase working fluids  

Microsoft Academic Search

The enthalpies of vaporization, saturated pressure-temperature behavior, and melting points for high-temperature (300–400°C) two-phase working fluids were measured using high-pressure DSC methodologies similar to those currently under development by ASTM E37. The materials, biphenyl, decafluorobiphenyl, o-terphenyl, naphthalene, quinoline, and perfluoro-1,3,5-triphenyl-benzene, were studied at seven pressures between 50 kPa and 1.4 MPa. The experimental measurements employed the use of a Mettler

Dwight D. Back; Lawrence R. Grzyll; Mary Corrigan

1996-01-01

171

High mobility electron-conducting thin-film transistors by organic vapor phase deposition  

NASA Astrophysics Data System (ADS)

In this letter, we report on the growth of thin films of N ,N'-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13H27) by organic vapor phase deposition (OVPD). Uniform films are deposited with a material utilization efficiency of 59±4% and deposition rates up to 15Å/s. Top-contact transistors based on OVPD-grown PTCDI-C13H27 show high n-type mobilities (up to 0.3cm2/Vs) and reproducible characteristics. The influence of deposition parameters on electrical properties is discussed.

Rolin, C.; Vasseur, K.; Schols, S.; Jouk, M.; Duhoux, G.; Müller, R.; Genoe, J.; Heremans, P.

2008-07-01

172

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

173

Development of advanced zeolite catalysts for the vapor phase Beckmann rearrangement of cyclohexanone oxime  

NASA Astrophysics Data System (ADS)

The vapor phase Beckmann rearrangement of cyclohexanone oxime to ?-caprolactam catalyzed by various zeolites was studied. The catalytic performance was greatly affected by both the zeolite structure and diluent solvent. When 1-hexanol was used in place of benzene, the catalytic performance of all catalysts except silicalite-1 was greatly improved. In particular, the selectivity and stability of H-LTL and H-OFF-ERI zeolites remarkably increased; both catalysts exhibited ca. 100% oxime conversion and ?-caprolactam selectivity of >95% for 6 h.

Dai, Lian-Xin; Iwaki, Yoshihide; Koyama, Katsuyuki; Tatsumi, Takashi

1997-11-01

174

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

175

Hydride vapor phase epitaxy of AlN using a high temperature hot-wall reactor  

NASA Astrophysics Data System (ADS)

Aluminum nitride (AlN) was grown on c-plane sapphire substrates by hydride vapor phase epitaxy (HVPE). The experiments utilized a two zone inductively heated hot-wall reactor. The surface morphology, crystal quality, and growth rate were investigated as a function of growth temperature in the range of 1450-1575 °C. AlN templates grown to a thickness of 1 ?m were optimized with double axis X-ray diffraction (XRD) rocking curve full width half maximums (FWHMs) of 135? for the (002) and 513? for the (102).

Baker, Troy; Mayo, Ashley; Veisi, Zeinab; Lu, Peng; Schmitt, Jason

2014-10-01

176

Thermodynamics of Si(OH)4 in the vapor phase of water: Henry’s and vapor-liquid distribution constants, fugacity and cross virial coefficients  

NASA Astrophysics Data System (ADS)

The fugacity coefficients of Si(OH)4 are evaluated from solubilities of solid phases of SiO2 in the vapor phase of water. The virial equation of state, truncated at the third virial coefficient, is employed to describe the fugacity coefficients of Si(OH)4. The temperature dependencies of the second, B12, and the third, C112, cross virial coefficients for H2O-Si(OH)4 interactions are approximated by empirical relations. It is found that silica-water interactions in the vapor phase are significantly more non-ideal compared to water-water interactions. Knowledge of B12 and C112 allows calculation of solubilities of quartz (Q) and amorphous silica (AS) in steam up to the density of 200 kg m-3 in satisfactory agreement with available data, and should provide reasonable solubility values at temperatures where no experimental results exist. The calculated values of the solubility of Q and AS in saturated vapor up to the critical temperature of water, Tc, are tabulated. The partial molar properties of dilute solutes close to the critical point of water are governed by the Krichevskii parameter, the value of which for Si(OH)4 is evaluated from available data (mainly vapor-liquid distribution constants for silica) to be equal to -187 ± 10 MPa. The knowledge of the thermodynamic properties of Si(OH)4 in the ideal gas state and in the state of the standard solution in liquid water allows calculating Henry’s constant, kH, for Si(OH)4 up to 623.15 K at water saturation pressure P1?. The theoretically-based equation, containing the Krichevskii parameter, allows extrapolating kH values all the way toward the critical temperature of water. This, in turn, makes possible calculation of the solubility of quartz and amorphous silica in liquid water at P1? at all temperatures up to Tc. The presented results should be useful for modeling solid-liquid-vapor, solid-vapor and liquid-vapor equilibria in the H2O-SiO2 system at steam densities up to 200 kg m-3.

Plyasunov, Andrey V.

2012-01-01

177

Long-lived chemiluminescence in cigarette smoke  

Microsoft Academic Search

Cigarette smoke contains high concentrations of unstable molecules that react with oxygen to produce chemiluminescence. The chemiluminescent activity concentrated in the aerosol phase that can be absorbed on glass-fiber filters and extracted into organic solvents. Cigarette smoke in N,N-dimethylformamide produces a long-lasting luminescence visible to the dark-adapted eye. We have demonstrated the oxygen dependence and have measured the kinetics, activation

H. H. Seliger; W. H. Biggley; J. P. Hamman

1974-01-01

178

Science and electronic cigarettes: current data, future needs.  

PubMed

Electronic cigarettes (ECIGs), also referred to as electronic nicotine delivery systems or "e-cigarettes," generally consist of a power source (usually a battery) and heating element (commonly referred to as an atomizer) that vaporizes a solution (e-liquid). The user inhales the resulting vapor. Electronic cigarettes have been increasing in popularity since they were introduced into the US market in 2007. Many questions remain about these products, and limited research has been conducted. This review describes the available research on what ECIGs are, effects of use, survey data on awareness and use, and the utility of ECIGs to help smokers quit using tobacco cigarettes. This review also describes arguments for and against ECIGs and concludes with steps to move research on ECIGs forward. PMID:25089952

Breland, Alison B; Spindle, Tory; Weaver, Michael; Eissenberg, Thomas

2014-01-01

179

Narrowband fiber-optic phase-shifted Fabry-Perot Bragg grating filters for atmospheric water vapor lidar measurements  

Microsoft Academic Search

A unique ultranarrowband fiber-optic phase-shifted Fabry-Perot Bragg grating filter for atmospheric water vapor lidar measurements was designed, fabricated, and successfully tested. Customized optical fiber Bragg gratings were fabricated so that two transmission filter peaks occurred: one (89% transmission, 8 pm FWHM) near the 946-nm water vapor absorption line and the other peak (80% transmission, 4 pm FWHM) at a region

Lelia B. Vann; Russell J. Deyoung; Stephen J. Mihailov; Ping Lu; Dan Grobnic; Robert Walker

2005-01-01

180

Vapor phase nitration of toluene over CuFe 0.8Al 1.2O 4  

Microsoft Academic Search

Vapor phase nitration of toluene by using CuFe0.8Al1.2O4 as a catalyst was studied by varying strength of nitric acid (10–69%) as a nitrating agent. Water vapor generated during the reaction acts as a diluent for the exothermic process. Varying the reaction temperature in the range of 100–200°C revealed that below 125°C lower conversion of toluene to mono-nitro toluene was obtained

Nivedita S. Chaubal; Manohar R. Sawant

2007-01-01

181

Observation of atomic carbon during photodissociation of nitrotoluenes in the vapor phase  

NASA Astrophysics Data System (ADS)

We perform laser-induced photodissociation fluorescence spectroscopy on mononitrotoluenes (MNTs) and dinitrotoluenes (DNTs) in the vapor phase and observe the spectrally overlapping fluorescence from nitric oxide (NO) and carbon (C). Energy-dispersive x-ray spectroscopy (EDS) and Raman spectroscopy of deposits found in the sample chamber confirm the presence of carbon. By comparing the observed fluorescence intensities with the Franck-Condon factors for NO, we are able to identify the presence or absence of fluorescence from carbon. 2-nitrotoluene and 4- nitrotoluene show carbon fluorescence for gate delays of up to 500 ns, while 2,4-dinitrotolune, 3,4-dinitrotolune, and 2,6-dinitrotolune show carbon fluorescence for gate delays of at least up to 1500 ns. The spectroscopic signal from atomic carbon in the vapor phase is observed at concentrations as low as 10 ppt. Based upon the observed S/N, detection at even lower concentrations appears feasible. Several non-nitrotoluene molecules including nitrobenzene, benzene, toluene, and CO2, are tested under identical conditions, but do not show any carbon emission. The presence of extra NO (simulation of NO pollutants) in the samples improves the S/N ratio for the detection of carbon. Energy transfer from laser-excited molecular nitrogen to NO, multiple decomposition channels in the electronic excited state of the nitrotoluene molecules, and interaction of NO with the excited-state decomposition process of the nitrotoluene molecules may all play a role.

Eilers, Hergen; Diez-y-Riega, Helena

2014-05-01

182

Insight into the structure of polymer-silica nano-composites prepared by vapor-phase.  

PubMed

Using a new synthesis technique, in which mesoporous Amberlite XAD7HP resin beads swollen with TEOS were exposed to vapors of either (H2O+HCl) or (H2O+NH3), we obtained smooth, porous, mechanically stable silica gel spheres after burning out the sacrificial organic template. Combined N2 sorption, SEM, TEM, (29)Si NMR, and Raman measurements were used to characterize the physical properties and molecular structures of the intermediate and final gels. Our atomically resolved TEM pictures provide the first visual demonstration of the presence of 3 to 6 member siloxane rings predicted by our Raman studies and other indirect methods. It is demonstrated that the physical appearance, morphology and porosity of the acid and base set gels are different from each other and also from those silica gels that were earlier polymerized from TEOS or Na-silicate saturated Amberlite XAD7HP with aqueous NH4OH or HCl solutions in liquid phase. We show that the different physical properties of the vapor-phase set gels are associated with different gelling rates at acidic and basic conditions, which generates molecular differences both in the intermediate and the final products. PMID:25490564

Halasz, Istvan; Kierys, Agnieszka; Goworek, Jacek

2015-03-01

183

The influence of temperature on the polymerization of ethyl cyanoacrylate from the vapor phase  

SciTech Connect

The polymerization of ethyl cyanoacrylate fumes from surface bound initiators is an important step in many novel and mature technologies. Understanding the effect of temperature on the rate of poly(ethyl cyanoacrylate) (PECA) growth and its molecular weight during its polymerization from the vapor phase from surface bound initiators provides insight into the important mechanistic aspects that impact the polymerizations success. In these studies, it is shown that the amount of PECA formed during the polymerization of ECA from a latent fingerprint increases with decreasing temperature, while the polymer molecular weight varies little. This is interpreted to be the result of the loosening of the ion pair that initiates the polymer chain growth and resides on the end of the growing polymer chain with decreasing temperature. Comparison of temperature effects and counter-ion studies show that in both cases loosening the ion pair results in the formation of more polymer with similar molecular weight, verifying this interpretation. These results further suggest that lowering the temperature may be an effective method to optimize anionic vapor phase polymerizations, including the improvement of the quality of aged latent prints and preliminary results are presented that substantiate this prediction.

Dadmun, Mark D [ORNL; Algaier, Dana [University of Tennessee, Knoxville (UTK); Baskaran, Durairaj [University of Tennessee, Knoxville (UTK)

2011-01-01

184

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

185

Compound nuclear decay and the liquid to vapor phase transition: a physical picture  

E-print Network

Analyses of multifragmentation in terms of the Fisher droplet model (FDM) and the associated construction of a nuclear phase diagram bring forth the problem of the actual existence of the nuclear vapor phase and the meaning of its associated pressure. We present here a physical picture of fragment production from excited nuclei that solves this problem and establishes the relationship between the FDM and the standard compound nucleus decay rate for rare particles emitted in first-chance decay. The compound thermal emission picture is formally equivalent to a FDM-like equilibrium description and avoids the problem of the vapor while also explaining the observation of Boltzmann-like distribution of emission times. In this picture a simple Fermi gas thermometric relation is naturally justified and verified in the fragment yields and time scales. Low energy compound nucleus fragment yields scale according to the FDM and lead to an estimate of the infinite symmetric nuclear matter critical temperature between 18 and 27 MeV depending on the choice of the surface energy coefficient of nuclear matter.

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

2005-07-08

186

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

NASA Astrophysics Data System (ADS)

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 m 3 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 m 3 g -1 d -1 with relative standard deviations of 8.4% and 8.6% respectively.

Cranor, Walter L.; Alvarez, David A.; Huckins, James N.; Petty, Jimmie D.

187

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

188

Fluid Phase Equilibria 243 (2006) 198205 Comment on "prediction of vapor pressures of solid organic  

E-print Network

of vapor pressures of solid organic compounds with a group contribution method" William E. Acree Jr gave satisfactory vapor pressure predictions for many organic compounds having vapor pressures well only for substituting into their predictive vapor pressure expression. The intent of this short

Chickos, James S.

189

On the existence of vapor-liquid phase transition in dusty plasmas  

SciTech Connect

The phenomenon of phase transition in a dusty-plasma system (DPS) has attracted some attention in the past. Earlier Farouki and Hamaguchi [J. Chem. Phys. 101, 9876 (1994)] have demonstrated the existence of a liquid to solid transition in DPS where the dust particles interact through a Yukawa potential. However, the question of the existence of a vapor-liquid (VL) transition in such a system remains unanswered and relatively unexplored so far. We have investigated this problem by performing extensive molecular dynamics simulations which show that the VL transition does not have a critical curve in the pressure versus volume diagram for a large range of the Yukawa screening parameter ? and the Coulomb coupling parameter ?. Thus, the VL phase transition is found to be super-critical, meaning that this transition is continuous in the dusty plasma model given by Farouki and Hamaguchi. We provide an approximate analytic explanation of this finding by means of a simple model calculation.

Kundu, M.; Sen, A.; Ganesh, R. [Institute for Plasma Research, Bhat, Gandhinagar 382 428, Gujarat (India); Avinash, K. [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

2014-10-15

190

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

191

On the existence of vapor-liquid phase transition in dusty plasmas  

NASA Astrophysics Data System (ADS)

The phenomenon of phase transition in a dusty-plasma system (DPS) has attracted some attention in the past. Earlier Farouki and Hamaguchi [J. Chem. Phys. 101, 9876 (1994)] have demonstrated the existence of a liquid to solid transition in DPS where the dust particles interact through a Yukawa potential. However, the question of the existence of a vapor-liquid (VL) transition in such a system remains unanswered and relatively unexplored so far. We have investigated this problem by performing extensive molecular dynamics simulations which show that the VL transition does not have a critical curve in the pressure versus volume diagram for a large range of the Yukawa screening parameter ? and the Coulomb coupling parameter ?. Thus, the VL phase transition is found to be super-critical, meaning that this transition is continuous in the dusty plasma model given by Farouki and Hamaguchi. We provide an approximate analytic explanation of this finding by means of a simple model calculation.

Kundu, M.; Avinash, K.; Sen, A.; Ganesh, R.

2014-10-01

192

E-Cigarettes Less Addictive Than Regular Cigarettes, Study Finds  

MedlinePLUS

... for both traditional cigarette smokers as well as electronic cigarette users," said Patricia Folan, director of the Center ... individual's past recollection of their addiction to traditional cigarettes ... electronic devices." The researchers received funding from Penn State ...

193

Controlling interfacial film formation in mixed polymer-surfactant systems by changing the vapor phase.  

PubMed

Here we show that transport-generated phase separation at the air-liquid interface in systems containing self-assembling amphiphilic molecules and polymers can be controlled by the relative humidity (RH) of the air. We also show that our observations can be described quantitatively with a theoretical model describing interfacial phase separation in a water gradient that we published previously. These phenomena arises from the fact that the water chemical potential corresponding to the ambient RH will, in general, not match the water chemical potential in the open aqueous solution. This implies nonequilibrium conditions at the air-water interface, which in turn can have consequences on the molecular organization in this layer. The experimental setup is such that we can control the boundary conditions in RH and thereby verify the predictions from the theoretical model. The polymer-surfactant systems studied here are composed of polyethylenimine (PEI) and hexadecyltrimethylammonium bromide (CTAB) or didecyldimethylammonium bromide (DDAB). Grazing-incidence small-angle X-ray scattering results show that interfacial phases with hexagonal or lamellar structure form at the interface of dilute polymer-surfactant micellar solutions. From spectroscopic ellipsometry data we conclude that variations in RH can be used to control the growth of micrometer-thick interfacial films and that reducing RH leads to thicker films. For the CTAB-PEI system, we compare the phase behavior of the interfacial phase to the equilibrium bulk phase behavior. The interfacial film resembles the bulk phases formed at high surfactant to polymer ratio and reduced water contents, and this can be used to predict the composition of interfacial phase. We also show that convection in the vapor phase strongly reduces film formation, likely due to reduction of the unstirred layer, where diffusive transport is dominating. PMID:25084476

Mokhtari, Tahereh; Pham, Quoc Dat; Hirst, Christopher; O'Driscoll, Benjamin M D; Nylander, Tommy; Edler, Karen J; Sparr, Emma

2014-08-26

194

Teenagers and E-cigarettes  

MedlinePLUS Videos and Cool Tools

... smoking and other risky behaviors. 29% of the teens said they had used e-cigarettes, a majority ... possibility that e-cigarettes are recruiting medium-risk adolescents to cigarette smoking who might otherwise be less ...

195

Vapor-deposited non-crystalline phase vs ordinary glasses and supercooled liquids: evidence for significant thermodynamic and kinetic differences  

E-print Network

Vapor deposition of molecules on a substrate often results in glassy materials of high kinetic stability and low enthalpy. The extraordinary properties of such glasses are attributed to high rates of surface diffusion during sample deposition, which makes it possible for constituents to find a configuration of much lower energy on a typical laboratory time scale1,2,7. The exact structure of the resulting phase is often assumed to be identical to that obtained by aging of ordinary glass over exceedingly long times. Using Fast Scanning Calorimetry technique, we show that out-of-equilibrium relaxation kinetics and possibly the enthalpy of vapor-deposited films of toluene, an archetypical fragile glass former, are distinct from those of ordinary supercooled phase even when the deposition takes place at temperatures above the glass softening. These observations provide support to the conjecture that the vapor-deposition may result in formation of non-crystalline phase of unique structural, thermodynamic, and kinetic properties.

Deepanjan Bhattacharya; Vlad Sadtchenko

2014-10-31

196

New cloud vapor zone (CVZ) coupled headspace solid-phase microextraction technique.  

PubMed

A new cloud vapor zone (CVZ)-based headspace solid-phase microextraction (HS-SPME) technique has been demonstrated with the capability of heating the sample matrix and simultaneously cooling the sampling zone. A bi-temperature-controlled (BTC) system, allowing 10 mL of test sample heating and headspace external-cooling, was employed for the CVZ formation around the SPME-fiber sampling area. In the CVZ procedure, the heated headspace vapor undergoes a sudden cooling near the SPME to form a dense cloud of analyte-water vapor, which is helpful for adsorption or absorption of the analyte. The device was evaluated for the quantitative analysis of aqueous chlorothalonil. Parameters influencing sampling efficiency, e.g., SPME fiber coating, SPME sampling temperature and time, solution modifier, addition of salt, sample pH, and temperature, were investigated and optimized thoroughly. The proposed BTC-HS-SPME method afforded a best extraction efficiency of above 94% accuracy (less than 4.1% RSD, n=7) by using the PDMS fiber to collect chlorothalonil in the headspace at 5 degrees C under the optimized condition, i.e., heating sample solution (added as 10% ethylene glycol and 30% NaCl, at pH 7.0) at 130 degrees C for 15 min. The detection was linear from 0.01 to 80 microg L-1 with a regression coefficient of 0.9998 and had a detection limit of 3.0 ng L-1 based on S/N=3. Practical application was demonstrated by analyzing chlorothalonil in farm water samples with promising results and recoveries. The approach provided a very simple, fast, sensitive, and solvent-free procedure to collect analytes from aqueous solution. The approach can provide a new platform for other sensitive HS-SPME assays. PMID:17356817

Huang, Yi-Ching; Su, Yi-Song; Muniraj, Sarangapani; Zhang, Weibing; Jen, Jen-Fon

2007-05-01

197

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

198

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

199

The intractable cigarette ‘filter problem’  

Microsoft Academic Search

BackgroundWhen 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

Bradford Harris

2011-01-01

200

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

201

The Effect Of ZnO Addition On Co/C Catalyst For Vapor And Aqueous Phase Reforming Of Ethanol  

SciTech Connect

The effect of ZnO addition on the oxidation behavior of Co along with catalytic performance in vapor and aqueous phase reforming of ethanol were investigated on Co supported on carbon black (XC-72R). Carbon was selected to minimize the support interactions. Effect of ZnO addition during both vapor and aqueous phase reforming were compared at 250 °C. ZnO addition inhibited the reduction of cobalt oxides by H2 and created surface sites for H2O activation. During vapor phase reforming at 450 °C the redox of cobalt, driven by steam oxidation and H2 reduction, trended to an equilibrium of Co0/Co2+. ZnO showed no significant effect on cobalt oxidation, inferred from the minor changes of C1 product yield. Surface sites created by ZnO addition enhanced water activation and oxidation of surface carbon species, increasing CO2 selectivity. At 250 °C cobalt reduction was minimal, in situ XANES demonstrated that ZnO addition significantly facilitated oxidation of Co0 under vapor phase reforming conditions, demonstrated by lower C1 product yield. Sites introduced by ZnO addition improved the COx selectivity at 250 °C. Both Co/C and Co-ZnO/C rapidly oxidized under aqueous phase reaction conditions at 250 °C, showing negligible activity in aqueous phase reforming. This work suggests that ZnO affects the activation of H2O for Co catalysts in ethanol reforming.

Davidson, Stephen; Sun, Junming; Hong, Yongchun; Karim, Ayman M.; Datye, Abhaya K.; Wang, Yong

2014-02-05

202

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

203

Tuning aerosol-assisted vapor phase processing towards low oxygen GaN powders  

NASA Astrophysics Data System (ADS)

Herein, are reported studies of various experimental conditions aimed at optimizing the Aerosol-Assisted Vapor Phase Synthesis (AAVS) of GaN powders. In general, the process utilizes affordable oxygen-bearing gallium precursors in aqueous/methanol solutions to initially prepare nano-sized GaNx Oy powders of spheroidal morphology. Subsequent pyrolysis of the GaNx Oy intermediate in a NH3 atmosphere converts the powders to sub-micron, crystalline GaN powders that usually contain some residual oxygen. The application of appropriate solvents, e.g. , methanol, in the aerosol powder generation stage and the use of pyrolysis temperatures in the range 900-1000 °C may improve both the extent of nitridation and, to certain degree, the control over average particle sizes. The characteristics of the AAVS-produced materials are compared with those for bulk GaN powders obtained by direct nitridation of commercial gallium oxide.

Janik, J. F.; Dryga, M.; Stelmakh, S.; Grzanka, E.; Paosz, B.; Paine, R. T.

2006-05-01

204

Direct frequency modulation of vapor phase transported distributed feedback semiconductor lasers  

SciTech Connect

The frequency modulation (FM) due to injection current modulation of vapor phase transported distributed feedback (VPT DFB) semiconductor lasers is measured as a function of modulation frequency from 10 kHz to 1 GHz. A large frequency modulation response of 350 MHz/mA is obtained for the modulation frequency range of 10 to 1000 MHz. Demodulation of optical frequency shift keying (FSK) at 560 Mb/s is demonstrated, indicating that frequency modulation due to thermal modulation does not pose a significant limitation at this bit rate or higher. The large FM response together with modulation bandwidths up to 8 GHz makes the VPT DFB laser an attractive source for high bit rate optical FSK transmission.

Vodhanel, R.S.; Cheung, N.K.; Koch, T.L.

1986-04-14

205

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

206

Nonpolar GaN grown on Si by hydride vapor phase epitaxy using anodized Al nanomask  

NASA Astrophysics Data System (ADS)

GaN growth by the hydride vapor phase technique on (100) Si substrates masked by porous Al anodic oxide is described. The masks were prepared by vacuum deposition of Al with subsequent anodic oxidation in dilute sorrel acid. The grown GaN layer is nonpolar, with (112¯0) a-orientation and a full width at half maximum of the (112¯0) reflection below 500 arc sec and showing small anisotropy. This result is comparable with the results obtained for a-GaN growth using selective epitaxy or advanced buffer growth routines. Microcathodoluminescence spectra of the grown films confirm a low density of stacking faults. Possible growth mechanisms are discussed.

Polyakov, A. Y.; Markov, A. V.; Mezhennyi, M. V.; Govorkov, A. V.; Pavlov, V. F.; Smirnov, N. B.; Donskov, A. A.; D'yakonov, L. I.; Kozlova, Y. P.; Malakhov, S. S.; Yugova, T. G.; Osinsky, V. I.; Gorokh, G. G.; Lyahova, N. N.; Mityukhlyaev, V. B.; Pearton, S. J.

2009-01-01

207

Homoepitaxial growth of ?-Ga2O3 layers by halide vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Thick high-purity ?-Ga2O3 layers of high crystalline quality were grown homoepitaxially by halide vapor phase epitaxy (HVPE) using gaseous GaCl and O2 on (001) ?-Ga2O3 substrates prepared by edge-defined film-fed growth. The surface morphology and structural quality of the grown layer improved with increasing growth temperature. X-ray diffraction ?-rocking curves for the (002) and (400) reflections for the layer grown at 1000 °C had small full widths at half maximum. Secondary ion mass spectrometry and electrical characteristics revealed that the growth of high-purity ?-Ga2O3 layers with low effective donor concentration (Nd ? Na < 1013 cm?3) is possible by HVPE.

Murakami, Hisashi; Nomura, Kazushiro; Goto, Ken; Sasaki, Kohei; Kawara, Katsuaki; Thieu, Quang Tu; Togashi, Rie; Kumagai, Yoshinao; Higashiwaki, Masataka; Kuramata, Akito; Yamakoshi, Shigenobu; Monemar, Bo; Koukitu, Akinori

2015-01-01

208

Detection of condensed-phase explosives via laser-induced vaporization, photodissociation, and resonant excitation.  

PubMed

We investigate the remote detection of explosives via a technique that vaporizes and photodissociates the condensed-phase material and detects the resulting vibrationally excited NO fragments via laser-induced fluorescence. The technique utilizes a single 7 ns pulse of a tunable laser near 236.2 nm to perform these multiple processes. The resulting blue-shifted fluorescence (226 nm) is detected using a photomultiplier and narrowband filter that strongly block the scatter of the pump laser off the solid media while passing the shorter wavelength photons. Various nitro-bearing compounds, including 2,6-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) were detected with a signal-to-noise of 25 dB. The effects of laser fluence, wavelength, and sample morphology were examined. PMID:19122718

Wynn, C M; Palmacci, S; Kunz, R R; Clow, K; Rothschild, M

2008-11-01

209

Treatment of Produced Waters Using a Surfactant Modified Zeolite/Vapor Phase Bioreactor System  

SciTech Connect

This report summarizes work of this project from October 2003 through March 2004. The major focus of the research was to further investigate BTEX removal from produced water, to quantify metal ion removal from produced water, and to evaluate a lab-scale vapor phase bioreactor (VPB) for BTEX destruction in off-gases produced during SMZ regeneration. Batch equilibrium sorption studies were conducted to evaluate the effect of semi-volatile organic compounds commonly found in produced water on the sorption of benzene, toluene, ethylbenzene, and xylene (BTEX) onto surfactant-modified zeolite (SMZ) and to examine selected metal ion sorption onto SMZ. The sorption of polar semi-volatile organic compounds and metals commonly found in produced water onto SMZ was also investigated. Batch experiments were performed in a synthetic saline solution that mimicked water from a produced water collection facility in Wyoming. Results indicated that increasing concentrations of semi-volatile organic compounds increased BTEX sorption. The sorption of phenol compounds could be described by linear isotherms, but the linear partitioning coefficients decreased with increasing pH, especially above the pKa's of the compounds. Linear correlations relating partitioning coefficients of phenol compounds with their respective solubilities and octanol-water partitioning coefficients were developed for data collected at pH 7.2. The sorption of chromate, selenate, and barium in synthetic produced water were also described by Langmuir isotherms. Experiments conducted with a lab-scale vapor phase bioreactor (VPB) packed with foam indicated that this system could achieve high BTEX removal efficiencies once the nutrient delivery system was optimized. The xylene isomers and benzene were found to require the greatest biofilter bed depth for removal. This result suggested that these VOCs would ultimately control the size of the biofilter required for the produced water application. The biofilter recovered rapidly from shutdowns showing that the system was resilient to discontinuous feed conditions therefore provided flexibility on the SMZ regeneration process.

Lynn E. Katz; Kerry A. Kinney; R. S. Bowman; E. J. Sullivan

2004-03-11

210

Vapor phase toxicity of marjoram oil compounds and their related monoterpenoids to Blattella germanica (Orthoptera: Blattellidae).  

PubMed

The toxicity of marjoram, Origanum majorana L., oil, 41 monoterpenoids, and 2 sesquiterpenoids against adult females of the German cockroach, Blattella germanica L., was examined using direct contact and vapor phase toxicity bioassays and compared with those of deltamethrin, dichlorvos, permethrin, and propoxur, four commonly used insecticides. In a filter-paper contact toxicity bioassay, the adulticidal activities of pulegone (0.06 mg/cm2), (+/-)-camphor (0.07 mg/cm2), and verbenone (0.07 mg/cm2) were comparable to that of permethrin (0.05 mg/cm2) but more pronounced than that of propoxur (0.18 mg/cm2), as judged by the 24-h LC50 values. These compounds were less effective than either deltamethrin (0.013 mg/cm2) or dichlorvos (0.007 mg/cm2). The toxicity of marjoram oil, thymol, alpha-terpineol, (-)-alpha-thujone, linalool, 1,8-cineole, (-)-camphor, and (+)-carvone, ranging from 0.08 to 0.18 mg/cm2, was higher than that of propoxur. In vapor phase toxicity tests, verbenone (11.48 mg/L air) was the most toxic compound followed by (-)-alpha-thujone (18.43 mg/L of air), thymol (18.76 mg/L of air), alpha-terpineol (21.89 mg/L of air), (+/-)-camphor (24.59 mg/L of air), linalool (26.20 mg/L of air), and marjoram oil (38.28 mg/L of air) on the basis of the 24-h LC50 values. Dichlorvos (0.07 mg/L of air) was the most potent fumigant. Structure-activity relationships indicate that structural characteristics, such as degrees of saturation and types of functional groups rather than types of carbon skeleton, and hydrophobicity and vapor pressure parameters appear to play a role in determining the monoterpenoid toxicities to adult B. germanica. Marjoram oil and the monoterpenoids described merit further study as potential fumigants or leads for the control of B. germanica. PMID:16190647

Jang, Young-Su; Yang, Young-Cheol; Choi, Dal-Soon; Ahn, Young-Joon

2005-10-01

211

Cigarettes Health Risks  

E-print Network

Cigarettes Health Risks Smoking is the single greatest avoidable cause of disease and death lung disease. New studies have shown that about half of all regular cigarette smokers die percent of these deaths are from cancer, 35 percent from heart disease and stroke, and 25 percent from

Oregon, University of

212

Phase evolution in low-pressure Se vapor selenization of evaporated Cu/In bilayer precursors  

NASA Astrophysics Data System (ADS)

Evolution of elemental binaries and single-phase copper indium diselenide, CuInSe2 (CIS) during Se vapor selenization of evaporated Cu/In bilayer metal precursors at pressures of 0.3-10 mbar and temperatures in the range of 260-400 °C has been investigated. At low pressures, the relative kinetics of selenization of Cu and In are changed resulting in the formation of single-phase CIS even at very low temperatures (260 °C). Optical, Auger, and x-ray photoelectron spectroscopy investigations are employed to characterize the chalcopyrite absorber layer. At higher pressures (?7-10 mbar), simultaneous formation of the equilibrium binaries, CuSe and In2Se3 at low temperatures leads to the formation of CIS through a diffusion limited reaction of the binaries at higher temperatures. The availability of Se reacting species varies significantly in the pressure regime. At low reactor pressures and Se availability, the reaction CuSe+In(l)+Se?CIS, proceeds to completion even at low temperatures. The detailed study of the phase evolution is made by x-ray diffraction and scanning electron microscopy investigations and correlated with the Se availability in the reactor.

Lakshmikumar, S. T.; Rastogi, A. C.

1996-04-01

213

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...

214

Electronic cigarettes (E-cigarettes) are devices that deliver nicotine  

E-print Network

e490 Electronic cigarettes (E-cigarettes) are devices that deliver nicotine to a user by heating of smoking).4,5 Thus, use of electronic cigarettes to cut (Circulation. 2014;129:e490-e492.) © 2014 American, flavoring chemicals, and nicotine1 (Figure). E-cigarette use dou- bled in just 1 year among both adults

Derisi, Joseph

215

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

216

Formation of etch pits during carbon doping of gallium arsenide with carbon tetrachloride by metalorganic vapor-phase epitaxy  

E-print Network

by the metalorganic vapor-phase epitaxy MOVPE of GaAs using carbon tetrachloride CCl4) or trimethylgal- lium TMGa have focused on the acceptor levels and growth rates obtained as a function of CCl4 concentration the kinetics of CCl4 decomposi- tion during the MOVPE of GaAs and InAs.19 It was found that adsorbed chlorine

Li, Lian

217

Antimicrobial effects of vapor phase thymol, modified atmosphere and their combination against Salmonella spp. on raw shrimp  

Technology Transfer Automated Retrieval System (TEKTRAN)

Salmonella contamination of raw shrimp is a food safety concern in the U.S. and other countries. This research evaluated the effects of vapor phase thymol, modified atmosphere (MA) and their combination against Salmonella spp. on raw shrimp. Growth profiles of a Salmonella spp. cocktail (6 strains),...

218

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

E-print Network

Potential phase control of chromium oxide thin films prepared by laser-initiated organometallic used laser-initiated chemical vapor deposition to grow the chromium oxide thin films through chromium oxide CrO2 with Tc 397 K Ref. 5 has been predicted to be half metallic metallic for one spin

Idzerda, Yves

219

Vapor-phase catalytic oxidesulfurization (ODS) of organosulfur compounds over supported metal oxide catalysts  

NASA Astrophysics Data System (ADS)

Sulfur in transportation fuels remains a leading source of SOx emissions from vehicle engines and is a major source of air pollution. The very low levels of sulfur globally mandated for transportation fuels in the near future cannot be achieved by current practices of hydrodesulfurization (HDS) for sulfur removal, which operate under severe conditions (high T, P) and use valuable H2. Novel vapor-phase catalytic oxidesulfurization (ODS) processes of selectively oxidizing various organosulfur compounds (carbonyl sulfide, carbon disulfide, methanethiol, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), thiophene, 2,5-dimenthylthiophene) typically found in various industrial streams (e.g., petroleum refining, pulp and paper) into valuable chemical intermediates (H 2CO, CO, H2, maleic anhydride and concentrated SO2) has been extensively studied. This research has primarily focused on establishing the fundamental kinetics and mechanisms of these selective oxidation reactions over well-defined supported metal oxide catalysts. The selective oxidation reactions of COS + O2 ? CO + SO2; 2CS2 + 5O2 ? 2CO + 4SO2; CH3SH + 2O 2 ? H2CO + SO2 + H2O; C4 H4S + 3O2 ? C4H2O 3 + H2O + SO2; were studied. Raman spectroscopy revealed that the supported metal oxide phases were 100% dispersed on the oxide substrate. All the catalysts were highly active and selective for the oxidesulfurization of carbonyl sulfide, carbon disulfide, methanethiol, and thiophene between 290--330°C, 230--270°C, 350--400°C, and 250--400°C, respectively and did not deactivate. The TOFs (turnover frequency, normalized activity per active catalytic site) for all ODS reactions over supported vanadia catalysts, only containing molecularly dispersed surface vanadia species, varied within one order of magnitude and revealed the V-O-Support bridging bond was involved in the critical rate-determining kinetic steps. The surface reaction mechanism for each reaction was revealed by in situ IR (infrared) and temperature programmed surface reaction-mass spectroscopy (TPSR-MS). The systematic investigation of vapor-phase oxidesulfurization (ODS) reactions of organosulfur compounds over catalytic supported metal oxides revealed the facile S-O exchange mechanisms allow for the efficient removal of sulfur while producing value-added chemicals and represents the discovery of a new series of catalytic reactions.

Choi, Sukwon

220

Application of a newly developed hydrogen peroxide vapor phase sensor to HPV sterilizer.  

PubMed

A new type of concentration sensor for hydrogen peroxide vapor has been developed by making use of a semiconductor. Output from the vapor sensor has been shown to have a good linear relationship with the logarithm of the concentration of hydrogen peroxide vapor. Concentration of hydrogen peroxide vapor introduced into the sterilization chamber could be kept constant by monitoring the concentration of the hydrogen peroxide vapor continuously and controlling the vapor supply. Temperature and humidity have also been kept constant. D-values for B. stearothermophilus ATCC 12980 at various concentrations of hydrogen peroxide vapor have been determined by using the combination system of the hydrogen peroxide vapor sensor, the hydrogen peroxide vapor supplier, thermosensor and humidity sensor. D-values at the temperature of 30 degrees C and the absolute humidity of 0.7 mg H2O/L thus obtained, were 0.2 minutes at hydrogen peroxide concentration of 600 ppm and 1.2 minutes at 200 ppm at the temperature of 30 degrees C and 0.7 mg/L absolute humidity. D-values for B. stearothermophilus ATCC 12980 at various temperatures, humidity and levels of hydrogen peroxide concentration have also been determined. These fundamental data indicate that the sterilization by hydrogen peroxide vapor can be validated as precisely as steam sterilization by measuring and controlling the concentration of hydrogen peroxide vapor using a combination of the hydrogen peroxide concentration sensor and the vapor generator. Influence of temperature and humidity have also been studied. The hydrogen peroxide sensor has been calibrated and standardized by using the standard hydrogen peroxide vapor whose concentration has been determined by calculating partial pressure of hydrogen peroxide over the water-hydrogen peroxide solution. PMID:9542409

Taizo, I; Sinichi, A; Kawamura, K

1998-01-01

221

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

222

Magnetic resonance imaging of nonaqueous phase liquid during soil vapor extraction in heterogeneous porous media.  

PubMed

Soil vapor extraction (SVE) is commonly used to remediate nonaqueous phase liquids (NAPLs) from the vadose zone. This paper aims to determine the effect of grain size heterogeneity on the removal of NAPL in porous media during SVE. Magnetic resonance imaging (MRI) was used to observe and quantify the amount and location of NAPL in flow-through columns filled with silica gel grains. MRI is unique because it is nondestructive, allowing three-dimensional images to be taken of the phases as a function of space and time. Columns were packed with silica gel in three ways: coarse grains (250-550 microm) only, fine grains (32-63 microm) only, and a core of fine grains surrounded by a shell of coarse grains. Columns saturated with water were drained under a constant suction head, contaminated with decane, and then drained to different decane saturations. Each column was then continuously purged with water-saturated nitrogen gas and images were taken intermittently. Results showed that at residual saturation, a sharp volatilization front moved through the columns filled with either coarse-grain or fine-grain silica gel. In the heterogeneous columns, the volatilization front in the core lagged just behind the shell because gas flow was greater through the shell and decane in the core diffused outward to the shell. When decane saturation in the core was above residual saturation, decane volatilization occurred near the inlet, the relative decane saturation throughout the core dropped uniformly, and decane in the core flowed in the liquid phase to the shell to replenish volatilized decane. These results indicate that NAPL trapped in low-permeability zones can flow to replenish areas where NAPL is lost due to SVE. However, when residual NAPL saturation is reached, NAPL flow no longer occurs and diffusion limits removal from low-permeability zones. PMID:15336788

Chu, Yanjie; Werth, Charles J; Valocchi, Albert J; Yoon, Hongkyu; Webb, Andrew G

2004-09-01

223

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

224

Sol–gel synthesis of MCM-41 silicas and selective vapor-phase modification of their surface  

SciTech Connect

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. - Graphical abstract: Sol–gel synthesis and postsynthetic chemical modification of template-filled MCM-41 and Cl-MCM-41 with (3-chloropropyl)triethoxysilane and 1,2-ethylenediamine in vapor phase. Display Omitted - Highlights: • Synthesis of MCM-41 silica by template directed sol–gel condensation. • Selective vapor-phase functionalization of template-filled silica particles. • Preferential localization of grafted groups onto the exterior surface of mesoporous silicas.

Roik, N.V., E-mail: roik_nadya@ukr.net; Belyakova, L.A.

2013-11-15

225

Narrow band fiber-optic phase-shifted Fabry-Perot Bragg grating filters for atmospheric water vapor lidar measurements.  

PubMed

A unique ultranarrowband fiber-optic phase-shifted Fabry-Perot Bragg grating filter for atmospheric water vapor lidar measurements was designed, fabricated, and successfully tested. Customized optical fiber Bragg gratings were fabricated so that two transmission filter peaks occurred: one (89% transmission, 8 pm FWHM) near the 946-nm water vapor absorption line and the other peak (80% transmission, 4 pm FWHM) at a region of no absorption. Both transmission peaks were within a 2.66-nm stop band. Demonstration of tension tuning to the 946.0003-nm water vapor line was achieved, and the performance characterization of custom-made optical fiber Bragg grating filters are presented. These measurements are successfully compared to theoretical calculations using a piecewise-matrix form of the coupled-mode equations. PMID:16353809

Vann, Lelia B; DeYoung, Russell J; Mihailov, Stephen J; Lu, Ping; Grobnic, Dan; Walker, Robert

2005-12-01

226

Spectroscopic determination of enthalpies of sublimation of organic materials in the vapor phase: Benzoic acid, ferrocene, and naphthalene  

NASA Astrophysics Data System (ADS)

Techniques for determining the enthalpies of sublimation of low volatile materials in the vapor phase are quite rare. Although benzoic acid, ferrocene, and naphthalene are used as reference materials for indirect determination of vapor pressure of volatile materials, the discrepancy of the values of their enthalpies of sublimation is considerably large (˜10-15 kJ/mol). In this work, the enthalpies of sublimation of vapors of these materials are determined using absorbance spectroscopy in the ultraviolet region of the electromagnetic spectrum. This methodology is based on the linear proportionality between the density of the saturated gas of the material and the absorbance of the gas. The determined values of enthalpies of sublimation are in excellent agreement with the mean value of those reported in literature and those recommended by the ICTAC. This method is shown to be accurate and rapid.

Hikal, Walid M.; Weeks, Brandon L.

2013-03-01

227

Investigation by microarray analysis of effects of cigarette design characteristics on gene expression in human lung mucoepidermoid cancer cells NCI-H292 exposed to cigarette smoke.  

PubMed

The effects of tobacco leaf types and the presence or absence of charcoal in the cigarette filters on gene expression were investigated using cigarette prototypes made of either flue-cured (FC) leaf or burley (BLY) leaf and Kentucky Reference 2R4F as a representative blend cigarette with cellulose acetate filters or charcoal filters. NCI-H292, human lung mucoepidermoid carcinoma cell line, was exposed to the total particulate matter (TPM) and gas/vapor phase (GVP) from each prototype for 8h and then the changes in gene expression from microarray data were analyzed. A number of genes associated with oxidative stress, inflammation, DNA damage and xenobiotic response were modified by the two fractions, TPM and GVP, from the three prototypes with cellulose acetate filters. Both TPM and GVP fractions strongly enhanced the gene expression of HMOX1, which is encoding the limiting enzyme in heme degradation and a key regulator of oxidative stress and inflammatory process. Comparing the effects of TPM and GVP fraction, TPM strongly activated Nrf2 pathway-mediated anti-oxidative stress reaction, whereas GVP caused notable DNA damage response. In comparison of FC and BLY, TPM from FC more strongly induced the expression of histone family proteins than that from BLY. GVP from FC markedly induced gene expression associated with HSP70-mediated inflammation relative to that from BLY. Charcoal included in the filter strongly reduced the effects of GVP from each cigarette on gene expression. However, charcoal did not modified the effects of TPM. As a whole, charcoal is a useful material for reducing the biological effects of GVP. PMID:25497788

Sekine, Takashi; Sakaguchi, Chikako; Fukano, Yasuo

2015-02-01

228

Towards large area and continuous MoS2 atomic layers via vapor-phase growth: thermal vapor sulfurization  

NASA Astrophysics Data System (ADS)

We report on the effects of substrate, starting material, and temperature on the growth of MoS2 atomic layers by thermal vapor sulfurization in a tube-furnace system. With Mo as the starting material, atomic layers of MoS2 flakes are obtained on sapphire substrates while a bell-shaped MoS2 layer, sandwiched by amorphous SiO2, is obtained on native-SiO2/Si substrates under the same sulfurization conditions. An anomalous thickness-dependent Raman shift (A1g) of the MoS2 atomic layers is observed in Mo-sulfurizations on sapphire substrates, which can be attributed to the competition between the effects of thickness and the surface/interface. Both effects vary with the sulfurizing temperatures for a certain initial Mo thickness. The anomalous frequency trend of A1g is missing when using MoO3 instead of Mo as the starting material. In this case, the lateral growth of MoS2 on sapphire is also largely improved. Furthermore, the area density of the resultant MoS2 atomic layers is significantly increased by increasing the deposition temperature of the starting MoO3 to 700 °C the adjacent ultrathin MoS2 grains coalesce in one or other direction, forming connected chains in wafer scale. The thickness of the so-obtained MoS2 is generally controlled by the thickness of the starting material; however, the structural and morphological properties of MoS2 grains, towards large area and continuous atomic layers, are strongly dependent on the temperature of the initial material deposition, and on the temperature of sulfurization, because of the competition between surface mobility and atom evaporation.

Liu, Hongfei; Ansah Antwi, K. K.; Ying, Jifeng; Chua, Soojin; Chi, Dongzhi

2014-10-01

229

Enhancing the adsorption of vapor-phase mercury chloride with an innovative composite sulfur-impregnated activated carbon.  

PubMed

Mercury chloride (HgCl(2)) is the major mercury derivate emitted from municipal solid waste incinerators, which has high risk to the environment and human health. This study investigated the adsorption of vapor-phase HgCl(2) with an innovative composite sulfurized activated carbon (AC), which was derived from the pyrolysis, activation, and sulfurization of waste tires. The composite sulfur-impregnation process impregnated activated carbon with aqueous-phase sodium sulfide (Na(2)S) and followed with vapor-phase elemental sulfur (S(0)). Thermogravimetric analysis (TGA) was applied to investigate the adsorptive capacity of vapor-phase HgCl(2) using the composite sulfurized AC. The operating parameters included the types of composite sulfurized AC, the adsorption temperature, and the influent HgCl(2) concentration. Experimental results indicated that the sulfur-impregnation process could increase the sulfur content of the sulfurized AC, but decreased its specific surface area. This study further revealed that the composite sulfurized AC impregnated with aqueous-phase Na(2)S and followed with vapor-phase S(0) (Na(2)S+S(0) AC) had much higher saturated adsorptive capacity of HgCl(2) than AC impregnated in the reverse sequence (S(0)+Na(2)S AC). A maximum saturated adsorptive capacity of HgCl(2) up to 5236 ?g-HgCl(2)/g-C was observed for the composite Na(2)S+S(0) AC, which was approximately 2.00 and 3.17 times higher than those for the single Na(2)S and S(0) ACs, respectively. PMID:22410724

Ie, Iau-Ren; Chen, Wei-Chin; Yuan, Chung-Shin; Hung, Chung-Hsuang; Lin, Yuan-Chung; Tsai, Hsieh-Hung; Jen, Yi-Shiu

2012-05-30

230

Toxicological assessment of kretek cigarettes part 4: Mechanistic investigations, smoke chemistry and invitro toxicity.  

PubMed

The smoke chemistry and in vitro toxicity of mainstream smoke (MS) was investigated in American-blended cigarettes with or without the addition of 2.5%, 5% or 10% eugenol to the tobacco and in Indonesian-blended cigarettes with and without the addition of cloves, cloves extracted with hot ethanol, and extracted cloves replenished with eugenol or clove oil. The addition of eugenol reduced the concentration of nearly all toxicants measured in MS as well as the in vitro cytotoxicity of the gas/vapor phase. Reductions were also seen in bacterial mutagenicity of the total particulate matter (TPM) assessed by the Ames Assay. The addition of extracted cloves led to increases and decreases of toxicant concentrations in MS. Replenishment with eugenol or clove oil decreased the toxicant concentrations; with most smoke constituent concentrations reduced below the concentration found in tobacco-only cigarettes. Cytotoxicity of the TPM was not affected by the clove preparations. However, GVP cytotoxicity was reduced (untreated cloves showing the highest reductions). Mutagenicity of TPM was decreased by the clove preparations. Mechanisms for the reductions, (up to 40%), are most likely due to dilution effects by eugenol, changed burning characteristics of the tobacco, and free radical scavenging by eugenol. PMID:25455230

Roemer, E; Dempsey, R; Lawless-Pyne, J; Lukman, S; Evans, A Deger; Trelles-Sticken, E; Wittke, S; Schorp, M K

2014-12-01

231

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

232

Carbon-Supported bimetallic Pd-Fe catalysts for vapor-phase hydrodeoxygenation of guaiacol  

SciTech Connect

Abstract Carbon supported metal catalysts (Cu/C, Fe/C, Pd/C, Pt/C, PdFe/C and Ru/C) have been prepared, characterized and tested for vapor-phase hydrodeoxygenation (HDO) of guaiacol (GUA) at atmospheric pressure. Phenol was the major intermediate on all catalysts. Over the noble metal catalysts saturation of the aromatic ring was the major pathway observed at low temperature (250 °C), forming predominantly cyclohexanone and cyclohexanol. Substantial ring opening reaction was observed on Pt/C and Ru/C at higher reaction temperatures (e.g., 350 °C). Base metal catalysts, especially Fe/C, were found to exhibit high HDO activity without ring-saturation or ring-opening with the main products being benzene, phenol along with small amounts of cresol, toluene and trimethylbenzene (TMB). A substantial enhancement in HDO activity was observed on the PdFe/C catalysts. Compared with Fe/C, the yield to oxygen-free aromatic products (i.e., benzene/toluene/TMB) on PdFe/C increased by a factor of four at 350 °C, and by approximately a factor of two (83.2% versus 43.3%) at 450 °C. The enhanced activity of PdFe/C is attributed to the formation of PdFe alloy as evidenced by STEM, EDS and TPR.

Sun, Junming; Karim, Ayman M.; Zhang, He; Kovarik, Libor; Li, Xiaohong S.; Hensley, Alyssa; McEwen, Jean-Sabin; Wang, Yong

2013-10-01

233

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

234

Metal organic vapor phase epitaxy (MOVPE) grown heterojunction diodes in Hg1-xCdxTe  

NASA Astrophysics Data System (ADS)

Recent advances in the growth of cadmium mercury telluride (Hg1-xCdxTe or MCT) by metal organic vapor phase epitaxy (MOVPE) allow the fabrication of advanced device structures where both the alloy composition x and the doping concentration can be accurately controlled throughout the epitaxial layer. For p-type doping using arsenic, the acceptor concentration can be varied from 5 X 1015 cm-3 to 4 X 1017 cm-3 and for n-type doping using iodine, the donor concentration can be varied from 1 X 1015 cm-3 to 2 X 1017 cm-3. A number of diode arrays have been fabricated in this material and their properties assessed at 77 K, 195 K and 295 K. It has been found that the diffusion currents are at least ten times lower than in homojunctions. In addition, the devices exhibit negative resistance at temperatures above 190 K due to auger suppression. The successful demonstration of auger suppression in these structures has greatly improved the diode leakage currents at room temperature and will enable the development of new devices such as a room temperature laser detector.

Elliott, Charles T.; Gordon, Neil T.; Hall, R. S.; Phillips, T. J.; Jones, C. L.; Matthews, B. E.; Maxey, C. D.; Metcalfe, N. E.

1994-10-01

235

Ultraviolet Light Emitting Diode with High Quality Epilayer Grown by Hydride Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

In this paper, the selective area growth (SAG) of SAG-UV light-emitting diode (LED) was performed by mixed-source hydride vapor phase epitaxy (HVPE) with a multi-sliding boat system. The SAG-UV LED consists of a Si-doped GaN layer, an Si-doped AlGaN cladding layer, an AlGaN active layer, an Zn-doped AlGaN cladding layer, and a Zn-doped GaN capping layer. All of the epitaxial layers of LED structure were grown consecutively with a multi-sliding boat system. Room-temperature electroluminescence (EL) characteristics show an emission peak wavelength of 330 nm at room temperature. The aging test result of SAG-UV LED shows that the current was changed from 27.7 to 31.2 mA during 170 h at room temperature. At the current-voltage (I-V) measurement, the turn-on voltage of the SAG-UV LED is 3.5 V at room temperature. The value of the series resistance is about 200 ?. We find that the mixed-source HVPE method with multi-sliding boat system is possible to be one of the growth methods of ultra-violet LEDs with high quality epi-layer.

Jeon, Hunsoo; Lee, Gang Seok; Jung, Se-Gyo; Bae, Seon Min; Shin, Min Jeong; Kim, Kyoung Hwa; Yang, Min; Yi, Sam Nyung; Ahn, Hyung Soo; Yu, Young-Moon; Huh, Yoon; Kim, Suck-Whan; Ha, Hong-Ju; Sawaki, Nobuhiko

2012-01-01

236

Nucleus and spiral growth mechanisms of nitride semiconductors in metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Nucleus and spiral growth mechanisms of GaN and InN are investigated using the selective-area metalorganic vapor phase epitaxy (SA-MOVPE) technique on GaN bulk substrates. Nucleus growth of GaN occurs within selective areas having no screw-type dislocations, while spiral growth occurs within selective areas having screw-type dislocations. These growth modes are simultaneously observed on a single substrate in a single growth run. The nucleus and spiral growths of GaN result in the formation of step-free surfaces and growth spirals, respectively, wherein the interstep distance of growth spirals enables us to estimate the degree of surface supersaturation (?). The ? dependences of nucleus and spiral growth rates of GaN are experimentally investigated. We found that these dependences are well explained by the classical crystal growth theories advocated by Burton, Cabrera, and Frank. We also investigate nucleation of InN using step-free GaN surfaces as an ideal platform.

Akasaka, Tetsuya; Yamamoto, Hideki

2014-10-01

237

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

238

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

239

Pentacene/K12 solar cells formed by organic vapor phase deposition  

NASA Astrophysics Data System (ADS)

This study reports on an organic solar cell structure utilizing K12 as a new low-temperature processable small-molecule acceptor material. Pentacene (PEN) and K12 were deposited onto indium tin oxide by means of organic vapor phase deposition (OVPD) as bilayer solar cells. The resulting solar cell was characterized electrically by current density-voltage (J-V) measurements and optically by photocurrent and reflectivity measurements. The J-V characteristic under AM 1.5 illumination indicates a short-circuit current of 0.45 mA/cm2 (Jsc), a fill factor of 38% (FF), and an open-circuit (Voc) voltage of 0.71 V. Current generation is found to predominantly occur in the K12 layer, although strong light absorption in the PEN layer is detected. We suggest that either a dipole shift between the layers or the fission of singlet excitons in the PEN layer leads to this observation. Although the efficiency of the device is low in combination with PEN, our experiment successfully demonstrates the use of K12 as a low-temperature acceptor material in OVPD processes.

Axmann, Sebastian; Brast, Michael; Pandey, Ajay Kumar; Burn, Paul; Meredith, Paul; Heuken, Michael; Vescan, Andrei; Kalisch, Holger

2014-01-01

240

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

241

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

SciTech Connect

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 10{sup 18}–10{sup 20}?cm{sup ?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?cm{sup 2}?V{sup ?1}?s{sup ?1} at n?=?3.7?×?10{sup 18}?cm{sup ?3}.

Oshima, Yuichi, E-mail: OSHIMA.Yuichi@nims.go.jp; Víllora, Encarnación G.; Shimamura, Kiyoshi [Environment and Energy Materials Research Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan)

2014-04-21

242

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

243

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

244

Field tests of a chemiresistor sensor for in-situ monitoring of vapor-phase contaminants  

NASA Astrophysics Data System (ADS)

An in-situ chemiresistor sensor has been developed that can detect volatile organic compounds in subsurface environmental applications. Several field tests were conducted in 2001 and 2002 to test the reliability, operation, and performance of the in-situ chemiresistor sensor system. The chemiresistor consists of a carbon-loaded polymer deposited onto a microfabricated circuit. The polymer swells reversibly in the presence of volatile organic compounds as vapor-phase molecules absorb into the polymer, causing a change in the electrical resistance of the circuit. The change in resistance can be calibrated to known concentrations of analytes, and arrays of chemiresistors can be used on a single chip to aid in discrimination. A waterproof housing was constructed to allow the chemiresistor to be used in a variety of media including air, soil, and water. The integrated unit, which can be buried in soils or emplaced in wells, is connected via cable to a surface-based solar-powered data logger. A cell-phone modem is used to automatically download the data from the data logger on a periodic basis. The field tests were performed at three locations: (1) Edwards Air Force Base, CA; (2) Nevada Test Site; and (3) Sandia's Chemical Waste Landfill near Albuquerque, NM. The objectives of the tests were to evaluate the ruggedness, longevity, operation, performance, and engineering requirements of these sensors in actual field settings. Results showed that the sensors could be operated continuously for long periods of time (greater than a year) using remote solar-powered data-logging stations with wireless telemetry. The sensor housing, which was constructed of 304 stainless steel, showed some signs of corrosion when placed in contaminated water for several months, but the overall integrity was maintained. The detection limits of the chemiresistors were generally found to be near 0.1% of the saturated vapor pressure of the target analyte in controlled laboratory conditions (e.g., ~100 ppmv for TCE), but fluctuations in environmental parameters and other interferences increased the detection limit by about an order of magnitude in the field tests. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.

Ho, C.; McGrath, L.; Wright, J.

2003-04-01

245

Toxicological assessment of kretek cigarettes: Part 2: Kretek and American-blended cigarettes, smoke chemistry and in vitro toxicity.  

PubMed

Two commercial kretek cigarettes typical for the Indonesian market and a reference kretek cigarette were compared to the American-blended reference cigarette 2R4F by smoke chemistry characterization and in vitro cytotoxicity and mutagenicity assessments. Despite the widely diverse designs and deliveries of the selected kretek cigarettes, their smoke composition and in vitro toxicity data present a consistent pattern when data were normalized to total particulate matter (TPM) deliveries. This confirms the applicability of the studies' conclusions to a wide range of kretek cigarette products. After normalization to TPM delivery, nicotine smoke yields of kretek cigarettes were 29-46% lower than that of the 2R4F. The yields of other nitrogenous compounds were also much lower, less than would be expected from the mere substitution of one third of the tobacco filler by clove material. Yields of light molecular weight pyrolytic compounds, notably aldehydes and hydrocarbons, were reduced, while yields of polycyclic aromatic hydrocarbons were unchanged and phenol yield was increased. The normalized in vitro toxicity was lowered accordingly, reflecting the yield reductions in gas-phase cytotoxic compounds and some particulate-phase mutagenic compounds. These results do not support a higher toxicity of the smoke of kretek cigarettes compared to American-blended cigarettes. PMID:25497993

Piadé, J-J; Roemer, E; Dempsey, R; Hornig, G; Deger Evans, A; Völkel, H; Schramke, H; Trelles-Sticken, E; Wittke, S; Weber, S; Schorp, M K

2014-12-01

246

Chemical analysis of cigarette smoke particulate generated in the MSB-01 in vitro whole smoke exposure system.  

PubMed

Cigarette mainstream smoke (MS) is a dynamic aerosol consisting of a gas-vapor phase and a particulate phase. In recent years, novel in vitro whole smoke exposure systems have been developed to expose cells directly to whole MS. One such system is the Burghart Mimic Smoker-01 (MSB-01). Our previous data using the MSB-01 indicated that a 50 +/- 10% loss of particulate matter occurred prior to MS delivery into the exposure chamber. Additionally, a change in aerosol particle diameter was also measured, suggesting that the chemical composition of MS might be changing within the system. In this study, we have expanded on our previous work and compared the particulate phase chemical composition of undiluted and diluted MS generated by the instrument and that of the MS delivered into the exposure chamber. The average percent delivery of cigarette smoke condensate (CSC) detected for all the measured chemical constituents was 35 +/- 13% for undiluted MS and 23 +/- 8% for 1:1 diluted MS. The data also indicate that under our experimental conditions, incomplete mixing of the freshly generated MS occurs during its dilution by the system. Taken together, the data presented here show that significant chemical changes occur between the generation of MS by the system and its delivery into the exposure chamber. This indicates that due to the dynamic nature of cigarette smoke, it is important to characterize the exposure conditions in order to gain the best insight and accurately correlate exposure with biological endpoints. PMID:19772483

Scian, Mariano J; Oldham, Michael J; Miller, John H; Kane, David B; Edmiston, Jeffery S; McKinney, Willie J

2009-10-01

247

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

248

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

249

Synthesis, optical, and magnetic properties of diluted magnetic semiconductor Zn1-xMnxO nanowires via vapor phase growth  

Microsoft Academic Search

Diluted magnetic semiconductor Zn1-xMnxO nanowires were synthesized via an in situ doping of manganese in ZnO nanowires using vapor phase growth at 500 °C. The maximum content of the manganese in the ZnO is around 13 at. %, approaching the maximum thermal equilibrium limit of Mn solubility in ZnO at the growth temperature. Structure and composition analysis revealed that the

Y. Q. Chang; D. B. Wang; X. H. Luo; X. Y. Xu; X. H. Chen; L. Li; C. P. Chen; R. M. Wang; J. Xu; D. P. Yu

2003-01-01

250

Synthesis, optical, and magnetic properties of diluted magnetic semiconductor Zn1?xMnxO nanowires via vapor phase growth  

Microsoft Academic Search

Diluted magnetic semiconductor Zn1?xMnxO nanowires were synthesized via an in situ doping of manganese in ZnO nanowires using vapor phase growth at 500 °C. The maximum content of the manganese in the ZnO is around 13 at. %, approaching the maximum thermal equilibrium limit of Mn solubility in ZnO at the growth temperature. Structure and composition analysis revealed that the

Y. Q. Chang; D. B. Wang; X. H. Luo; X. Y. Xu; X. H. Chen; L. Li; C. P. Chen; R. M. Wang; J. Xu; D. P. Yu

2003-01-01

251

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

252

Impact of nitrogen incorporation on pseudomorphic site-controlled quantum dots grown by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

We report on some surprising optical properties of diluted nitride InGaAs1-?N?/GaAs (? ?1) pyramidal site-controlled quantum dots, grown by metalorganic vapor phase epitaxy on patterned GaAs (111)B substrates. Microphotoluminescence characterizations showed antibinding exciton/biexciton behavior, a spread of exciton lifetimes in an otherwise very uniform sample, with unexpected long neutral exciton lifetimes (up to 7 ns) and a nearly zero fine structure splitting on a majority of dots.

Dimastrodonato, V.; Mereni, L. O.; Juska, G.; Pelucchi, E.

2010-08-01

253

High external efficiency (36 percent) 5-micron mesa isolated GaAs quantum well laser by organometallic vapor phase epitaxy  

Microsoft Academic Search

High external power efficiencies of 36 percent are obtained from 5-micron mesa isolated graded-index separate-confinement heterostructure single quantum well lasers grown by organometallic vapor phase epitaxy. Threshold currents of 21 mA are reported for a 5 x 96 micron cavity laser with differential quantum efficiencies of as high as 80 percent at 6 mW\\/facet. In addition, high facet power densities

D. F. Welch; C. F. Schaus; J. R. Shealy

1985-01-01

254

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

255

p-type doping with N and Li acceptors of ZnS grown by metalorganic vapor phase epitaxy  

Microsoft Academic Search

ZnS layers were grown by metalorganic vapor phase epitaxy on GaAs substrates using diethylzinc, ditertiarybutyl sulphide, and triallylamine as organometallic sources. After postgrowth rapid thermal annealing, the ZnS layers showed p-type conductivity with hole concentrations up to 1018 cm-3. Photoluminescence measurements gave additional indications of the presence of electrically active nitrogen acceptors. In separate experiments, lithium was diffused from a

L. Svob; C. Thiandoume; A. Lusson; M. Bouanani; Y. Marfaing; O. Gorochov

2000-01-01

256

A study of spatial water vapor distributions by using one-way residuals of GPS phase measurements  

NASA Astrophysics Data System (ADS)

We investigated water vapor distribution in the troposphere, concentrating especially on meso-scale phenomena, such as a cumulus cloud, with dimension less than about 10 km in the horizontal direction by using GPS phase signals along their propagation paths. Slant path water vapor can be estimated from the GPS phase residuals obtained by subtracting the theoretical phase value from the observed one. We obtained the residuals as by-products of phase data analysis with the GIPSY-OASIS II software. We analyzed a 11-day campaign data set obtained at Yamagawa (31.2°N, 130.6°E), Japan in June, 1996. During the observation, four sudden weather condition changes were seen, the passage of a cold front and Baiu fronts. The fluctuation of the residuals is dominated by their dependence on elevation angles of the GPS Satellites rather than the fine variation of water vapor. Thus, we corrected the residuals by subtracting the elevation-angle-dependence, which was obtained by means of the residuals, for each elevation angle over the entire observation period. The water vapor distribution calculated from the corrected residuals showed more realistic features that correspond to frontal structures. However, this correlation occurred only in several cases of changes of weather condition with the passage of fronts. We further obtained good consistency with the corrected residuals even among the different types of antennas which were located within a few meters by using the another data-sets of past campaigns which were carried out on the campus of Nagoya Univ. (35.2°N, 137.0°E), Japan in October.

Yoshihara, T.; Tsuda, T.; Hirahara, K.

2001-05-01

257

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

258

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...

259

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...

260

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 ...

261

Improved aging performance of vapor phase deposited hydrophobic self-assembled monolayers  

NASA Astrophysics Data System (ADS)

A hydrophobic self-assembled monolayer (SAM) of fluoro-octyl-trichloro-silane (FOTS) was deposited on silicon using a vapor phase technique. The aging of the hydrophobic layer was examined using water contact angle measurements. It has been found that while such monolayer films suffer from a loss of hydrophobicity with time, pre-immersion nitrogen annealing can significantly improve the aging characteristics of these monolayers. The effect of nitrogen annealing on the improved aging properties of SAM coatings has been investigated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The hydrolytic stability and the effect of nitrogen annealing were studied by morphological evolution during immersion. A spontaneous formation of silane mounds on the surface of the monolayers was found by AFM. These mounds have been irreversibly transformed from initially uniform hydrophobic surface layers. It is highly probable that the compliance of these mounds can reasonably allow hydrophilic sites to be located around the mounds. Interestingly, the density of these mounds formation is very less on the annealed samples. XPS reveals a higher level of coverage by the N2-annealed film due to agglomeration. A relative abundance of CF3 and CF2 moieties in the annealed film may explain the enhancement of the hydrophobicity as revealed by higher level of water contact angle. This hydrophobicity was found to be significantly stable in water. This novel finding explains the improved hydrophobic stability of FOTS monolayers as primarily a morpho-chemical effect that originates from the densification of the monolayers upon annealing.

Gnanappa, Arun Kumar; O'Murchu, Cian; Slattery, Orla; Peters, Frank; O'Hara, Tony; Aszalós-Kiss, Balázs; Tofail, Syed A. M.

2011-02-01

262

Matrix Isolation Studies of Carbonic Acid—The Vapor Phase above the ?-Polymorph  

PubMed Central

Twenty years ago two different polymorphs of carbonic acid, ?- and ?-H2CO3, were isolated as thin, crystalline films. They were characterized by infrared and, of late, by Raman spectroscopy. Determination of the crystal structure of these two polymorphs, using cryopowder and thin film X-ray diffraction techniques, has failed so far. Recently, we succeeded in sublimating ?-H2CO3 and trapping the vapor phase in a noble gas matrix, which was analyzed by infrared spectroscopy. In the same way we have now investigated the ?-polymorph. Unlike ?-H2CO3, ?-H2CO3 was regarded to decompose upon sublimation. Still, we have succeeded in isolation of undecomposed carbonic acid in the matrix and recondensation after removal of the matrix here. This possibility of sublimation and recondensation cycles of ?-H2CO3 adds a new aspect to the chemistry of carbonic acid in astrophysical environments, especially because there is a direct way of ?-H2CO3 formation in space, but none for ?-H2CO3. Assignments of the FTIR spectra of the isolated molecules unambiguously reveal two different carbonic acid monomer conformers (C2v and Cs). In contrast to the earlier study on ?-H2CO3, we do not find evidence for centrosymmetric (C2h) carbonic acid dimers here. This suggests that two monomers are entropically favored at the sublimation temperature of 250 K for ?-H2CO3, whereas they are not at the sublimation temperature of 210 K for ?-H2CO3. PMID:23631554

2013-01-01

263

Aluminum Nitride Micro-Channels Grown via Metal Organic Vapor Phase Epitaxy for MEMs Applications  

SciTech Connect

Aluminum nitride (AlN) is a promising material for a number of applications due to its temperature and chemical stability. Furthermore, AlN maintains its piezoelectric properties at higher temperatures than more commonly used materials, such as Lead Zirconate Titanate (PZT) [1, 2], making AlN attractive for high temperature micro and nanoelectromechanical (MEMs and NEMs) applications including, but not limited to, high temperature sensors and actuators, micro-channels for fuel cell applications, and micromechanical resonators. This work presents a novel AlN micro-channel fabrication technique using Metal Organic Vapor Phase Epitaxy (MOVPE). AlN easily nucleates on dielectric surfaces due to the large sticking coefficient and short diffusion length of the aluminum species resulting in a high quality polycrystalline growth on typical mask materials, such as silicon dioxide and silicon nitride [3,4]. The fabrication process introduced involves partially masking a substrate with a silicon dioxide striped pattern and then growing AlN via MOVPE simultaneously on the dielectric mask and exposed substrate. A buffered oxide etch is then used to remove the underlying silicon dioxide and leave a free standing AlN micro-channel. The width of the channel has been varied from 5 ìm to 110 ìm and the height of the air gap from 130 nm to 800 nm indicating the stability of the structure. Furthermore, this versatile process has been performed on (111) silicon, c-plane sapphire, and gallium nitride epilayers on sapphire substrates. Reflection High Energy Electron Diffraction (RHEED), Atomic Force Microscopy (AFM), and Raman measurements have been taken on channels grown on each substrate and indicate that the substrate is influencing the growth of the AlN micro-channels on the SiO2 sacrificial layer.

Rodak, L.E.; Kuchibhatla, S.; Famouri, P.; Ting, L.; Korakakis, D.

2008-01-01

264

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

265

Recent progress in GaInAsSb thermophotovoltaics grown by organometallic vapor phase epitaxy  

SciTech Connect

Studies on the materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for thermophotovoltaic (TPV) devices are reviewed. Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} epilayers were grown lattice matched to GaSb substrates by organometallic vapor phase epitaxy (OMVPE) using all organometallic precursors including triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony with diethyltellurium and dimethylzinc as the n- and p-type dopants, respectively. The overall material quality of these alloys depends on growth temperature, In content, V/III ratio, substrate misorientation, and to a lesser extent, growth rate. A mirror-like surface morphology and room temperature photoluminescence (PL) are obtained for GaInAsSb layers with peak emission in the wavelength range between 2 and 2.5 {micro}m. The crystal quality improves for growth temperature decreasing from 575 to 525 C, and with decreasing In content, as based on epilayer surface morphology and low temperature PL spectra. A trend of smaller full width at half-maximum for low temperature PL spectra is observed as the growth rate is increased from 1.5 to 2.5 and 5 {micro}m/h. In general, GaInAsSb layers grown on (100) GaSb substrates with a 6{degree} toward (111)B misorientation exhibited overall better material quality than layers grown on the more standard substrate (100)2{degree} toward (110). Consistent growth of high performance lattice-matched GaInAsSb TPV devices is also demonstrated.

Wang, C.A.; Choi, H.K.; Oakley, D.C. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

1998-06-01

266

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

267

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

268

The role of polymer formation during vapor phase lubrication of silicon.  

SciTech Connect

The lubrication of silicon surfaces with alcohol vapors has recently been demonstrated. With a sufficient concentration of pentanol vapor present, sliding of a silica ball on an oxidized silicon wafer can proceed with no measurable wear. The initial results of time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of wear surfaces revealed a reaction product having thickness on the order of a monolayer, and with an ion spectrum that included fragments having molecular weights of 200 or more that occurred only inside the wear tracks. The parent alcohol molecule pentanol, has molecular weight of 88amu, suggesting that reactions of adsorbed alcohols on the wearing surfaces allowed polymerization of the alcohols to form higher molecular weight species. In addition to pin-on-disk studies, lubrication of silicon surfaces with pentanol vapors has also been demonstrated using MicroElectroMechanical Systems (MEMS) devices. Recent investigations of the reaction mechanisms of the alcohol molecules with the oxidized silicon surfaces have shown that wearless sliding requires a concentration of the alcohol vapor that is dependent upon the contact stress during sliding, with higher stress requiring a greater concentration of alcohol. Different vapor precursors including those with acid functionality, olefins, and methyl termination also produce polymeric reaction products, and can lubricate the silica surfaces. Doping the operating environment with oxygen was found to quench the formation of the polymeric reaction product, and demonstrates that polymer formation is not necessary for wearless sliding.

Dugger, Michael Thomas; Dirk, Shawn M.; Ohlhausen, James Anthony

2010-10-01

269

Homogeneous vapor phase nucleation of a large fatty acid: Stearic acid  

NASA Astrophysics Data System (ADS)

Homogeneous nucleation measurements are made on stearic acid vapor using a diffusion cloud chamber and the resulting critical supersaturations compared with the predictions of the classical Becker-Doering theory. These measurements are difficult because of the unusually low pressures and high temperatures required to investigate the involatile stearic acid molecule. The results indicate a definite discrepancy between theory and experiment. Measured critical supersaturations lie 27% above the theory at the lowest temperature and 10% below the theory at the highest temperature. Calculations show that part of this increase in experimental critical supersaturation at the lower temperatures could be due to association in the vapor. There are two additional findings: (1) The usual top plate boundary condition must be corrected for molecules, such as stearic acid, which have low equilibrium vapor pressures in the temperature range of interest. (2) The growth times for stearic acid droplets are at the limits that can be tolerated in a feasible diffusion cloud chamber experiment. This study suggests an area for future investigation. Once the association equilibrium constant for stearic acid vapor is known, the data presented here can be reanalyzed and the extent to which the dimer stabilizes the supersaturated vapor determined.

Becker, Carol

1980-04-01

270

Integrated natural-gas-engine cooling jacket vapor-compressor program. Annual progress report (phase 2), January-December 1987  

SciTech Connect

A unique, alternative cogeneration system was designed that will provide an industrial or commercial energy user with high-pressure steam and electricity directly from a packaged cogeneration system. The Integrated Gas Engine Vapor Compression System concept includes an engine-generator set and a steam screw compressor that are mechanically integrated with the engine. The gas-fueled engine is ebulliently cooled, thus allowing its water jacket heat to be recovered in the form of low-pressure steam. This steam is then compressed by the steam compressor to a higher pressure, and when combined with the high-pressure steam generated in the engine's exhaust gas boiler it provides the end user with a more useable thermal energy source. Phase 1B of this project was completed in 1986 and consisted primarily of the procurement of equipment and the final design and assembly of a prototype integrated gas-engine vapor-compression system.

DiBella, F.A.; Becker, F.

1988-01-01

271

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

272

Columnar jointing in vapor-phase-altered, non-welded Cerro Gal??n Ignimbrite, Paycuqui, Argentina  

USGS Publications Warehouse

Columnar jointing is thought to occur primarily in lavas and welded pyroclastic flow deposits. However, the non-welded Cerro Gal??n Ignimbrite at Paycuqui, Argentina, contains well-developed columnar joints that are instead due to high-temperature vapor-phase alteration of the deposit, where devitrification and vapor-phase crystallization have increased the density and cohesion of the upper half of the section. Thermal remanent magnetization analyses of entrained lithic clasts indicate high emplacement temperatures, above 630??C, but the lack of welding textures indicates temperatures below the glass transition temperature. In order to remain below the glass transition at 630??C, the minimum cooling rate prior to deposition was 3.0 ?? 10-3-8.5 ?? 10-2??C/min (depending on the experimental data used for comparison). Alternatively, if the deposit was emplaced above the glass transition temperature, conductive cooling alone was insufficient to prevent welding. Crack patterns (average, 4.5 sides to each polygon) and column diameters (average, 75 cm) are consistent with relatively rapid cooling, where advective heat loss due to vapor fluxing increases cooling over simple conductive heat transfer. The presence of regularly spaced, complex radiating joint patterns is consistent with fumarolic gas rise, where volatiles originated in the valley-confined drainage system below. Joint spacing is a proxy for cooling rates and is controlled by depositional thickness/valley width. We suggest that the formation of joints in high-temperature, non-welded deposits is aided by the presence of underlying external water, where vapor transfer causes crystallization in pore spaces, densifies the deposit, and helps prevent welding. ?? 2011 Springer-Verlag.

Wright, H.M.N.; Lesti, C.; Cas, R.A.F.; Porreca, M.; Viramonte, J.G.; Folkes, C.B.; Giordano, G.

2011-01-01

273

TREATMENT OF PRODUCED WATERS USING A SURFACTANT MODIFIED ZEOLITE/VAPOR PHASE BIOREATOR SYSTEM  

SciTech Connect

Co-produced water from the oil and gas industry 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. An efficient, cost-effective treatment technology is needed to remove these constituents. 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 March 2003 through September 2003. We have continued our investigation of SMZ regeneration from our previous DOE project. Ten saturation/stripping cycles have been completed for SMZ columns saturated with BTEX compounds. The results suggest that BTEX sorption capacity is not lost after ten saturation/regeneration cycles. The composition of produced water from a site operated by Crystal Solutions Ltd. in Wyoming has been characterized and was used to identify key semi-volatile components. Isotherms with selected semi-volatile components have been initiated and preliminary results have been obtained. The experimental vapor phase bioreactors for this project have been designed and assembled to treat the off-gas from the SMZ regeneration process. These columns will be used both in the laboratory and in the proposed field testing to be conducted next year. Innocula for the columns that degrade all of the BTEX columns have been developed.

LYNN E. KATZ; KERRY A. KINNEY; R.S. BOWMAN; E.J. SULLIVAN

2003-10-01

274

Theoretical approaches and experimental evidence for liquid-vapor phase transitions in nuclei  

SciTech Connect

The leptodermous approximation is applied to nuclear systems for T > 0. The introduction of surface corrections leads to anomalous caloric curves and to negative heat capacities in the liquid-gas coexistence region. Clusterization in the vapor is described by associating surface energy to clusters according to Fisher's formula. The three-dimensional Ising model, a leptodermous system par excellence, does obey rigorously Fisher's scaling up to the critical point. Multifragmentation data from several experiments including the ISiS and EOS Collaborations, as well as compound nucleus fragment emission at much lower energy follow the same scaling, thus providing the strongest evidence yet of liquid-vapor coexistence.

Moretto, L.G.; Elliott, J.B.; Phair, L.; Wozniak, G.J.; Mader, C.M.; Chappars, A.

2001-01-01

275

[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 pleasant throat hit to the smoker in the first 6 seconds 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

276

Advertising media and cigarette demand.  

PubMed

Using state-level panel data for the USA spanning three decades, this research estimates the demand for cigarettes. The main contribution lies in studying the effects of cigarette advertising disaggregated across five qualitatively different groups. Results show cigarette demand to be near unit elastic, the income effects to be generally insignificant and border price effects and habit effects to be significant. Regarding advertising effects, aggregate cigarette advertising has a negative effect on smoking. Important differences across advertising media emerge when cigarette advertising is disaggregated. The effects of public entertainment and Internet cigarette advertising are stronger than those of other media. Anti-smoking messages accompanying print cigarette advertising seem relatively more effective. Implications for smoking control policy are discussed. PMID:22167909

Goel, Rajeev K

2011-01-01

277

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

278

Development of vapor phase hydrogen peroxide sterilization process for spacecraft applications  

NASA Technical Reports Server (NTRS)

This paper will present test data and discussion on the work we are conducting at JPL to address the following issues: 1) efficacy of sterilization process; 2) diffusion of hydrogen peroxide under sterilization process conditions into hard to reach places; 3) materials and components compatibility with the sterilization process and 4) development of methodology to protect sensitive components from hydrogen peroxide vapor.

Rohatgi, N.; Schubert, W.; Knight, J.; Quigley, M.; Forsberg, G.; Ganapathi, G.; Yarbrough, C.; Koukol, R.

2001-01-01

279

Physics-based agent to simulant correlations for vapor phase mass transport.  

PubMed

Chemical warfare agent simulants are often used as an agent surrogate to perform environmental testing, mitigating exposure hazards. This work specifically addresses the assessment of downwind agent vapor concentration resulting from an evaporating simulant droplet. A previously developed methodology was used to estimate the mass diffusivities of the chemical warfare agent simulants methyl salicylate, 2-chloroethyl ethyl sulfide, di-ethyl malonate, and chloroethyl phenyl sulfide. Along with the diffusivity of the chemical warfare agent bis(2-chloroethyl) sulfide, the simulant diffusivities were used in an advection-diffusion model to predict the vapor concentrations downwind from an evaporating droplet of each chemical at various wind velocities and temperatures. The results demonstrate that the simulant-to-agent concentration ratio and the corresponding vapor pressure ratio are equivalent under certain conditions. Specifically, the relationship is valid within ranges of measurement locations relative to the evaporating droplet and observation times. The valid ranges depend on the relative transport properties of the agent and simulant, and whether vapor transport is diffusion or advection dominant. PMID:24225584

Willis, Matthew P; Varady, Mark J; Pearl, Thomas P; Fouse, Janet C; Riley, Patrick C; Mantooth, Brent A; Lalain, Teri A

2013-12-15

280

Experimental identification of evaporator dynamics for vapor compression refrigeration cycle during phase transition  

Microsoft Academic Search

Experimental identification of the evaporator dynamics in a vapor compression cycle (VCC) subjected to imposed heat flux in the evaporator is studied. The imposed heat flux boundary condition represents a specific application of the VCC for electronics cooling. However, this application requires different models and control algorithms than traditional VCCs with fluid-to-fluid heat exchanges because of the faster time response

Juan E. Catano; TieJun Zhang; Yoav Peles; Michael K. Jensen; John T. Wen

2010-01-01

281

Dry release for surface micromachining with HF vapor-phase etching  

Microsoft Academic Search

A new method for dry etching of silicon dioxide for surface micromachining is presented to obtain very compliant polysilicon microstructures with negligible stiction problem and to greatly simplify the overall releasing procedure as well. By etching the sacrificial silicon dioxide with hydrofluoric acid (HF) vapor instead of conventional aqueous HF solution, the need for subsequent rinsing and an elaborate drying

Yong-Il Lee; K.-H. Park; J. Lee; C.-S. Lee; H. J. Yoo; C.-J. Kim; Y.-S. Yoon

1997-01-01

282

Substrate-Induced Phase of a [1]Benzothieno[3,2-b]benzothiophene Derivative and Phase Evolution by Aging and Solvent Vapor Annealing.  

PubMed

Substrate-induced phases (SIPs) are polymorphic phases that are found in thin films of a material and are different from the single crystal or "bulk" structure of a material. In this work, we investigate the presence of a SIP in the family of [1]benzothieno[3,2-b]benzothiophene (BTBT) organic semiconductors and the effect of aging and solvent vapor annealing on the film structure. Through extensive X-ray structural investigations of spin coated films, we find a SIP with a significantly different structure to that found in single crystals of the same material forms; the SIP has a herringbone motif while single crystals display layered ?-? stacking. Over time, the structure of the film is found to slowly convert to the single crystal structure. Solvent vapor annealing initiates the same structural evolution process but at a greatly increased rate, and near complete conversion can be achieved in a short period of time. As properties such as charge transport capability are determined by the molecular structure, this work highlights the importance of understanding and controlling the structure of organic semiconductor films and presents a simple method to control the film structure by solvent vapor annealing. PMID:25569633

Jones, Andrew O F; Geerts, Yves H; Karpinska, Jolanta; Kennedy, Alan R; Resel, Roland; Röthel, Christian; Ruzié, Christian; Werzer, Oliver; Sferrazza, Michele

2015-01-28

283

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

284

3D analysis of vapor-liquid two phase flow based on compressible two fluid-one pressure model  

SciTech Connect

General problems were investigated relating to the numerical methodologies in simulating a vapor-liquid two phase flow field based on the two fluid-one pressure model. Major difficulties are caused by the wide time constant range of dominant processes included in the phenomenon. This numerical stiffness problem was solved by applying the implicit method for the interfacial interaction and density wave propagation processes. Fluid state variables were derived by Newton-Raphson iteration method after solving the pressure equation. Several pressure iteration schemes were compared their performance in combination with the outer Newton-Raphson loop. Among them, it was found that the MILUCR scheme is most effective. The isolated cylinder sample calculation indicates that the void localization is mainly caused by the vapor mobility. The k-e model was applied to simulate turbulent effects, which enhanced the above-mentioned trend. The detailed BWR spacer samples indicate that the vapor acceleration and its winding motion is notable in the complex structures.

Hotta, A. [Toden Software, Inc., Minato-ku, Tokyo (Japan)

1995-12-31

285

Characterization of particulate and vapor phase polycyclic aromatic hydrocarbons in indoor and outdoor air of primary schools  

NASA Astrophysics Data System (ADS)

The indoor air of schools is considered as one of the most important factors affecting the health of children. The aim of the presented research was to characterize polycyclic aromatic hydrocarbons (PAHs) in indoor and outdoor air of schools. The sampling campaign was conducted during the heating season of 2011/2012. Five primary schools from various urban settings in the city of Kaunas, Lithuania. 150 daily samples of particulate and vapor phases were collected during the sampling period. The ultrasonic extractions followed by the gas chromatography and mass spectroscopy (GS/MS) analyses were used for the determination of PAHs. The concentration of total PAHs in the PM2.5 fraction ranged from 20.3 to 131.1 ng m-3, while total suspended particles (TSP) fraction contained from 19.9 to 80.3 ng m-3 of total PAHs. The vapor phase concentration of PAHs ranged from 67.2 to 372.5 ng m-3. The most abundant PAH in both phases was naphthalene. In order to define sources of indoor and outdoor PAHs several source apportionment methods were applied. The analysis revealed that emissions from motor vehicles and fuel burning for heating purposes were the major sources of PAHs in the city of Kaunas.

Krugly, Edvinas; Martuzevicius, Dainius; Sidaraviciute, Ruta; Ciuzas, Darius; Prasauskas, Tadas; Kauneliene, Violeta; Stasiulaitiene, Inga; Kliucininkas, Linas

2014-01-01

286

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. PMID:23176442

2012-01-01

287

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

288

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

2014-06-21

289

Vapor phase synthesis and characterization of bimetallic alloy and supported nanoparticle catalysts  

Microsoft Academic Search

The laser vaporization controlled condensation (LVCC) technique coupled with a differential mobility analyzer (DMA) is used to synthesize size-selected alloy nanoparticles and nanoparticle catalyst systems. The formation of Au–Ag alloy nanoparticles is concluded from the observation of only one plasmon band. The maximum of the plasmon absorption is found to vary linearly with the gold mole fraction. For the Au–Pd

V. Abdelsayed; K. M. Saoud; M. Samy El-Shall

2006-01-01

290

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

291

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

292

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

293

Molecularly imprinted polymer sensors for detection in the gas, liquid, and vapor phase.  

PubMed

Fast, reliable, and inexpensive analytical techniques for detection of airborne chemical warfare agents are desperately needed. Recent advances in the field of molecularly imprinted polymers have created synthetic nanomaterials that can sensitively and selectively detect these materials in aqueous environments, but thus far, they have not been demonstrated to work for detection of vapors. The imprinted polymers function by mimicking the function of biological receptors. They can provide high sensitivity and selectivity but, unlike their biological counterparts, maintain excellent thermal and mechanical stability. The traditional imprinted polymer approach is further enhanced in this work by the addition of a luminescent europium that has been introduced into the polymers to provide enhanced chemical affinity as well as a method for signal transduction to indicate the binding event. The europium in these polymers is so sensitive to the bound target; it can distinguish between species differing by a single methyl group. The imprinted polymer technology is fiber optic-based making it inexpensive and easily integratable with commercially available miniature fiber optic spectrometer technologies to provide a shoebox size device. In this work, we will describe efforts to apply these sensors for detection of airborne materials and vapors. Successful application of this technology will provide accurate low level vapor detection of chemical agents or pesticides with little to no false positives. PMID:22641530

Jenkins, Amanda L; Ellzy, Michael W; Buettner, Leonard C

2012-06-01

294

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

295

Synthesis of ultrafine particles of intermetallic compounds by the vapor-phase magnesium reduction of chloride mixtures: Part I. Titanium aluminides  

Microsoft Academic Search

A new chemical synthesis process for the preparation of intermetallic compounds has been developed. It involves the vapor-phase\\u000a reduction of mixtures of constituent metal chlorides by magnesium vapor to produce intermetallic compounds in the form of\\u000a fine powder. The advantages of the process include (a) the use of inexpensive raw materials, (b) low reaction temperatures,\\u000a and (c) products in the

H. Y. Sohn; S. Paldey

1998-01-01

296

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

297

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. PMID:21711601

2011-01-01

298

Surface acoustic waves in semi-insulating Fe-doped GaN films grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

The propagation properties of surface acoustic waves (SAWs) in semi-insulating Fe-doped GaN films grown on sapphire substrates by hydride vapor phase epitaxy are investigated. Compared with native n-type GaN, Fe-doped GaN exhibits a higher electromechanical coupling coefficient due to its high electrical resistivity. In addition, guided longitudinal leaky surface acoustic wave (LLSAW) was observed experimentally with a very high phase velocity (about 7890 m/s), and this mode was verified by numerical simulations. The small propagation attenuation of LLSAW along liquid/solid interfaces was demonstrated in glycerol solutions, which implies the potential applications in high-frequency chemical sensing.

Fan, Yingmin; Liu, Zhenghui; Xu, Gengzhao; Zhong, Haijian; Huang, Zengli; Zhang, Yumin; Wang, Jianfeng; Xu, Ke

2014-08-01

299

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

300

Condensation of nonequilibrium phases of refractory silicates from the vapor. [interstellar particle formation  

NASA Technical Reports Server (NTRS)

Silicon monoxide solid was evaporated in a bell jar containing reducing, neutral, or oxidizing atmospheres at pressures of a few torr. The vapor invariably condensed as smoke-sized particles of silicon sesquioxide, Si2O3. The condensation of a solid whose composition differs from that of the parent gas and is apparently the least stable of the three solid species illustrates the importance of specific nucleation effects in the condensation process. This result has significant implications for theories of formation of grains in space.

Day, K. L.; Donn, B.

1978-01-01

301

Laboratory studies of silicon vapor deposition, phase A. [feasibility of producing thin films for photovoltaic applications  

NASA Technical Reports Server (NTRS)

A system is described capable of carrying out silicon vapor deposition experiments in the low 10 to the minus 10th power torr vacuum range. The system was assembled and tested for use in a program aimed at exploration of vacuum heteroepitaxy of silicon on several substrates of potential interest for photovoltaic applications. An experiment is described in which a silicon layer 2.5 microns thick was deposited on a pyrolytically cleaned tungsten substrate held at a temperature of 400 C. Using a resistance heated silicon source, thicker layers can be deposited in periods of hours by utilizing closer source to substrate distances.

Frost, R. T.; Racette, G. W.; Stockhoff, E. H.

1977-01-01

302

Vapor-Phase-Deposited Organosilane Coatings as "Hardening" Agents for High-Peak-Power Laser Optics  

SciTech Connect

Multilayer-dielectric (MLD) diffraction gratings are used in high-power laser systems to compress laser-energy pulses. The peak power deliverable on target for these short-pulse petawatt class systems is limited by the laser-damage resistance of the optical components in the system, especially the MLD gratings. Recent experiments in our laboratory have shown that vapor treatment of MLD gratings at room temperature with organosilanes such as hexamethyldisilazane (HMDS) produces an increase in their damage threshold as compared to uncoated MLD grating control samples.

Marshall, K.L.; Culakova, Z.; Ashe, B.; Giacofei, C.; Rigatti, A.L.; Kessler, T.J.; Schmid, A.W.; Oliver, J.B.; Kozlov, A.

2008-01-07

303

On breathing in temperature in flows of a vapor due to evaporation from its spherical condensed phase  

NASA Astrophysics Data System (ADS)

One of the features in evaporation flows from a condensed phase of finite size placed in an infinite expanse of its vapor in three-dimensional space would be the existence of the so-called breathing phenomenon of temperature in its course to approach the state at infinity. The pressure of the gas, as one might expect, approaches uniformly the state specified at infinity, whereas the temperature does not but seems to take some rest for a while on its way and then starts again to approach slowly and monotonically the specified state at infinity. This is what we call breathing in temperature. This phenomenon was pointed out by Takeuchi and Onishi [Rarefied Gas Dynamics, edited by C. Shen (Pekin University Press, Beijing, 1996), pp. 887-882] in their weakly nonlinear asymptotic analysis based on the kinetic equation on steady evaporation flows from a spherical condensed phase placed in a mixture of its vapor and a noncondensable gas. The detailed discussion on this phenomenon, however, is not yet given; particularly, the reason why the temperature seems to take some rest and what originates this are not known. The present study aims to clarify the phenomenon, paying particular attention to its origin and pursuing what it is. In so doing, we have made a certain conjecture on the origin and, to show this to be true, we have taken up a simple initial and boundary-value problem of evaporation from a spherical condensed phase immersed in an infinite expanse of its vapor. Starting from a simple initial state, we followed in a numerical simulation how the flow field developed in time, getting finally a conclusion that the contact region produced initially by the evaporation process which occurs at the interface of the condensed phase is the cause; the contact region remains left undiffused at a finite distance from the interface in the flow field even at the steady state due to the counterbalance between the convection ability of the flow in the radial direction and the diffusion ability of the region itself in the opposite direction.

Onishi, Yoshimoto; Fuji, Takahiro

2008-06-01

304

Boiling liquid expanding vapor explosion: experimental research in the evolution of the two-phase flow and over-pressure.  

PubMed

In a boiling liquid expanding vapor explosion (BLEVE), the superheating and boiling of the liquefied gas inside the vessel as it fails is important information necessary to understand the mechanism of this type of disaster. In this paper, a small-scale experiment was developed to investigate the possible processes that could lead to a BLEVE. Water was used as the test fluid. High-speed video was utilized to observe the two-phase flow swelling which occurred immediately following the partial loss of containment through a simulated crack. The velocity of the two-phase swelling was measured along with pressure and temperature. It was observed that initially a mist-like two-phase layer was rapidly formed on the liquid surface (~3-4 ms) after the vessel opened. The superheated liquid rapidly boiled and this accelerated upwards the two-phase layer, the whole liquid boiled after about 17 ms form opening. It was supposed that the swelling of the two-phase layer was the possible reason for the first over-pressure measured at the top and bottom of the vessel. From 38 ms to 168 ms, the boiling of the superheated liquid weakened. And from 170 ms, the original drop/mist-like two-phase flow turned into a churn-turbulent bubbly two-phase flow, rose quickly in the field of the camera and eventually impacted the vessel top wall. The force of its impact and "cavitation" and "choke" following with the two-phase ejection were maybe main reasons for the second obvious pressure increasing. PMID:18261848

Chen, Sining; Sun, Jinhua; Wan, Wei

2008-08-15

305

A flux induced crystal phase transition in the vapor-liquid-solid growth of indium-tin oxide nanowires  

NASA Astrophysics Data System (ADS)

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.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. Electronic supplementary information (ESI) available: STEM mapping of In and Sn in an ISO nanowire (Fig. S1) and homogeneity of a fluorite ISO phase at the full length of a nanowire (Fig. S2). See DOI: 10.1039/c4nr01016g

Meng, Gang; Yanagida, Takeshi; Yoshida, Hideto; Nagashima, Kazuki; Kanai, Masaki; Zhuge, Fuwei; He, Yong; Klamchuen, Annop; Rahong, Sakon; Fang, Xiaodong; Takeda, Seiji; Kawai, Tomoji

2014-05-01

306

PATTERNS OF CIGARETTE SMOKING. PA'ITERNS OF CIGARETTE SMOKING  

E-print Network

of this century, the proportion of adult female cigarette smokers did not exceed one-quarter until the onset. Figure 2 depicts estimates of the percentage of male and female current cigarette smokers in the greater,48,67). During World War I, the War Industries Board estimated that soldiers of the Allied Armies consumed 60

Gabrieli, John

307

Vapor Phase Infrared Spectroscopy and Ab Initio Fundamental Anharmonic Frequencies of Ammonia Borane  

SciTech Connect

Infrared absorption spectra of ammonia borane vapor have been recorded between 3600 and 600 cm-1. Of the eleven infrared active modes, seven of the vibrational modes of NH3 11BH3 have been observed and four of the vibrational modes of NH3 10BH3 were observed. The spectra were recorded with sufficient resolution to observe the rotational structure of the bands, which allowed for preliminary least squares fitting of the band origins and rotational constants. First principals electronic structure calculations were performed to obtain anharmonic band origins and their intensities. The band assignments are discussed in relation to other spectroscopic techniques that have been used to study this molecule. A semi empirical estimate of the vapor pressure of ammonia borane at room temperature (22 °C) was made and found to be ~ 1 × 10-4 Torr. The assignment of the measured modes was aided by the calculated anharmonic frequencies and their infrared intensities. The combination of the CCSD(T) harmonic frequencies with the B3LYP anharmonicities, obtained from second order vibrational perturbation theory, was found to produce an overall best agreement with the measured band origins.

Sams, R. L.; Xantheas, Sotiris S.; Blake, Thomas A.

2012-03-29

308

Chemical evaluation of electronic cigarettes  

PubMed Central

Objective To review the available evidence evaluating the chemicals in refill solutions, cartridges, aerosols and environmental emissions of electronic cigarettes (e-cigarettes). Methods Systematic literature searches were conducted to identify research related to e-cigarettes and chemistry using 5 reference databases and 11 search terms. The search date range was January 2007 to September 2013. The search yielded 36 articles, of which 29 were deemed relevant for analysis. Results The levels of nicotine, tobacco-specific nitrosamines (TSNAs), aldehydes, metals, volatile organic compounds (VOCs), flavours, solvent carriers and tobacco alkaloids in e-cigarette refill solutions, cartridges, aerosols and environmental emissions vary considerably. The delivery of nicotine and the release of TSNAs, aldehydes and metals are not consistent across products. Furthermore, the nicotine level listed on the labels of e-cigarette cartridges and refill solutions is often significantly different from measured values. Phenolic compounds, polycyclic aromatic hydrocarbons and drugs have also been reported in e-cigarette refill solutions, cartridges and aerosols. Varying results in particle size distributions of particular matter emissions from e-cigarettes across studies have been observed. Methods applied for the generation and chemical analyses of aerosols differ across studies. Performance characteristics of e-cigarette devices also vary across and within brands. Conclusions Additional studies based on knowledge of e-cigarette user behaviours and scientifically validated aerosol generation and chemical analysis methods would be helpful in generating reliable measures of chemical quantities. This would allow comparisons of e-cigarette aerosol and traditional smoke constituent levels and would inform an evaluation of the toxicity potential of e-cigarettes. PMID:24732157

Cheng, Tianrong

2014-01-01

309

Effect of cigarette menthol content on mainstream smoke emissions.  

PubMed

The 2009 Family Smoking Prevention and Tobacco Control Act empowered the U.S. Food and Drug Administration to study "the impact of the use of menthol in cigarettes on the public health, including such use among children, African Americans, Hispanics and other racial and ethnic minorities," and develop recommendations. Current scientific evidence comparing human exposures between menthol and nonmenthol smokers shows mixed results. This is largely because of the many differences between commercial menthol and nonmenthol cigarettes other than their menthol content. We conducted an innovative study using two types of test cigarettes: a commercial nonmenthol brand that we mentholated at four different levels, and Camel Crush, a commercial cigarette containing a small capsule in the filter that releases menthol solution into the filter when crushed. Cigarettes were machine-smoked at each of the menthol levels investigated, and the total particulate matter (TPM) was collected on a quartz fiber filter pad and analyzed by gas chromatography/mass spectrometry for menthol, nicotine, tobacco-specific nitrosamines (TSNAs), polycyclic aromatic hydrocarbons (PAHs), cotinine, and quinoline. The mainstream smoke was also monitored continuously in real time on a puff-by-puff basis for seven gas-phase constituents (acetaldehyde, acetonitrile, acrylonitrile, benzene, 1,3-butadiene, isoprene, and 2,5-dimethylfuran), using a proton transfer reaction-mass spectrometer. Average yields (in micrograms/cigarette) for the analytes were determined. Menthol in the TPM samples increased linearly with applied menthol concentration, but the amounts of nicotine along with the target TSNAs, PAHs, cotinine, and quinoline in the cigarettes remained essentially unchanged. Similarly, yields of the targeted volatile organic compounds (VOCs) in whole smoke from the mentholated nonmenthol cigarettes that were measured in real-time were largely unaffected by their menthol levels. In the Camel Crush cigarettes, however, the VOC yields appeared to increase in the presence of menthol, especially in the gas phase. Although we succeeded in characterizing key mainstream smoke constituents in cigarettes that differ only in menthol content, further study is needed to definitively answer whether menthol affects exposure to selected cigarette constituents and thereby influences harm. PMID:21888394

Gordon, S M; Brinkman, M C; Meng, R Q; Anderson, G M; Chuang, J C; Kroeger, R R; Reyes, I L; Clark, P I

2011-10-17

310

The electronic cigarette. Official statement of the Spanish Society of Pneumology and Thoracic Surgery (SEPAR) on the efficacy, safety and regulation of electronic cigarettes.  

PubMed

The electronic cigarette (EC) is a device formed by three basic elements: battery, atomizer and cartridge. When assembled, it looks like a cigarette. The cartridge contains different substances: propylene glycol, glycerine and, sometimes, nicotine. When the user "vapes", the battery is activated, the atomizer is heated and the liquid is drawn in and vaporized. The smoker inhales the mist produced. Various substances have been detected in this mist: formaldehyde, acetaldehyde and acrolein and some heavy metals. Although these are found in lower concentrations than in cigarettes, they may still be harmful for the human body. Several surveys show that 3-10% of smokers regularly use e-cigarettes. A randomized study has shown that the efficacy of e-cigarettes for helping smokers to quit is similar to nicotine patches. Nevertheless, the study has relevant methodological limitations and reliable conclusions cannot be deduced. This report sets down the Position Statement of the Spanish Society of Pulmonology and Thoracic Surgery (SEPAR) on the efficacy and safety of e-cigarettes. This statement declares that e-cigarettes should be regulated as medicinal products. PMID:24684764

Jimenez Ruiz, Carlos A; Solano Reina, Segismundo; de Granda Orive, Jose Ignacio; Signes-Costa Minaya, Jaime; de Higes Martinez, Eva; Riesco Miranda, Juan Antonio; Altet Gómez, Neus; Lorza Blasco, Jose Javier; Barrueco Ferrero, Miguel; de Lucas Ramos, Pilar

2014-08-01

311

Comment on "Tunable generation and adsorption of energetic compounds in the vapor phase at trace levels: A tool for testing and developing sensitive and selective substrates for explosive detection"  

SciTech Connect

The evaluation of developed technologies and research on new detection approaches require the ability to generate explosive vapors in the gas phase. In this correspondence, the authors comment on a technical note describing a vaopr generator, discuss safety issues associated with explosives for vapor generators, and provide a concise review of vapor generators for explosive compounds. Approaches to measuring or monitoring the output of a vapor generators are also discussed.

Grate, Jay W.; Ewing, Robert G.; Atkinson, David A.

2013-02-13

312

Absolute integrated intensities of vapor-phase hydrogen peroxide (H202) in the mid-infrared at atmospheric pressure  

SciTech Connect

We report quantitative broadband infrared spectra of vapor-phase hydrogen peroxide (H2O2) with all spectra pressure broadened to atmospheric pressure. The spectra were generated by flowing a concentrated solution (83 weight%) of H2O2 into a gently heated disseminator and diluting with a flow of pure nitrogen carrier gas. The water vapor lines were subtracted from the resulting spectra to yield the spectrum of pure H2O2. Comparison with previous results for the ?6 band strength (including hot bands) compares favorably with the results of Klee et al. [(1999) J. Mol. Spectr. 195, 154] as well as HITRAN. The present results are 433 and 467 cm-2 atm-1 (±8% and ±3% at 298 and 323 K, respectively) for the band strength, matching well the Klee value (S = 467 cm-2 atm-1 at 296 K) for the integrated band. Other bands in the 520-7500 cm-1 interval and their potential for atmospheric monitoring are discussed.

Johnson, Timothy J.; Sams, Robert L.; Burton, Sarah D.; Blake, Thomas A.

2009-09-01

313

The Validation of Vapor Phase Hydrogen Peroxide Microbial Reduction for Planetary Protection and a Proposed Vacuum Process Specification  

NASA Technical Reports Server (NTRS)

The Jet Propulsion Laboratory, in conjunction with the NASA Planetary Protection Officer, has selected the vapor phase hydrogen peroxide sterilization process for continued development as a NASA approved sterilization technique for spacecraft subsystems and systems. The goal is to include this technique, with an appropriate specification, in NPR 8020.12C as a low temperature complementary technique to the dry heat sterilization process.To meet microbial reduction requirements for all Mars in-situ life detection and sample return missions, various planetary spacecraft subsystems will have to be exposed to a qualified sterilization process. This process could be the elevated temperature dry heat sterilization process (115 C for 40 hours) which was used to sterilize the Viking lander spacecraft. However, with utilization of such elements as highly sophisticated electronics and sensors in modern spacecraft, this process presents significant materials challenges and is thus an undesirable bioburden reduction method to design engineers. The objective of this work is to introduce vapor hydrogen peroxide (VHP) as an alternative to dry heat microbial reduction to meet planetary protection requirements.The VHP process is widely used by the medical industry to sterilize surgical instruments and biomedical devices, but high doses of VHP may degrade the performance of flight hardware, or compromise material properties. Our goal for this study was to determine the minimum VHP process conditions to achieve microbial reduction levels acceptable for planetary protection.

Chung, Shirley; Barengoltz, Jack; Kern, Roger; Koukol, Robert; Cash, Howard

2006-01-01

314

Development of a polysilicon process based on chemical vapor deposition (phase 1)  

NASA Technical Reports Server (NTRS)

A dichlorosilane-based reductive chemical vapor deposition (CVD) process demonstrated is capable of producing, at low cost, high quality polycrystalline silicon. Testing of decomposition reactor heat shields to insure that the shield provides adequate personnel protection assuming a worst case explosion was completed. Minor modifications to a production reactor heat shield provided adequate heat shield integrity. Construction of the redesigned PDU (Process Development Unit) to accommodate all safety related information proceeded on schedule. Structural steel work was completed as is the piping and instrumentation design work. Major pieces of process equipment were received and positioned in the support structure and all transfer piping and conduits to the PDU were installed. Construction was completed on a feed system for supplying DCS to an intermediate sized reactor. The feed system was successfully interfaced with a reactor equipped with a modified heat shield. Reactor checkout was completed.

Mccormick, J.; Arvidson, A.; Sawyer, D.; Plahutnik, F.

1981-01-01

315

Development of a polysilicon process based on chemical vapor deposition (phase 1)  

NASA Astrophysics Data System (ADS)

A dichlorosilane-based reductive chemical vapor deposition (CVD) process demonstrated is capable of producing, at low cost, high quality polycrystalline silicon. Testing of decomposition reactor heat shields to insure that the shield provides adequate personnel protection assuming a worst case explosion was completed. Minor modifications to a production reactor heat shield provided adequate heat shield integrity. Construction of the redesigned PDU (Process Development Unit) to accommodate all safety related information proceeded on schedule. Structural steel work was completed as is the piping and instrumentation design work. Major pieces of process equipment were received and positioned in the support structure and all transfer piping and conduits to the PDU were installed. Construction was completed on a feed system for supplying DCS to an intermediate sized reactor. The feed system was successfully interfaced with a reactor equipped with a modified heat shield. Reactor checkout was completed.

McCormick, J.; Arvidson, A.; Sawyer, D.; Plahutnik, F.

1981-06-01

316

Development of a polysilicon process based on chemical vapor deposition, phase 1  

NASA Astrophysics Data System (ADS)

The development of a dichlorosilane-based reductive chemical vapor deposition process for the production of polycrystalline silicon is discussed. Experimental data indicate that the ease of ignition and explosion severity of dichlorosilane (DCS)/air mixtures is substantially attenuated if the DCS is diluted with hydrogen. Redesign of the process development unit to accommodate safety related information is described. Several different sources of trichlorosilane were used to generate a mixture of redistributed chlorosilanes via Dowex ion exchange resin. The unseparated mixtures were then fed to an experimental reactor in which silicon was deposited and the deposited silicon analyzed for electrically active impurities. At least one trichlorosilane source provided material of requisite purity. Silicon grown in the experimental reactor was converted to single crystal material and solar cells fabricated and tested.

McCormick, J.; Sharp, K.; Arvidson, A.; Sawyer, D.

1981-03-01

317

Vacuum distillation/vapor filtration water recovery, phases 1 and 2  

NASA Technical Reports Server (NTRS)

The research is reported on the development of an evaporator for vacuum distillation/vapor filtration VD/VF water reclamation system for use on manned space flights. The design, fabrication, and tests of a six-man evaporator are described. It is concluded that: (1) A condenser with an internal rotating impeller and coolant surfaces directly opposite the condensing surfaces is an effective condenser. (2) The VD/VF evaporator, catalyst unit and condenser function satisfactorily based on thermal, mechanical and recovery performance during a 145-hour evaluation test. (3) The quality of recovered water, as measured by analyses for total organic carbon, pH, conductivity, turbidity, and viable bacteria density was within established limits for potability.

Honegger, R. J.; Remus, G. A.; Krug, E. K.

1973-01-01

318

Amorphous and crystalline aerosol particles interacting with water vapor - Part 1: Microstructure, phase transitions, hygroscopic growth and kinetic limitations  

NASA Astrophysics Data System (ADS)

Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we outline characteristic features and differences in the interaction of amorphous and crystalline aerosol particles with water vapor. Using a hygroscopicity tandem differential mobility analyzer (H-TDMA), we performed hydration, dehydration and cyclic hydration&dehydration experiments with aerosol particles composed of levoglucosan, oxalic acid and ammonium sulfate (diameters ~100-200 nm, relative uncertainties <0.4%, relative humidities <5% to 95% at 298 K). The measurements and accompanying Köhler model calculations provide new insights into particle microstructure, surface adsorption, bulk absorption, phase transitions and hygroscopic growth. The results of these and related investigations lead to the following main conclusions: 1. Many organic substances (including carboxylic acids, carbohydrates and proteins) tend to form amorphous rather than crystalline phases upon drying of aqueous solution droplets. Depending on viscosity and microstructure, the amorphous phases can be classified as glasses, rubbers, gels or viscous liquids. 2. Amorphous organic substances tend to absorb water vapor and undergo gradual deliquescence and hygroscopic growth at much lower relative humidity than their crystalline counterparts. 3. In the course of hydration and dehydration, certain organic substances can form rubber- or gel-like structures (supra-molecular networks) and undergo stepwise transitions between swollen and collapsed network structures. 4. Organic gels or (semi-)solid amorphous shells (glassy, rubbery, ultra-viscous) with low molecular diffusivity can kinetically limit the uptake and release of water by submicron aerosol particles on (multi-)second time scales, which may influence the hygroscopic growth and activation of aerosol particles as cloud condensation nuclei (CCN) and ice nuclei (IN). 5. The shape and porosity of amorphous and crystalline particles formed upon dehydration of aqueous solution droplets depend on chemical composition and drying conditions. The apparent volume void fractions of particles with highly porous structures can range up to ~50% or more (xerogels, aerogels). Void fractions as well as residual water in dried aerosol particles that are not water-free (due to kinetic limitations of drying or stable hydrate formation) should be taken into account in Köhler model calculations of hygroscopic growth and CCN activation. 6. For efficient description of water uptake and phase transitions of amorphous and crystalline organic and inorganic aerosol particles and particle components, we propose not to limit the terms deliquescence and efflorescence to equilibrium phase transitions of crystalline substances interacting with water vapor. Instead we propose the following generalized definitions: Deliquescence is the transformation of a (semi-)solid substance into a liquid aqueous solution, whereby water is absorbed from the gas phase ("liquefaction upon humidification/hydration"). Efflorescence is the transformation of a substance from a liquid aqueous solution into a (semi-)solid phase, whereby water is evaporated ("solidification upon drying/dehydration"). According to these definitions, individual components as well as entire aerosol particles can undergo gradual or prompt, partial or full deliquescence or efflorescence.

Mikhailov, E.; Vlasenko, S.; Martin, S. T.; Koop, T.; Pöschl, U.

2009-03-01

319

Examination of growth rate during hydride vapor phase epitaxy of GaN on ammonothermal GaN seeds  

NASA Astrophysics Data System (ADS)

One of the main advantages of the hydride vapor phase epitaxy (HVPE) method for crystallizing bulk gallium nitride is the crystallization of GaN with a relatively high growth rate (>100 ?m/h). In this paper various growth rates in the c-direction during crystallization of GaN by HVPE on ammonothermally grown GaN crystals are determined and examined. The influence of the highest (380 ?m/h) and the lowest (40 ?m/h) growth rate on the structural quality and purity of the HVPE-GaN crystals is analyzed. The optimal macroscopically stable growth rate (without cracks and pits) and the way of achieving it are presented and discussed.

Sochacki, T.; Amilusik, M.; Fijalkowski, M.; Lucznik, B.; Weyher, J. L.; Grzegory, I.; Kucharski, R.; Iwinska, M.; Bockowski, M.

2014-12-01

320

Formation of magnetic nanocolumns during vapor phase deposition of a metal-polymer nanocomposite: experiments and kinetic Monte Carlo simulations  

E-print Network

Metal-polymer nanocomposites have been investigated extensively during the last years due to their interesting functional applications. They are often produced by vapor phase deposition which generally leads to the self-organized formation of spherical metallic nanoparticles in the organic matrix, while nanocolumns are only obtained under very specific conditions. Experiments\\cite{Grev+06} have shown that co-evaporation of the metallic and organic components in a simple single-step process can give rise to the formation of ultrahigh-density Fe-Ni-Co nanocolumnar structures embedded in a fluoropolymer matrix. Here we present a kinetic Monte Carlo approach which is based on an new model involving the depression of the melting point on the nanoscale and a critical nanoparticle size required for solidification. In addition we present new experimental results down to a deposition temperature of \\cel{-70} and also report the magnetic properties. The simulations provide a detailed understanding of the transition fro...

Rosenthal, L; Zaporojtchenko, V; Strunskus, T; Faupel, F; Bonitz, M

2013-01-01

321

Photoassisted metalorganic vapor-phase epitaxy of nitrogen-doped ZnSe using tertiarybutylamine as doping source  

NASA Astrophysics Data System (ADS)

Nitrogen doping into ZnSe was carried out by photoassisted metalorganic vapor-phase epitaxy using diethylzinc and dimethylselenium. Tertiarybutylamine (t-BNH2) was used as a doping source. Photo luminescence, electrical properties of Schottky diodes, and electroluminescence from ZnSe:N/n-ZnSe:Ga diodes revealed acceptor incorporation and p-type behaviour in the ZnSe:N layers. Low temperature (350 C) growth and low irradiation intensity (4 5 mW/cm(exp 2)) were found to desirable for effective doping. As an example, for the ZnSe:N layer with nitrogen concentration of 5 x 10(exp 17) cm(exp -3) revealed by secondary ions mass spectroscopy, net acceptor concentration was estimated to be 2 x 10(exp 17) cm(exp -3) from capacitance measurements of the Schottky diodes as a first approximation.

Fujita, Shizuo; Asano, Takeharu; Maehara, Kensaku; Fujita, Shigeo

1993-08-01

322

Photoassisted Metalorganic Vapor-Phase Epitaxy of Nitrogen-Doped ZnSe Using Tertiarybutylamine as Doping Source  

NASA Astrophysics Data System (ADS)

Nitrogen doping into ZnSe was carried out by photoassisted metalorganic vapor-phase epitaxy using diethylzinc and dimethylselenium. Tertiarybutylamine (t-BNH2) was used as a doping source. Photoluminescence, electrical properties of Schottky diodes, and electroluminescence from ZnSe:N/n-ZnSe:Ga diodes revealed acceptor incorporation and p-type behavior in the ZnSe:N layers. Low-temperature (350 °C) growth and low irradiation intensity (45 mW/cm2) were found to be desirable for effective doping. As an example, for the ZnSe:N layer with nitrogen concentration of 5× 1017 cm-3 revealed by secondary ion mass spectroscopy, net acceptor concentration was estimated to be 2× 1017 cm-3 from capacitance measurements of the Schottky diodes as a first approximation.

Fujita, Shizuo; Asano, Takeharu; Maehara, Kensaku; Fujita, Shigeo

1993-08-01

323

On the formation of the SbGa heteroantisite in metalorganic vapor-phase epitaxial GaAs:Sb  

NASA Astrophysics Data System (ADS)

Metalorganic vapor-phase epitaxial growth of GaAs doped with isovalent Sb is reported. By increasing the trimethylantimony concentration during growth the total Sb concentration was varied between 1×1017-1×1019 cm-3. A new deep level defect with an activation energy of the thermal emission rates of Ec-0.54 eV is observed. The defect concentration increases with increasing As partial pressure and with increasing Sb doping. It is also found that the EL2 concentration decreases with increasing Sb doping. The new energy level is suggested to be the 0/+ transition of the SbGa heteroantisite defect. No photocapacitance quenching effect, reflecting a metastable state as seen for EL2(AsGa), is observed for SbGa.

Yakimova, R.; Omling, P.; Yang, B. H.; Samuelson, L.; Fornell, J.-O.; Ledebo, L.

1991-09-01

324

Single-monolayer quantum wells of GaInAs in InP grown by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

GaInAs/InP quantum wells differing in thickness between 1 and 20 monolayers (1 monolayer?2.93 Å) have been grown by low-pressure (50 mbar) metalorganic vapor phase epitaxy and investigated by 2 K photoluminescence. To our knowledge this is the first observation of the one monolayer quantum well. Well-resolved photoluminescence peaks were observed and were attributed to recombination of excitons bound to quantum wells of defined monolayer thickness. The growth rate could be adjusted to produce a one monolayer quantum well. Its photoluminescence peak was observed at 1.245 eV, corresponding to a quantum confinement shift of 434 meV. The full width at half maximum of this peak was only 8 meV.

Seifert, W.; Fornell, J.-O.; Ledebo, L.; Pistol, M.-E.; Samuelson, L.

1990-03-01

325

Testing of Performance of a Scroll Pump in Support of Improved Vapor Phase Catalytic Ammonia Removal (VPCAR) Mass Reduction  

NASA Technical Reports Server (NTRS)

This paper describes the results of ground testing of a scroll pump with a potential of being a substitute for the current vacuum pump of the Vapor Phase Catalytic Ammonia Reduction (VPCAR). Assessments of the pressure-time, pump-down time, pump power and the pump noise were made for three configurations of the pump the first of which was without the gas ballast, the second with the gas ballast installed but not operating and the third with the gas ballast operating. The tested scroll pump exhibited optimum characteristics given its mass and power requirements. The pump down time required to reach a pressure of 50 Torr ranged from 60 minutes without the ballast to about 120 minutes with the gas ballast operational. The noise emission and the pump power were assessed in this paper as well.

Nahra, Henry K.; Kraft, Thomas G.; Yee, Glenda F.; Jankovsky, Amy L.; Flynn, Michael

2006-01-01

326

Postgrowth Annealing of CdTe Layers Grown on Si Substrates by Metalorganic Vapor-Phase Epitaxy  

NASA Astrophysics Data System (ADS)

Annealing conditions of CdTe layers grown on Si substrates by metalorganic vapor-phase epitaxy were studied. Typically, 3- ?m-thick n-type (211) CdTe layers were annealed for 60 s in flowing hydrogen at atmospheric pressure by covering their surfaces with bulk CdTe wafers. At annealing temperatures above 700°C, improvement of crystal quality was confirmed from full-width at half-maximum values of double-crystal rocking-curve measurements and x-ray diffraction measurements. Photoluminescence measurements revealed no deterioration of electrical properties in the annealed n-CdTe layers. Furthermore, annealing at 900°C improved the performance of radiation detectors with structure of p-like CdTe/ n-CdTe/ n +-Si substrate.

Yasuda, K.; Niraula, M.; Namba, S.; Kondo, T.; Muramatsu, S.; Yamashita, H.; Wajima, Y.; Agata, Y.

2013-11-01

327

Metalorganic vapor phase epitaxy of GaAs on Si using II a-flouride buffer layers  

NASA Astrophysics Data System (ADS)

Metalorganic vapor phase epitaxy has been used for the first time to grow epitaxial GaAs layers on (111) and (100) oriented Si either using CaF 2 or stacked (Ca,Sr)F 2/CaF 2 as a buffer. The GaAs layers show sharp and well resolved electron channeling patterns. The Rutherford backscattering (RBS) ion channeling minimum yield is 5% for (111) orientation and 6% for (100) orientation. The GaAs(111) layers are untwinned. The strain in the GaAs layer has been measured with RBS and X-ray diffraction and it is found that the thermal mismatch-induced strain in the GaAs layer is considerably lower than in similar GaAs films grown without flouride buffer.

Tiwari, A. N.; Freundlich, A.; Beaumont, B.; Blunier, S.; Zogg, H.; Teodoropol, S.; Vèrié, C.

1992-11-01

328

Growth of thick GaN layers on laser-processed sapphire substrate by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

A 600 ?m thick GaN layer was successfully grown by hydride vapor phase epitaxy by replacing the standard sapphire substrate with that processed by a focused laser beam within the substrate. The effects of the laser processing on the curvature and cracking of the GaN layer were investigated. Microscopic observations of the interior of the thick GaN layer revealed that the laser-processed substrate suppressed the generation of microcracks in the GaN layer. In addition, the laser processing was also found to reduce the change in the curvature during the GaN layer growth in comparison to that on the standard substrate. It is shown that the overlapping microcracks observed in the GaN layer on the standard sapphire substrate lead to serious cracking after thick GaN layer growth.

Koyama, Koji; Aida, Hideo; Kim, Seong-Woo; Ikejiri, Kenjiro; Doi, Toshiro; Yamazaki, Tsutomu

2014-10-01

329

A model for arsenic anti-site incorporation in GaAs grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

GaAs growth by hydride vapor phase epitaxy (HVPE) has regained interest as a potential route to low cost, high efficiency thin film photovoltaics. In order to attain the highest efficiencies, deep level defect incorporation in these materials must be understood and controlled. The arsenic anti-site defect, AsGa or EL2, is the predominant deep level defect in HVPE-grown GaAs. In the present study, the relationships between HVPE growth conditions and incorporation of EL2 in GaAs epilayers were determined. Epitaxial n-GaAs layers were grown under a wide range of deposition temperatures (TD) and gallium chloride partial pressures (PGaCl), and the EL2 concentration, [EL2], was determined by deep level transient spectroscopy. [EL2] agreed with equilibrium thermodynamic predictions in layers grown under conditions in which the growth rate, RG, was controlled by conditions near thermodynamic equilibrium. [EL2] fell below equilibrium levels when RG was controlled by surface kinetic processes, with the disparity increasing as RG decreased. The surface chemical composition during growth was determined to have a strong influence on EL2 incorporation. Under thermodynamically limited growth conditions, e.g., high TD and/or low PGaCl, the surface vacancy concentration was high and the bulk crystal was close to equilibrium with the vapor phase. Under kinetically limited growth conditions, e.g., low TD and/or high PGaCl, the surface attained a high GaCl coverage, blocking As adsorption. This competitive adsorption process reduced the growth rate and also limited the amount of arsenic that incorporated as AsGa. A defect incorporation model which accounted for the surface concentration of arsenic as a function of the growth conditions, was developed. This model was used to identify optimal growth parameters for the growth of thin films for photovoltaics, conditions in which a high growth rate and low [EL2] could be attained.

Schulte, K. L.; Kuech, T. F.

2014-12-01

330

Vaporization as a Smokeless Cannabis Delivery System: A Pilot Study  

Microsoft Academic Search

Although cannabis may have potential therapeutic value, inhalation of a combustion product is an undesirable delivery system. The aim of the study was to investigate vaporization using the Volcano® device as an alternative means of delivery of inhaled Cannabis sativa. Eighteen healthy inpatient subjects enrolled to compare the delivery of cannabinoids by vaporization to marijuana smoked in a standard cigarette.

D I Abrams; H P Vizoso; S B Shade; C Jay; M E Kelly; N L Benowitz; DI Abrams

2007-01-01

331

Enhanced quality thin film Cu(In,Ga)Se[sub 2] for semiconductor device applications by vapor-phase recrystallization  

DOEpatents

Enhanced quality thin films of Cu[sub w](In,Ga[sub y])Se[sub z] for semiconductor device applications are fabricated by initially forming a Cu-rich, phase-separated compound mixture comprising Cu(In,Ga):Cu[sub x]Se on a substrate to form a large-grain precursor and then converting the excess Cu[sub x]Se to Cu(In,Ga)Se[sub 2] by exposing it to an activity of In and/or Ga, either in vapor In and/or Ga form or in solid (In,Ga)[sub y]Se[sub z]. Alternatively, the conversion can be made by sequential deposition of In and/or Ga and Se onto the phase-separated precursor. The conversion process is preferably performed in the temperature range of about 300--600 C, where the Cu(In,Ga)Se[sub 2] remains solid, while the excess Cu[sub x]Se is in a liquid flux. The characteristic of the resulting Cu[sub w](In,Ga)[sub y]Se[sub z] can be controlled by the temperature. Higher temperatures, such as 500--600 C, result in a nearly stoichiometric Cu(In,Ga)Se[sub 2], whereas lower temperatures, such as 300--400 C, result in a more Cu-poor compound, such as the Cu[sub z](In,Ga)[sub 4]Se[sub 7] phase. 7 figs.

Tuttle, J.R.; Contreras, M.A.; Noufi, R.; Albin, D.S.

1994-10-18

332

Smectics and smectic-like phases: Equation of state, finite size effects and vapor pressure paradox  

Microsoft Academic Search

In this dissertation, I pursue the constant pressure ensemble approach to elucidate the statistical mechanics of smectic phases of semi-flexible manifolds. I use this approach to consider in detail sterically stabilized phases of semi-flexible polymers in two-dimensional smectic systems. For the first time, the universal constants characterizing the entropic repulsion between semi-flexible polymers are obtained. The thermodynamic limit is quickly

Lianghui Gao

2004-01-01

333

Electronic-Cigarette Smoking Experience Among Adolescents  

Microsoft Academic Search

ObjectivesTo investigate the level of awareness and contact routes to electronic cigarette (e-cigarette), and to identify significant factors that may affect adolescent use of e-cigarettes; this study explores the experience of e-cigarettes among adolescents.

Jun Ho Cho; Eunyoung Shin; Sang-Sik Moon

2011-01-01

334

Cigarette Advertisements and Youth Attitudes about Smoking  

Microsoft Academic Search

Cigarette advertisements are commonly believed to play an important causal role in encouraging youth to start smoking. The 1998 Master Settlement Agreement between cigarette manufacturers and the states included a ban on cigarette advertising that targets youth. The 2009 Family Smoking Prevention and Tobacco Control Act – which granted regulatory authority over the cigarette industry to the Food and Drug

Donald Kenkel; Hua Wang

2010-01-01

335

An international analysis of cigarette affordability  

PubMed Central

Objective: To investigate how affordable cigarettes are in developed and developing countries, and to calculate by how much the affordability of cigarettes has changed between 1990 and 2001; and secondly, to investigate the relation between cigarette affordability and consumption. Design: Affordability was defined as the cost of cigarettes relative to per capita income. Trends in cigarette affordability, and affordability elasticities of demand, were estimated using regression techniques. Subjects: Seventy countries were investigated, of which 28 are categorised as high income developed countries, while 42 are categorised as developing countries. Cigarette prices were obtained for the main city/cities in the countries. Results: Despite the fact that cigarettes are more expensive in developed countries, the high levels of income make cigarettes more affordable in these countries vis-à-vis developing countries. Of the 28 developed countries, cigarettes became more affordable in 11 and less affordable in 17 countries during the 1990s. Of the 42 developing countries, cigarettes became more affordable in 24 and less affordable in 18 countries. Based on a cross sectional analysis, a 1% increase in the relative income price (the inverse of cigarette affordability) is expected to decrease cigarette consumption by between 0.49–0.57%. Conclusions: Cigarette affordability, more than just the price, determines cigarette consumption. While cigarettes have become more affordable in many developing countries, some developing countries (for example, South Africa, Poland, and Thailand) have implemented strong and effective tobacco control policies, and have been able to decrease cigarette consumption as a result. PMID:15564616

Blecher, E; van Walbeek, C P

2004-01-01

336

27 CFR 41.34 - Cigarette papers.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Cigarette papers. 41.34 Section 41.34 Alcohol...IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.34 Cigarette papers. Cigarette papers are taxed at...

2010-04-01

337

Functional Analysis and Treatment of Cigarette Pica.  

ERIC Educational Resources Information Center

This study of an adolescent with mental retardation and autism found that pica of cigarette butts was maintained in a condition with no social consequences when cigarettes contained nicotine but not when cigarettes contained herbs without nicotine. A procedure based on stimulus control, which reduced cigarette consumption to zero, is described.…

Piazza, Cathleen C.; And Others

1996-01-01

338

Vapor-phase-deposited organosilane coatings as hardening agents for high-peak-power laser optics  

NASA Astrophysics Data System (ADS)

Multilayer-dielectric (MLD) diffraction gratings are used in high-power laser systems to compress laser-energy pulses. The peak power deliverable on target for these short-pulse petawatt class systems is limited by the laser-damage resistance of the optical components in the system, especially the MLD gratings. Recent experiments in our laboratory have shown that vapor treatment of MLD gratings at room temperature with organosilanes such as hexamethyldisilazane (HMDS) produces an increase in their damage threshold at 1054 nm (10-ps, 370- ?m spot size) as compared to uncoated MLD grating control samples. The 1-on-1 laser-damage threshold of an HMDS-treated grating increased by 4.5% as compared to the uncoated control sample, while the N-on-1 damage threshold of an MLD grating treated with tetramethyldisilazane increased by 16.5%. For an MLD grating treated with bis-(trifluoropropyl)tetramethyldisilazane, the N-on-1 and 1-on-1 damage thresholds increased by 4.8% and 5.3%, respectively. Such increases in laser-damage threshold are unprecedented and counterintuitive because it is widely believed that the presence of organic materials or coatings on the surfaces of optical substrates will inevitably lead to reduced laser-damage resistance.

Marshall, K. L.; Culakova, Z.; Ashe, B.; Giacofei, C.; Rigatti, A. L.; Kessler, T. J.; Schmid, A. W.; Oliver, J. B.; Kozlov, A.

2007-09-01

339

Vapor phase growth of titania whiskers by hydrolysis of titanium flouride  

NASA Astrophysics Data System (ADS)

The chemical vapor deposition of TiO 2 crystals from the system TiF 4-H 2O was studied at elevated temperatures. When Na 2TiF 6 was used as a TiF 4 source, rutile-type TiO 2 needles grew to 30 mm in length in a comparatively short time over the melt in a platinum crucible in air. The needles were mostly skeletal or twinned intergrowths of acicular crystals. Rutile gradually changed to Na 2Ti 6O 13 by the reaction with NaF and moisture in the air. The formation of Na 2Ti 6O 13 was inhibited by addition of TiO 2 to the raw material. The rutile whiskers were grown under controlled conditions by means of a flow method from the system Na 2TiF 6-TiO 2-H 2O. The needles or whiskers were found to grow preferentially in the [001] direction.

Oota, Toshitaka; Yamai, Iwao; Yokoyama, Mitsunori

1984-04-01

340

Metalorganic vapor phase epitaxy growth of ternary tetradymite Bi2Te3-xSex compounds  

NASA Astrophysics Data System (ADS)

We report on a metal organic vapor epitaxy (MOVPE) of Bi2Te3-xSex films over the entire range of compositions (0 ? x ? 3) for the first time. The films were grown on Al2O3(0001) substrates at 465 °C using trimethylbismuth (Bi2Me3), diethyltellurium (Et2Te) and diisopropylselenium (iPro2Se) as metalorganic sources. To realize the 2D growth mode and to grow films with flat surfaces and high crystalline quality, a thin ZnTe buffer layer was used. As-grown films were studied using optical and AFM microscopy techniques and X-ray diffraction. It was found that under steady growth conditions the composition of Bi2Te3-xSex films strongly depends on the film thickness. But a high rate of interdiffusion of chalcogens at the growth temperature rapidly leads to a homogeneous composition of the film in the growth direction. Dependence of the intensity of X-ray reflection (0012) on the composition of Bi2Te3-xSex films x has extremes near x=1 (Bi2Te2 Se) and x=2 (Bi2Se2 Te). The AFM micrographs and profiles show large (above 2 ?m) triangle-shaped atomically flat terraces with step height of a quintuple layer (0.90 nm) of the tetradymite-type compounds. The electronic properties of the grown films have been characterized via four probe magnetotransport measurements.

Kuznetsov, P. I.; Yakushcheva, G. G.; Luzanov, V. A.; Temiryazev, A. G.; Shchamkhalova, B. S.; Jitov, V. A.; Sizov, V. E.

2015-01-01

341

Metalorganic vapor phase epitaxy and characterizations of nearly-lattice-matched AlInN alloys on GaN/sapphire templates and  

E-print Network

Metalorganic vapor phase epitaxy and characterizations of nearly-lattice-matched AlInN alloys on GaN/sapphireInN on GaN templates residing on sapphire and free-standing GaN substrates were performed, and the results

Gilchrist, James F.

342

InAsP\\/InP(001) quantum dots emitting at 1.55 ?m grown by metalorganic vapor phase epitaxy  

Microsoft Academic Search

This contribution reports the growth of InAsP quantum dots on InP(001) using metalorganic vapor phase epitaxy. We show that the control of the voluntary phosphorus incorporation into the quantum dots allows both to tune their emission to 1.55 mum and to improve their optical properties.

A. Michon; R. Hostein; G. Patriarche; G. Beaudoin; N. Gogneau; A. Beveratos; I. Robert-Philip; I. Sagnes; S. Laurent; S. Sauvage; P. Boucaud

2008-01-01

343

Secondary phase formation and the microstructural evolution of surface layers during vapor phase alteration of the French SON 68 nuclear waste glass at 200{degrees}C  

SciTech Connect

The SON 68 inactive {open_quotes}R7T7{close_quotes} composition is the French reference glass for the LWR nuclear waste glass. Vapor phase alteration was used to accelerate the reaction progress of glass corrosion and to develop the characteristic suite of secondary, alteration phases. Extensive solid-state characterization (AEM/SEM/HRTEM) was completed on six inactive R7T7 waste glasses which were altered in the presence of saturated water vapor (200{degrees}C) for 91, 241, 908, 1000, 1013, and 1021 days. The AEM samples were examined in cross-section (lattice-fringe imaging, micro-diffraction, and quantitative thin-film EDS analysis). The glass monoliths were invariably covered with a thin altered rind. The layer became thicker with time: 0.5 {mu}m for 22 days; 4 {mu}m for 91 days; 6 {mu}m for 241 days; 10 {mu}m for 908 days; 26 {mu}m for 1013 days; and <35 {mu}m for 1021 days. The composite alteration layer of the SON 68 samples is at least four time less thick than that of the SRL 131 glass composition. Six distinctive zones, based on phase chemistry and microstructure, were distinguished within the well-developed surface layers. Numerous crystalline phases such as analcime, tobermorite, apatite, and weeksite were identified on the surfaces of the reacted glasses as precipitates. Two crystalline phases, Ag{sub 2}TeO{sub 3} and (Ca,Sr)Mo{sub 3}O{sub 9}(OH){sub 2}, were found within the inner zones of surface layers, and they must have nucleated in situ, indicating that Ag, Te, Sr, and Mo can be retained within the surface layer. The majority of the surface layer volume is composed of two morphologically and chemically different structures: one consists of well-crystallized fibrous smectite aggregates occurring along with cavities, the A-domain; and the other consists of poorly-crystallized regions containing needle-like smectite (montmorillonite) crystallites, a silica-rich amorphous matrix, and possibly ZrO{sub 2} particles, the B-domain.

Gong, W.L.; Ewing, R.C.; Wang, L.M. [Univ. of New Mexico, Albuquerque, NM (United States)] [and others

1995-12-31

344

Vapor-Phase Metalation by Atomic Layer Deposition in a Metal-Organic Framework  

E-print Network

, thermally stable, Zr-based MOF with spatially oriented -OH groups and large 1D mesopores and apertures, Noakowskiego 3, 00-664 Warsaw, Poland *S Supporting Information ABSTRACT: Metal-organic frameworks (MOFs) have. Most commonly, MOFs have been metalated from the condensed phase (i.e., from solution). Here we

345

Predictors of Marijuana Relapse in the Human Laboratory: Robust Impact of Tobacco Cigarette Smoking Status  

PubMed Central

Background Few marijuana smokers in treatment achieve sustained abstinence, yet factors contributing to high relapse rates are unknown. Study 1: Methods Data from five inpatient laboratory studies assessing marijuana intoxication, withdrawal and relapse were combined to assess factors predicting the likelihood and severity of relapse. Daily, nontreatment-seeking marijuana smokers (n=51; 10 ± 5 marijuana cigarettes/day) were enrolled. Results 49% of participants relapsed the first day active marijuana became available. Tobacco cigarette smokers (75%), who were not abstaining from cigarettes, were far more likely to relapse than non-cigarette smokers (OR=19, p<0.01). Individuals experiencing more positive subjective effects (i.e. feeling “high”) after marijuana administration and those with more negative affect and sleep disruption during marijuana withdrawal were more likely to have severe relapse episodes (p<0.05). Study 2: Methods To isolate the effects of cigarette smoking, marijuana intoxication, withdrawal and relapse were assessed in daily marijuana and cigarette smokers (n=15) under two within-subject, counter-balanced conditions: while smoking tobacco cigarettes as usual (SAU) and after at least 5 days without cigarettes (Quit). Results Most participants (87%) relapsed to marijuana whether in the SAU or Quit phase. Tobacco cigarette smoking did not significantly influence relapse, nor did it affect marijuana intoxication or most symptoms of withdrawal relative to tobacco cessation. Conclusions Daily marijuana smokers who also smoke cigarettes have high rates of marijuana relapse and cigarette smoking versus recent abstinence does not directly influence this association. These data indicate that current cigarette smoking is a clinically important marker for increased risk of marijuana relapse. PMID:22939992

Haney, Margaret; Bedi, Gillinder; Cooper, Ziva D.; Glass, Andrew; Vosburg, Suzanne K.; Comer, Sandra D.; Foltin, Richard W.

2012-01-01

346

Vapor-phase synthesis of a solid precursor for {alpha}-alumina through a catalytic decomposition of aluminum triisopropoxide  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer A new solid precursor for {alpha}-alumina was prepared at about 200 Degree-Sign C from aluminum tri-isopropoxide vapor. Black-Right-Pointing-Pointer The obtained precursor was calcined at 1200 Degree-Sign C to form {alpha}-alumina particles, 75 nm in surface area equivalent diameter. Black-Right-Pointing-Pointer The weight loss of the precursor upon calcination was 24%, lower than that of Al(OH){sub 3}, a conventional alumina precursor. -- Abstract: A new solid precursor, hydrous aluminum oxide, for {alpha}-alumina nanoparticles was prepared by thermal decomposition of aluminum triisopropoxide (ATI) vapor in a 500 mL batch reactor at 170-250 Degree-Sign C with HCl as catalyst. The conversion of ATI increased with increasing temperature and catalyst content; it was nearly complete at 250 Degree-Sign C with the catalyst at 10 mol% of the ATI. The obtained precursor particles were amorphous, spherical and loosely agglomerated. The primary particle size is in the range 50-150 nm. The ignition loss of the precursor was 24%, considerably lower than 35% of Al(OH){sub 3}, the popular precursor for alumina particles. Upon calcination of the precursor at 1200 Degree-Sign C in the air with a heating rate of 10 Degree-Sign C/min and a holding time of 2 h, the phase was completely transformed into {alpha}. The spherical particles composing the precursor turned worm-like by the calcination probably due to sintering between neighboring particles. The surface area equivalent diameter of the resulting {alpha}-alumina was 75 nm.

Nguyen, Tu Quang [Department of Chemical Engineering, Kongju National University, 275 Budae-dong, Cheonan, Chungnam 330-717 (Korea, Republic of)] [Department of Chemical Engineering, Kongju National University, 275 Budae-dong, Cheonan, Chungnam 330-717 (Korea, Republic of); Park, Kyun Young, E-mail: kypark@kongju.ac.kr [Department of Chemical Engineering, Kongju National University, 275 Budae-dong, Cheonan, Chungnam 330-717 (Korea, Republic of); Jung, Kyeong Youl [Department of Chemical Engineering, Kongju National University, 275 Budae-dong, Cheonan, Chungnam 330-717 (Korea, Republic of)] [Department of Chemical Engineering, Kongju National University, 275 Budae-dong, Cheonan, Chungnam 330-717 (Korea, Republic of); Cho, Sung Baek [Korea Institute of Geoscience and Mineral Resources (KIGAM), 92 Gwahang-no, Yuseong-gu 305-350 (Korea, Republic of)] [Korea Institute of Geoscience and Mineral Resources (KIGAM), 92 Gwahang-no, Yuseong-gu 305-350 (Korea, Republic of)

2011-12-15

347

NOVEL PROCESS FOR REMOVAL AND RECOVERY OF VAPOR-PHASE MERCURY  

SciTech Connect

The goal of this project is to investigate the use of a regenerable sorbent for removing and recovering mercury from the flue gas of coal-fired power plants. The process is based on the sorption of mercury by noble metals and the thermal regeneration of the sorbent, recovering the desorbed mercury in a small volume for recycling or disposal. The project was carried out in two phases, covering five years. Phase I ran from September 1995 through September 1997 and involved development and testing of sorbent materials and field tests at a pilot coal-combustor. Phase II began in January 1998 and ended September 2000. Phase II culminated with pilot-scale testing at a coal-fired power plant. The use of regenerable sorbents holds the promise of capturing mercury in a small volume, suitable for either stable disposal or recycling. Unlike single-use injected sorbents such as activated carbon, there is no impact on the quality of the fly ash. During Phase II, tests were run with a 20-acfm pilot unit on coal-combustion flue gas at a 100 lb/hr pilot combustor and a utility boiler for four months and six months respectively. These studies, and subsequent laboratory comparisons, indicated that the sorbent capacity and life were detrimentally affected by the flue gas constituents. Sorbent capacity dropped by a factor of 20 to 35 during operations in flue gas versus air. Thus, a sorbent designed to last 24 hours between recycling lasted less than one hour. The effect resulted from an interaction between SO{sub 2} and either NO{sub 2} or HCl. When SO{sub 2} was combined with either of these two gases, total breakthrough was seen within one hour in flue gas. This behavior is similar to that reported by others with carbon adsorbents (Miller et al., 1998).

Craig S. Turchi

2000-09-29

348

Characteristics of bulk InGaAsSbN/GaAs grown by metalorganic vapor phase epitaxy (MOVPE)  

NASA Astrophysics Data System (ADS)

Bulk, lattice-matched dilute-nitride-antimonide materials were grown by metalorganic vapor phase epitaxy (MOVPE) for integration into multi-junction solar cells. Bulk nominally lattice-matched films of InGaAsN and InGaAsSbN with band gap energies in the 1-1.3 eV range are characterized for background carrier concentration and luminescent properties, two factors of importance for solar cell applications. The intrinsic carbon and free carrier (hole) concentration is found to be sensitive to the selection of the gallium metalorganic source and the gas-phase MOVPE growth conditions. Variable temperature (40-300 K) steady-state photoluminescence (PL) measurements of InGaAsSbN indicate that carrier localization occurs at low temperature, similar to that commonly observed for InGaAsN materials. Carrier lifetimes of up to ˜202 ps were obtained from double heterostructures incorporating InGaAsSbN materials using time-resolved photoluminescence (TR-PL) spectroscopy.

Kim, T. W.; Garrod, T. J.; Mawst, L. J.; Kuech, T. F.; LaLumondiere, S. D.; Sin, Y.; Lotshaw, W. T.; Moss, S. C.

2013-05-01

349

Characterization and modeling of a liquid-vapor phase change membrane actuator with integrated SU-8 micro capillary wicking structure.  

SciTech Connect

A liquid-vapor phase-change membrane actuator is demonstrated which integrates an open groove wicking structure to continuously pump liquid into the heat addition region of the pressure cavity. Integration of the wick yields a higher efficiency and operating speed compared with existing thermal phase-change actuators. This improvement results from control of the liquid thickness, volume, and fill rate. An experimentally validated numerical model is presented which determines the energy budget within the actuator and investigates factors controlling efficiency such as wick thickness, thermal mass, thermal conductivity, and membrane compliance. Work to date for this class of actuators has focused primarily on steady state behavior with detailed transient analyses receiving little attention. This investigation focuses strictly on characterization of transient operation and provides a benchmark for this class of dynamic thermal actuators. The actuator presented in this work develops pressure and deflection excursions of 148 kPa and 70 {micro}m at 10 Hz while consuming 150 mW. A peak force of 1.4 N is generated during each cycle and the thermal to mechanical efficiency is 0.11%.

Richards, R. (Washington State University); Won, S.Y. (Washington State University); Whalen, Scott; Richards, C. (Washington State University); Bahr, David F. (Washington State University)

2005-04-01

350

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

USGS Publications Warehouse

[1] 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 nonreactive or relatively inert gases such as Ar and N2 can be effectively used to better understand and quantify physical and chemical processes related to methanogenic activity in the subsurface. In the vadose zone, regions of Ar and N2 depletion and enrichment are indicative of methanogenic and methanotrophic zones, and concentration gradients between the regions suggest that reaction-induced advection can be an important gas transport process. In the saturated zone, dissolved Ar and N2 concentrations are used to quantify degassing driven by methanogenesis and also suggest that attenuation of methane along the flow path, into the downgradient aquifer, is largely controlled by physical processes. Slight but discernable preferential depletion of N2 over Ar, in both the saturated and unsaturated zones near the free-phase oil, suggests reactivity of N2 and is consistent with other evidence indicating that nitrogen fixation by microbial activity is taking place at this site. Copyright 2005 by the American Geophysical Union.

Amos, R.T.; Mayer, K.U.; Bekins, B.A.; Delin, G.N.; Williams, R.L.

2005-01-01

351

Riemannian geometry study of vapor-liquid phase equilibria and supercritical behavior of the Lennard-Jones fluid.  

PubMed

The behavior of thermodynamic response functions and the thermodynamic scalar curvature in the supercritical region have been studied for a Lennard-Jones fluid based on a revised modified Benedict-Webb-Rubin equation of state. Response function extrema are sometimes used to estimate the Widom line, which is characterized by the maxima of the correlation lengths. We calculated the Widom line for the Lennard-Jones fluid without using any response function extrema. Since the volume of the correlation length is proportional to the Riemannian thermodynamic scalar curvature, the locus of the Widom line follows the slope of maximum curvature. We show that the slope of the Widom line follows the slope of the isobaric heat capacity maximum only in the close vicinity of the critical point and that, therefore, the use of response function extrema in this context is problematic. Furthermore, we constructed the vapor-liquid coexistence line for the Lennard-Jones fluid using the fact that the correlation length, and therefore the thermodynamic scalar curvature, must be equal in the two coexisting phases. We compared the resulting phase envelope with those from simulation data where multiple histogram reweighting was used and found striking agreement between the two methods. PMID:22587083

May, Helge-Otmar; Mausbach, Peter

2012-03-01

352

The Case in Favor of E-Cigarettes for Tobacco Harm Reduction  

PubMed Central

A carefully structured Tobacco Harm Reduction (THR) initiative, with e-cigarettes as a prominent THR modality, added to current tobacco control programming, is the most feasible policy option likely to substantially reduce tobacco-attributable illness and death in the United States over the next 20 years. E-cigarettes and related vapor products are the most promising harm reduction modalities because of their acceptability to smokers. There are about 46 million smokers in the United States, and an estimated 480,000 deaths per year attributed to cigarette smoking. These numbers have been essentially stable since 2004. Currently recommended pharmaceutical smoking cessation protocols fail in about 90% of smokers who use them as directed, even under the best of study conditions, when results are measured at six to twelve months. E-cigarettes have not been attractive to non-smoking teens or adults. Limited numbers non-smokers have experimented with them, but hardly any have continued their use. The vast majority of e-cigarette use is by current smokers using them to cut down or quit cigarettes. E-cigarettes, even when used in no-smoking areas, pose no discernable risk to bystanders. Finally, addition of a THR component to current tobacco control programming will likely reduce costs by reducing the need for counseling and drugs. PMID:25003176

Nitzkin, Joel L.

2014-01-01

353

Treatment of Produced Waters Using a Surfactant Modified Zeolite/Vapor Phase Bioreactor System  

SciTech Connect

This report summarizes work performed on this project from April 2004 through September 2004. Our previous work demonstrated that a polyurethane foam biofilter could successfully biodegrade the BTEX contaminants found in the SMZ regeneration waste gas stream. However, establishing the biomass on the polyurethane foam packing was relatively time consuming and daily recirculation of a concentrated nutrient solution was required for efficient operation of the foam biofilter. To simplify the start up and operating requirements of the biofilter system, a simple, compost-based biofilter was investigated for its ability to treat the BTEX contaminants generated during the SMZ regeneration process. The investigation of the compost biofilter was divided into three experimental phases that spanned 180 days of biofilter operation. During Phase 1, the biofilter was continuously supplied a BTEX-contaminated waste gas stream. During Phase 2, a series of periodic shutdown tests were conducted to assess how the biofilter responded when the BTEX feed was discontinued for periods ranging from 1 day to 2.8 days. The Phase 3 experiments focused on determining how the biofilter would handle periodic spikes in inlet BTEX concentration as would be expected when it is coupled with an SMZ column. Results from the continuous feed (Phase 1) experiments demonstrated that the compost biofilter could maintain BTEX removals of greater than 98% within two weeks of startup. Results of the shutdown experiments indicated that benzene removal was the most sensitive to interruptions in the BTEX feed. Nevertheless, the BTEX removal efficiency exceeded 95% within 6 hours of reestablishing the BTEX feed to the biofilter. When the biofilter was subjected to periodic spikes in BTEX concentration (Phase 3), it was found that the total BTEX removal efficiency stabilized at approximately 75% despite the fact that the biofilter was only fed BTEX contaminants 8 hours per day. Finally, the effects of nutrient supply and EBCT on compost biofilter performance were also investigated. The bioreactor maintained greater than 95% removal efficiency for over 40 days without an additional supply of nutrients when a 10X concentrated HCMM was mixed with the compost packing at the beginning of the experiments. Results also suggest that an EBCT greater than 30 seconds is required to maintain high BTEX removal efficiencies in the compost biofilter system.

Lynn E. Katz; Kerry A. Kinney; R. S. Bowman; E. J. Sullivan

2004-09-11

354

International cigarette labelling practices  

PubMed Central

DESIGN—Cross-sectional study.?PARTICIPANTS—Members of GLOBALink (www.globalink.org), an internet listserve for tobacco activists with members in 56 countries, who were asked to provide specific information on cigarette warning requirements in their countries.?MAIN OUTCOME MEASURES—Presence of specific warning labels, overall content score (based on a 0-10 scale with a point for each specific warning mentioned), size of warning label, location of warning label.?RESULTS—Forty-five countries (80%) responded; 40 had mandatory labelling requirements, three had voluntary agreements with the industry and two had no requirements. In general, American companies did no more in foreign countries than required by local law. The average developing country content score was 1.6, compared with 5.0 in developed countries (p = 0.0003). Forty-two per cent of countries either had no warning requirement or had only a very general health warning. The most common warning was for heart disease (49% of countries) and the least common was for addiction (14%). All warnings were more common in developed than developing countries. Warnings in developed country were on average 27% larger than those in developing countries (p = 0.325). Seventy-three per cent of labels in developing countries appeared only on the side of the pack, whereas 78% of labels in developed countries appeared on the front and back (p = 0.003).?CONCLUSIONS—In almost every respect measured, residents in developing countries are receiving inferior information about the hazards of smoking than residents of developed countries. Laws should be promulgated in importing and exporting countries to ensure that, where their labelling laws differ, companies would be required to provide the more comprehensive labelling.???Keywords: health warnings; cigarette pack labelling; legislation PMID:10629241

Aftab, M.; Kolben, D.; Lurie, P.

1999-01-01

355

Vapor-Phase Transport in the Near-Drift Environment at Yucca Mountain  

NASA Astrophysics Data System (ADS)

Yucca Mountain, located 160 km north of Las Vegas, Nevada, is currently being assessed as a potential site for disposal of spent nuclear fuel and high-level radioactive waste. A key issue regarding repository performance is the likelihood of precipitation percolating a vertical distance of ~300 m through unsaturated rock into drifts containing the waste packages. The amount of water that flows into drifts is thought to control the corrosion rates of waste packages, and the mobilization and transport of radionuclides. Subsequently, much effort has been directed towards estimating seepage from the near-drift environment into underground openings. While no naturally occurring seepage has been observed in the excavated tunnels and cavities at Yucca Mountain, numerical studies show that seepage can occur at steady-state percolation fluxes of tens of millimeters per year. However, under current conditions, the potential for seepage to occur naturally is greatly reduced, because of increased evaporation in the drifts resulting from ventilation. This presentation includes observations made over a period of four years along the terminal 944 m of a 2.7 km long tunnel within Yucca Mountain, commonly referred to as the Enhanced Characterization of the Repository Block which was initially excavated to study seepage into unventilated drifts. This initial objective was expanded to include an evaluation of the near-drift microclimates after large sections of the nonventilated drift were observed to be damp, or coated with beads of water, or even occasionally puddled. Observations from this effort indicate that fractures in the unsaturated zone can be primary paths for vapor flow in the immediate vicinity of emplacement drifts which is contrary to conceptual models of liquid traveling through fractures before seeping into the drifts. This work was supported by the Director, Office of Civilian Radioactive Waste Management, U.S. Department of Energy, through Memorandum Purchase Order EA9013MC5X between Bechtel SAIC Company, LLC, and the Ernest Orlando Lawrence Berkeley National Laboratory (Berkeley Lab). The support is provided to Berkeley Lab through the U.S. Department of Energy Contract No. DE-AC03-76SF00098.

Salve, R.; Kneafsey, T. J.

2003-12-01

356

Enhanced reflection via phase compensation from anomalous dispersion in atomic vapor  

SciTech Connect

The phase compensation mechanism induced by anomalous dispersion in the reflection process of four-wave mixing (or reflection from a grating) in a three-level system is investigated, where the four wave vectors do not match in vacuum. An efficiency of the reflected signal of as high as 43% from a hot atomic cell of Cs is observed. The maximum reflection occurs when the frequency of the probe beam (and consequently the frequency of the reflected signal) is slightly red detuned from the transition frequency, which is attributed to the phase compensation from the steep anomalous dispersion accompanied with a strong probe absorption. The dependences of the efficiency on the angle between the coupling and probe lights, on the intensity of the coupling, field and on atomic density are studied. A theoretical model is presented and it is in good agreement with the experimental results.

Zhang Junxiang; Zhou Haitao [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China); Wang Dawei [Beijing Computational Science Research Center, Beijing 100084 (China); Zhu Shiyao [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China); Beijing Computational Science Research Center, Beijing 100084 (China); Department of Physics, Hong Kong Baptist University (Hong Kong)

2011-05-15

357

The fire-safe cigarette.  

PubMed

Fires caused by cigarettes through the ignition of upholstered furniture and mattresses are a serious public health problem, accounting for more than 1500 deaths and 7000 serious injuries per year in the United States. Fire-resistant fabrics and stuffings, public education, and smoke detectors have had a limited impact on this problem. The federal government recently has completed a three-year study of possible modifications in cigarette design. The study has demonstrated the technical feasibility of product design changes that would substantially reduce the propensity of cigarettes to ignite fires. Legislation currently is pending in Congress and in three state legislatures to mandate a cigarette fire safety standard. This legislation deserves strong support by the medical profession. PMID:3290519

Botkin, J R

1988-07-01

358

Modification of LCAT Activity and HDL Structure New Links Between Cigarette Smoke and Coronary Heart Disease Risk  

Microsoft Academic Search

The mechanism(s) through which smoking influ- ences the progression of atherosclerosis is poorly understood. Recent evidence suggests that oxidants present in the gas phase of cigarette smoke are involved. We exposed human plasma to the filtered gas phase of cigarette smoke to assess its effects on plasma components involved in the antiatherogenic reverse cholesterol transport pathway. In our model, freshly

Mark R. McCall; Frans A. Kuypers; Diane L. Tribble; Ronald M. Krauss; Laura J. Knoff; Trudy M. Forte

2011-01-01

359

Electronic cigarettes and thirdhand tobacco smoke: two emerging health care challenges for the primary care provider  

PubMed Central

Primary care providers should be aware of two new developments in nicotine addiction and smoking cessation: 1) the emergence of a novel nicotine delivery system known as the electronic (e-) cigarette; and 2) new reports of residual environmental nicotine and other biopersistent toxicants found in cigarette smoke, recently described as “thirdhand smoke”. The purpose of this article is to provide a clinician-friendly introduction to these two emerging issues so that clinicians are well prepared to counsel smokers about newly recognized health concerns relevant to tobacco use. E-cigarettes are battery powered devices that convert nicotine into a vapor that can be inhaled. The World Health Organization has termed these devices electronic nicotine delivery systems (ENDS). The vapors from ENDS are complex mixtures of chemicals, not pure nicotine. It is unknown whether inhalation of the complex mixture of chemicals found in ENDS vapors is safe. There is no evidence that e-cigarettes are effective treatment for nicotine addiction. ENDS are not approved as smoking cessation devices. Primary care givers should anticipate being questioned by patients about the advisability of using e-cigarettes as a smoking cessation device. The term thirdhand smoke first appeared in the medical literature in 2009 when investigators introduced the term to describe residual tobacco smoke contamination that remains after the cigarette is extinguished. Thirdhand smoke is a hazardous exposure resulting from cigarette smoke residue that accumulates in cars, homes, and other indoor spaces. Tobacco-derived toxicants can react to form potent cancer causing compounds. Exposure to thirdhand smoke can occur through the skin, by breathing, and by ingestion long after smoke has cleared from a room. Counseling patients about the hazards of thirdhand smoke may provide additional motivation to quit smoking. PMID:21475626

Kuschner, Ware G; Reddy, Sunayana; Mehrotra, Nidhi; Paintal, Harman S

2011-01-01

360

Liquid-vapor phase diagram and surface properties in oppositely charged colloids represented by a mixture of attractive and repulsive Yukawa potentials.  

PubMed

The liquid-vapor phase diagrams of equal size diameter ? binary mixtures of screened potentials have been reported for several ranges of interaction using Monte Carlo simulation methods [J. B. Caballero, A. M. Puertas, A. Fern?andez-Barbero, F. J. de las Nieves, J. M. Romero-Enrique, and L. F. Rull, J. Chem. Phys. 124, 054909 (2006); A. Fortini, A.-P. Hynninen, and M. Dijkstra, J. Chem. Phys. 125, 094502 (2006)]. Both works report controversial results about the stability of the phase diagram with the inverse Debye screening length ?. Caballero found stability for values of ?? up to 20 while Fortini reported stability for ?? up to 20 while Fortini reported stability for ?? ? 4. In this work a spinodal decomposition process where the liquid and vapor phases coexist through an interface in a slab geometry is used to obtain the phase equilibrium and surface properties using a discontinuous molecular dynamics simulations for mixtures of equal size particles carrying opposite charge and interacting with a mixture of attractive and repulsive Yukawa potentials at different values of ??. An crude estimation of the triple point temperatures is also reported. The isothermal-isobaric method was also used to determine the phase stability using one phase simulations. We found that liquid-vapor coexistence is stable for values of ?? > 20 and that the critical temperatures have a maximum value at around ?? = 10, in agreement with Caballero et al. calculations. There also exists a controversy about the liquid-vapor envelope stability of the pure component attractive Yukawa model which is also discussed in the text. In addition, details about the equivalence between continuous and discontinuous molecular dynamics simulations are given, in the Appendix, for Yukawa and Lennard-Jones potentials. PMID:23406133

Chapela, Gustavo A; del Río, Fernando; Alejandre, José

2013-02-01

361

Development of a water recovery subsystem based on Vapor Phase Catalytic Ammonia Removal (VPCAR)  

NASA Technical Reports Server (NTRS)

An integrated engineering breadboard subsystem for the recovery of potable water from untreated urine was designed, fabricated and tested. It was fabricated from commercially available components without emphasis on weight, volume and power requirement optimization. Optimizing these parameters would make this process competitive with other spacecraft water recovery systems. Unlike other phase change systems, this process is based on the catalytic oxidation at elevated temperatures of ammonia and volatile hydrocarbons to innocuous products; therefore, no urine pretreatment is required. The testing program consisted of parametric tests, one month of daily tests, and a continuous run of 165 hours. The recovered water is low in ammonia, hydrocarbons and conductivity and requires only adjustment of its pH to meet drinking water standards.

Budininkas, P.; Rasouli, F.; Wydeven, T.

1986-01-01

362

Automation for monitoring of the refractive index profile of vapor-phase-deposited soot preforms for optical fiber  

SciTech Connect

The vapor-phase axial deposition process is currently one of the most advantageous methods to produce preforms for optical fibers, due to its high efficiency and reduced production cost. However, this method has great difficulty in determining the refractive index profile, since it is influenced by too many process parameters. In this work, an automation system to determine the refractive index profile by monitoring the preform deposition surface profile during the soot preform deposition stage is presented. Based on a previous study that showed a strong correlation between these two profiles, an automation system was developed in LABVIEW to monitor the deposition surface profile during the preform deposition stage in order to estimate the preform germanium doping profile and refractive index profile, as well as a theoretical study to develop this system in order to minimize the performance impairment. As a result, not only preforms with a predetermined index profile were produced but also a reduction in production cost was obtained by decreasing the number of preform rejects.

Santos, J.S. dos; Ono, E.; Suzuki, C.K. [Laboratory of Integrated Quartz Cycle (LIQC), Faculty of Mechanical Engineering, Department of Materials Engineering, State University of Campinas, P.O. Box 6122, 13083-970, Campinas-Sao Paulo (Brazil)

2006-05-15

363

Characteristics of GaSb and GaInSb layers grown by metalorganic vapor phase epitaxy  

SciTech Connect

GaInSb and GaSb layers have been grown on GaSb and GaAs substrates using metalorganic vapor phase epitaxy (MOVPE) with trimethylgallium, trimethylindium and trimethylantimony as the sources. As grown layers are p type with the carrier concentration in the mid 10{sup 16} cm{sup {minus}3} range. N type layers are grown using diethyltellurium as the Te source. Incorporation of Te in high concentration showed compensation and secondary ion mass spectrometry (SIMS) result showed that only 2.5% of Te are active when 2 {times} 10{sup 19} cm{sup {minus}3} of Te was incorporated. The carrier concentration measured in n type samples increases as the temperature is lowered. This is explained by the presence of second band close to the conduction band minima. Silane which is a common n type dopant in GaAs and other III-V systems is shown to behave like p type in GaInSb. P-n junction structures have been grown on GaSb substrates to fabricate TPV cells.

Ehsani, H.; Bhat, I.; Hitchcock, C.; Borrego, J.; Gutmann, R. [Rensselaer Polytechnic Inst., Troy, NY (United States)

1995-07-01

364

Large-area tungsten diselenide atomic layers on an insulator substrate grown by vapor phase chemical deposition  

NASA Astrophysics Data System (ADS)

Group IV transition metal dichalcogenides such as WS2 and WSe2 are one of attracting material classes which have a physical two dimension of one atomic layer and atomically thin layers like graphene. These materials have interesting features such as an indirect bulk gap makes a transition to a direct band gap in monolayer. Recent research results of FETs showed that a high effective hole mobility of 250 cm^2 /V s with subthreshold swing of 60 mV/dec from an exfoliated monolayer. Indeed it is natural to think that artificial large area synthesis is needed for practical applications. Here we report the large-area tungsten diselenide layers on SiO2 substrate using vapor phase deposition method. Selenium source was evaporated from certain distances to a tungsten thin film on SiO2/Si wafer. Nitrogen gas was flowed during all processes as a carrier gas. Growth was performed at 700 ˜ 900 Celsius degree. The size of atomic tungsten diselenide layers simply depends on a wafer and quartz tube size. Good qualities of selected tungsten diselenide layers were investigated by AFM/EFM, SEM/TEM, and Raman spectroscopy. FET and PL data also will be presented.

Yoo, Kwonjae; Kang, Il-Suk; Park, Yehoon; Ahn, Chi Won; Shin, Jongwoo; Yool Jung, Dae; Cho, Byung Jin; Choi, Sung-Yool; Choi, Hongkyw

2013-03-01

365

Electrical Properties of Halogen-Doped CdTe Layers on Si Substrates Grown by Metalorganic Vapor-Phase Epitaxy  

NASA Astrophysics Data System (ADS)

Electrical properties of halogen-doped CdTe layers grown on Si substrates using iodine and chlorine dopants are presented. No change in electrical properties of the layers was observed with chlorine as a dopant. However, doping with iodine resulted in highly conductive n-type layers or highly resistive p-type layers depending upon the growth conditions, even though a similar amount of dopant was introduced into the growth chamber. Layers grown at 560°C, with a vapor-phase Te/Cd precursor ratio of 3.0, were p-type. The resistivity of the layers remained unchanged for low dopant supply rates, but increased abruptly when the dopant supply rate was increased beyond a certain value. On the other hand, layers grown at 325°C with Te/Cd ratios from 0.1 to 0.25 were n-type. A maximum free electron concentration of 1.3 × 1017 cm-3 was obtained at room temperature. The types and conductivities of the grown layers were strongly dependent on the growth conditions.

Yasuda, K.; Niraula, M.; Oka, H.; Yoneyama, T.; Matsumoto, K.; Nakashima, H.; Nakanishi, T.; Katoh, D.; Agata, Y.

2010-07-01

366

Structural and optical properties of ?-phase tris(8-hydroxyquinoline) aluminum crystals prepared by using physical vapor deposition method  

NASA Astrophysics Data System (ADS)

Crystals of ?-phase tris(8-hydroxyquinoline) aluminum (?-Alq3) were prepared by using physical vapor deposition (PVD) method in a double zone tube furnace. The structural properties of the ?-Alq3 crystals were investigated by using an X-ray single crystal diffractometer (XSCD) and a high resolution scanning electron microscope (SEM). Large straight steps were observed from the side face of the pine needle-like crystals. The straight steps are parallel with each other like terraces and the widths of the steps are fixed, indicating that the ?-Alq3 crystals may have layered structures. The photoluminescence (PL) spectra at different temperatures (7 K, 66 K, 220 K, 300 K and 350 K) and the absorption spectrum were also investigated. The optical band gap of the ?-Alq3 crystals was calculated to be about 2.82 eV. This value is a little larger than that of amorphous mer-Alq3 (about 2.7 eV), indicating a minimizing of impurities, grain boundaries and defects.

Xie, Wanfeng; Pang, Zhiyong; Zhao, Yu; Jiang, Feng; Yuan, Huimin; Song, Hui; Han, Shenghao

2014-10-01

367

Vapor-phase atomic-controllable growth of amorphous Li2S for high-performance lithium-sulfur batteries.  

PubMed

Lithium-sulfur (Li-S) batteries hold great promise to meet the formidable energy storage requirements of future electrical vehicles but are prohibited from practical implementation by their severe capacity fading and the risks imposed by Li metal anodes. Nanoscale Li(2)S offers the possibility to overcome these challenges, but no synthetic technique exists for fine-tailoring Li(2)S at the nanoscale. Herein we report a vapor-phase atomic layer deposition (ALD) method for the atomic-scale-controllable synthesis of Li(2)S. Besides a comprehensive investigation of the ALD Li(2)S growth mechanism, we further describe the high performance of the resulting amorphous Li(2)S nanofilms as cathodes in Li-S batteries, achieving a stable capacity of ? 800 mA · h/g, nearly 100% Coulombic efficiency, and excellent rate capability. Nanoscale Li(2)S holds great potential for both bulk-type and thin-film high-energy Li-S batteries. PMID:25321606

Meng, Xiangbo; Comstock, David J; Fister, Timothy T; Elam, Jeffrey W

2014-10-28

368

Metal-Organic Vapor Phase Epitaxy Growth of Embedded Gallium Nitride Nanocolumn for Reduction in Dislocation Density  

NASA Astrophysics Data System (ADS)

The use of nanocolumn crystals is thought to be effective in producing a low-dislocation-density GaN layers. In this paper, we propose a metal-organic vapor phase epitaxial (MOVPE) growth method for producing uniform GaN nanocolumns using deep through-holes in a thick SiO2 selective growth mask. A SiO2 film with a thickness of 500 nm was deposited by sputtering on an AlN buffer layer/SiC substrate. A nanoimprinting technique was applied to produce dot openings. Then, dry etching with CF4 gas was carried out to form deep through-holes in the SiO2 film. In the second MOVPE growth, individual GaN nanocolumns coalesced into a planarized GaN layer, after thinning the SiO2 mask to 100 nm. A cathode-luminescence image of the GaN layer on a GaN nanocolumn template shows a low dislocation density of 1.3×108 cm-2, while that of a GaN layer directly grown on an AlN buffer layer shows a dislocation density of 9.4×108 cm-2.

Umeda, Shinya; Kato, Takahiro; Kitano, Tsukasa; Kondo, Toshiyuki; Matsubara, Hiroyuki; Kamiyama, Satoshi; Takeuchi, Tetsuya; Iwaya, Motoaki; Akasaki, Isamu

2013-08-01

369

Record high-aspect-ratio GaAs nano-grating lines grown by Hydride Vapor Phase Epitaxy (HVPE)  

NASA Astrophysics Data System (ADS)

Nanometric-width GaAs grating lines showing high aspect (height/width) ratio of up to 30, without roughness or shape deviation are reported. They were obtained by HVPE, capitalizing on the near-equilibrium nature of this epitaxial technique. HVPE rapid decomposition of GaCl growth precursors leads to immediate reactivity of the growth reaction to an increase or decrease of the supersaturation of the vapor phase. HVPE growth is also governed by surface kinetics: the morphologies are controlled by the intrinsic growth anisotropy of the crystals. By manipulating surface kinetics and exploiting the fast reactivity of the system, it is demonstrated that HVPE allows to benefit from an enhanced growth anisotropy favoring vertical growth of nanometer-scale grating lines. Unique high-aspect ratios are obtained in one-step short growth time (20 min), capitalizing upon the main advantage of the bottom-up approach: the structures are defined by their crystalline properties with no scattering defects as typically introduced by techniques involving dry etching. The role of surface kinetics and mass transport at the nanometer scale is discussed.

Gil, E.; André, Y.; Ramdani, M. R.; Fontaine, C.; Trassoudaine, A.; Castelluci, D.

2013-10-01

370

Impact of thermal annealing on bulk InGaAsSbN materials grown by metalorganic vapor phase epitaxy  

SciTech Connect

Two different thermal annealing techniques (rapid thermal annealing (RTA) and in-situ post-growth annealing in the metalorganic vapor phase epitaxy (MOVPE) chamber) were employed to investigate their impact on the optical characteristics of double-heterostructures (DH) of InGaAsSbN/GaAs and on the performance of single-junction solar cell structures, all grown by MOVPE. We find that an optimized RTA procedure leads to a similar improvement in the photoluminescence (PL) intensity compared with material employing a multi-step optimized anneal within the MOVPE reactor. Time-resolved photoluminescence techniques at low temperature (LT) and room temperature (RT) were performed to characterize the carrier dynamics in bulk InGaAsSbN layers. Room temperature carrier lifetimes were found to be similar for both annealing methods, although the LT-PL (16?K) measurements of the MOVPE-annealed sample found longer lifetimes than the RTA-annealed sample (680?ps vs. 260?ps) for the PL measurement energy of 1.24?eV. InGaAsSbN-based single junction solar cells processed with the optimized RTA procedure exhibited an enhancement of the electrical performance, such as improvements in open circuit voltage, short circuit current, fill factor, and efficiency over solar cells subjected to the in-situ MOVPE annealing technique.

Kim, T. W.; Mawst, L. J., E-mail: mawst@engr.wisc.edu [Department of Electrical and Computer Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Kim, K.; Lee, J. J. [Department of Electrical and Computer Engineering, Ajou University, Suwon 443-749 (Korea, Republic of); Kuech, T. F. [Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Wells, N. P.; LaLumondiere, S. D.; Sin, Y.; Lotshaw, W. T.; Moss, S. C. [Electronics and Photonics Lab, The Aerospace Corporation, El Segundo, California 90245 (United States)

2014-02-03

371

Boron Nitride Thin Films Grown on Graphitized 6H-SiC Substrates by Metalorganic Vapor Phase Epitaxy  

NASA Astrophysics Data System (ADS)

The growth of thin boron nitride (BN) films on graphitized 6H-SiC substrates was investigated in an attempt to reduce the large lattice mismatch between 6H-SiC and BN, which would improve the three-dimensional ordering in BN thin films grown by metalorganic vapor phase epitaxy (MOVPE). BN thin films were grown by low-pressure (300 Torr) MOVPE using triethylboron and ammonia on graphitized 6H-SiC substrates with surfaces displaying (1× 1) reconstruction as determined by low energy electron diffraction (LEED). The (1× 1) surfaces were formed by annealing at 1500 °C in ultrahigh vacuum with a base pressure of 10-10 Torr. The LEED patterns showed that the surfaces were covered with single-crystal graphite several monolayers thick. X-ray diffraction revealed that the c-axis lattice constant of the BN was 6.72 Å, which is close to the 6.66 Å of bulk hexagonal BN. In contrast, BN films grown on non-graphitized 6H-SiC substrates by MOVPE under the same conditions were mostly amorphous. Use of a graphitized 6H-SiC substrate covered with graphite several monolayers thick improves the degree of three-dimensional ordering in BN thin films grown by MOVPE.

Kobayashi, Yasuyuki; Hibino, Hiroki; Nakamura, Tomohiro; Akasaka, Tetsuya; Makimoto, Toshiki; Matsumoto, Nobuo

2007-04-01

372

Structural properties of phase-change InSbTe thin films grown at a low temperature by metalorganic chemical vapor deposition.  

PubMed

The feasibility of new InSbTe (IST) chalcogenide materials at the deposition temperatures of 225 and 250 degrees C using metalorganic chemical vapor deposition (MOCVD) for phase-change random access memory (PRAM) applications was investigated. Samples grown at 225 degrees C consisted of the main InTe phase, including a small amount of Sb. On the other hand, samples grown at 250 degrees C included the crystalline phases of InSb and InSbTe. MOCVD-IST materials are powerful candidates for highly-integrated PRAM applications. PMID:21446425

Ahn, Jun-Ku; Park, Kyoung-Woo; Hur, Sung-Gi; Kim, Chung-Soo; Lee, Jeong-Yong; Yoon, Soon-Gil

2011-01-01

373

Thermodynamic Properties of Nitrogen Including Liquid and Vapor Phases from 63K to 2000K with Pressures to 10,000 Bar  

NASA Technical Reports Server (NTRS)

Tables of thermodynamic properties of nitrogen are presented for the liquid and vapor phases for temperatures from the freezing line to 2000K and pressures to 10,000 bar. The tables include values of density, internal energy, enthalpy, entropy, isochoric heat capacity, isobaric heat capacity velocity of sound, the isotherm derivative, and the isochor derivative. The thermodynamic property tables are based on an equation of state, P=P (p,T), which accurately represents liquid and gaseous nitrogen for the range of pressures and temperatures covered by the tables. Comparisons of property values calculated from the equation of state with measured values for P-p-T, heat capacity, enthalpy, latent heat, and velocity of sound are included to illustrate the agreement between the experimental data and the tables of properties presented here. The coefficients of the equation of state were determined by a weighted least squares fit to selected P-p-T data and, simultaneously, to isochoric heat capacity data determined by corresponding states analysis from oxygen data, and to data which define the phase equilibrium criteria for the saturated liquid and the saturated vapor. The vapor pressure equation, melting curve equation, and an equation to represent the ideal gas heat capacity are also presented. Estimates of the accuracy of the equation of state, the vapor pressure equation, and the ideal gas heat capacity equation are given. The equation of state, derivatives of the equation, and the integral functions for calculating derived thermodynamic properties are included.

Jacobsen, Richard T.; Stewart, Richard B.

1973-01-01

374

Theoretical study of vapor-liquid homogeneous nucleation using stability analysis of a macroscopic phase.  

PubMed

Stability analysis is generally used to verify that the solution to phase equilibrium calculations corresponds to a stable state (minimum of the free energy). In this work, tangent plane distance analysis for stability of macroscopic mixtures is also used for analyzing the nucleation process, reconciling thus this analysis with classical nucleation theories. In the context of the revised nucleation theory, the driving force and the nucleation work are expressed as a function of the Lagrange multiplier corresponding to the mole fraction constraint from the minimization problem of stability analysis. Using a van der Waals fluid applied to a ternary mixture, Lagrange multiplier properties are illustrated. In particular, it is shown how the Lagrange multiplier value is equal to one on the binodal and spinodal curves at the same time as the driving force of nucleation vanishes on these curves. Finally, it is shown that, on the spinodal curve, the nucleation work from the revised and generalized nucleation theories are characterized by two different local minima from stability analysis, irrespective of any interfacial tension models. PMID:23061836

Carreón-Calderón, Bernardo

2012-10-14

375

Hot wire chemical vapor deposition chemistry in the gas phase and on the catalyst surface with organosilicon compounds.  

PubMed

Conspectus Hot wire chemical vapor deposition (HWCVD), also referred to as catalytic CVD (Cat-CVD), has been used to produce Si-containing thin films, nanomaterials, and functional polymer coatings that have found wide applications in microelectronic and photovoltaic devices, in automobiles, and in biotechnology. The success of HWCVD is largely due to its various advantages, including high deposition rate, low substrate temperatures, lack of plasma-induced damage, and large-area uniformity. Film growth in HWCVD is induced by reactive species generated from primary decomposition on the metal wire or from secondary reactions in the gas phase. In order to achieve a rational and efficient optimization of the process, it is essential to identify the reactive species and to understand the chemical kinetics that govern the production of these precursor species for film growth. In this Account, we report recent progress in unraveling the complex gas-phase reaction chemistry in the HWCVD growth of silicon carbide thin films using organosilicon compounds as single-source precursors. We have demonstrated that laser ionization mass spectrometry is a powerful diagnostic tool for studying the gas-phase reaction chemistry when combined with the methods of isotope labeling and chemical trapping. The four methyl-substituted silane molecules, belonging to open-chain alkylsilanes, dissociatively adsorb on W and Ta filaments to produce methyl radical and H2 molecule. Under the typical deposition pressures, with increasing number of methyl substitution, the dominant chemistry occurring in the gas phase switches from silylene/silene reactions to free-radical short chain reactions. This change in dominant reaction intermediates from silylene/silene to methyl radicals explains the observation from thin film deposition that silicon carbide films become more C-rich with a decreasing number of Si-H bonds in the four precursor molecules. In the case of cyclic monosilacyclobutanes, we have shown that ring-opening reactions play a vital role in characterizing the reaction chemistry. On the other hand, exocyclic Si-H(CH3) bond cleavages are more important in the less-puckered disilacyclobutane molecules. Metal filaments are essential in HWCVD since they serve as catalysts to decompose precursor gases to reactive species, which initiate gas-phase reaction chemistry and thin film growth. We discuss the structural changes in metal filaments when exposed to various precursor gases. Depending on the nature of the radical intermediates formed from the hot-wire decomposition and subsequent gas-phase reactions, metal silicides and carbides can be formed. Overall, study of the gas-phase reaction chemistry in HWCVD provides important knowledge of the chemical species produced prior to their deposition on a substrate surface. This helps in identifying the major contributor to alloy formation on the filament itself and the film growth, and consequently, in determining the properties of the deposited films. An integrated knowledge of the gas-phase reaction chemistry, filament alloy formation, and thin film deposition is required for an efficient deposition of high-quality thin films and nanomaterials. PMID:25586211

Shi, Yujun

2015-02-17

376

Transition between the 1 x 1 and ({radical}3 x 2{radical}3)R30{degree} surface structures of GaN in the vapor-phase environment  

SciTech Connect

Out-of-plane structures of the GaN(0001) surface in the metal-organic chemical vapor deposition (MOCVD) environment have been determined using in situ grazing-incidence X-ray scattering. The authors measured 11{bar 2}{ell} crystal truncation rod intensities at a variety of temperatures and ammonia partial pressures on both sides of the 1 x 1 to ({radical}3 x 2{radical}3)R30{degree} surface phase transition. The out-of-plane structure of the ({radical}3 x 2{radical}3)R30{degree} phase appears to be nearly independent of temperature below the transition, while the structure of the 1 x 1 phase changes increase rapidly as the phase transition is approached from above. A model for the structure of the 1 x 1 phase with a partially-occupied top Ga layer agrees well with the data. The observed temperature dependence is consistent with a simple model of the equilibrium between the vapor phase and the surface coverage of Ga and N. In addition, the authors present results on the kinetics of reconstruction domain coarsening following a quench into the ({radical}3 x 2{radical}3)R30{degree} phase field.

Munkholm, A.; Thompson, C.; Stephenson, G. B.; Eastman, J. A.; Auciello, O.; Fini, P.; Speck, J. S.; DenBaars, S. P.

2000-01-12

377

The functionalization of nanodiamonds (diamondoids) as a key parameter of their easily controlled self-assembly in micro- and nanocrystals from the vapor phase  

NASA Astrophysics Data System (ADS)

We detail herein readily accessible processes to control previously unobserved robust self-assemblies of nanodiamonds (diamondoids) in micro- and nanocrystals from their mild vapor deposition. The chemical functionalization of uniform and discernible nanodiamonds was found to be a key parameter, and depending on the type of functional group (hydroxy, fluorine, etc.) and its position on the diamondoid, the structure of the discrete deposits can vary dramatically. Thus, well-defined anisotropic structures such as rod, needle, triangle or truncated octahedron shapes can be obtained, and self-assembled edifices of sizes ranging from 20 nm to several hundred micrometers formed with conservation of a similar structure for a given diamondoid. Key thermodynamic data including sublimation enthalpy of diamondoid derivatives are reported, and the SEM of the self-assemblies coupled with EDX analyses and XRD attest the nature and purity of nanodiamond crystal deposits. This attractive method is simple and outperforms in terms of deposit quality dip-coating methods we used. This vapor phase deposition approach is expected to allow for an easy formation of diamondoid nanoobjects on different types of substrates.We detail herein readily accessible processes to control previously unobserved robust self-assemblies of nanodiamonds (diamondoids) in micro- and nanocrystals from their mild vapor deposition. The chemical functionalization of uniform and discernible nanodiamonds was found to be a key parameter, and depending on the type of functional group (hydroxy, fluorine, etc.) and its position on the diamondoid, the structure of the discrete deposits can vary dramatically. Thus, well-defined anisotropic structures such as rod, needle, triangle or truncated octahedron shapes can be obtained, and self-assembled edifices of sizes ranging from 20 nm to several hundred micrometers formed with conservation of a similar structure for a given diamondoid. Key thermodynamic data including sublimation enthalpy of diamondoid derivatives are reported, and the SEM of the self-assemblies coupled with EDX analyses and XRD attest the nature and purity of nanodiamond crystal deposits. This attractive method is simple and outperforms in terms of deposit quality dip-coating methods we used. This vapor phase deposition approach is expected to allow for an easy formation of diamondoid nanoobjects on different types of substrates. Electronic supplementary information (ESI) available: Full details of vapor pressure measurements, vapor deposition of functionalized diamondoids, apparatus (including PVD) and all characterization for all functionalized diamondoids self-assemblies investigated from vapor phases and solution dip-coating. See DOI: 10.1039/c4nr04442h

Gunawan, Maria A.; Poinsot, Didier; Domenichini, Bruno; Dirand, Céline; Chevalier, Sébastien; Fokin, Andrey A.; Schreiner, Peter R.; Hierso, Jean-Cyrille

2015-01-01

378

Hypothetical Thermodynamic Properties. Subcooled Vaporization Enthalpies and Vapor Pressures of Polyaromatic Heterocycles and Related Compounds  

E-print Network

Hypothetical Thermodynamic Properties. Subcooled Vaporization Enthalpies and Vapor Pressures The vaporization enthalpies and vapor pressures of the liqiud phase from T ) 298.15 K to T ) 500 K of a series in the literature was measured on a hydrated form. Vapor pressures and normal boiling temperatures for the liquid

Chickos, James S.

379

Recent Trends in Menthol Cigarette Use  

MedlinePLUS

... web browser. November 18, 2011 Recent Trends in Menthol Cigarette Use In Brief Although the overall rate ... continue, there is growing awareness and concern about menthol cigarette use. Recently, an advisory committee of the ...

380

Position-controlled III-V compound semiconductor nanowire solar cells by selective-area metal-organic vapor phase epitaxy.  

PubMed

We demonstrate position-controlled III-V semiconductor nanowires (NWs) by using selective-area metal-organic vapor phase epitaxy and their application to solar cells. Efficiency of 4.23% is achieved for InP core-shell NW solar cells. We form a 'flexible NW array' without a substrate, which has the advantage of saving natural resources over conventional thin film photovoltaic devices. Four junction NW solar cells with over 50% efficiency are proposed and discussed. PMID:22434437

Fukui, Takashi; Yoshimura, Masatoshi; Nakai, Eiji; Tomioka, Katsuhiro

2012-01-01

381

Microstructural properties and atomic arrangements of GaN nanorods grown on Si (1 1 1) substrates by using hydride vapor phase epitaxy  

Microsoft Academic Search

X-ray diffraction (XRD) patterns, field-emission scanning electron microscopy (FESEM) images, transmission electron microscopy (TEM) images, and selected area electron diffraction pattern (SADP) images showed that one-dimensional GaN nanorods with c-axis-oriented single-crystalline wurzite structures were grown on Si (111) substrates by using improved hydride vapor phase epitaxy. The high-resolution TEM (HRTEM) images showed that the crystallized GaN nanorods contained very few

K. H. Lee; Y. H. Kwon; S. Y. Ryu; T. W. Kang; J. H. Jung; D. U. Lee; T. W. Kim

2008-01-01

382

Highly conductive modulation doped composition graded p-AlGaN\\/(AlN)\\/GaN multiheterostructures grown by metalorganic vapor phase epitaxy  

Microsoft Academic Search

In this study, we present theoretical and experimental results regarding highly conductive modulation doped composition graded p-AlGaN\\/(AlN)\\/GaN multiheterostructures. Based on simulation results, several multiheterostructures were grown by metalorganic vapor phase epitaxy. Using high resolution x-ray diffraction and x-ray reflectometry, the abruptness of the AlGaN\\/AlN\\/GaN interfaces could be determined. Using electron holography, the energetic profile of the valence band could be

J. Hertkorn; S. B. Thapa; T. Wunderer; F. Scholz; Z. H. Wu; Q. Y. Wei; F. A. Ponce; M. A. Moram; C. J. Humphreys; C. Vierheilig; U. T. Schwarz

2009-01-01

383

High-Temperature Annealing Effect of Si in Group-V Ambient Prior to Heteroepitaxy of InAs in MetalOrganic Vapor Phase Epitaxy  

Microsoft Academic Search

We investigated the state of the Si(111) surface and its effect on InAs growth after annealing at high temperature with and without an As or P source flow in H2 ambient in metal--organic vapor phase epitaxy (MOVPE). In multi-step growth of InGaAs by micro-channel selective-area growth, perfect coverage of Si growth areas by InAs, which is grown first, by controlling

Momoko Deura; Yoshiyuki Kondo; Mitsuru Takenaka; Shinichi Takagi; Yukihiro Shimogaki; Yoshiaki Nakano; Masakazu Sugiyama

2011-01-01

384

Metal organic vapor phase epitaxy of InAsP\\/InP(001) quantum dots for 1.55 mum applications: Growth, structural, and optical properties  

Microsoft Academic Search

This contribution reports the metal organic vapor phase epitaxy of InAsP\\/InP(001) quantum dots with a voluntary V-alloying obtained owing to an additional phosphine flux during InAs quantum dot growth. The quantum dots were studied by photoluminescence and transmission electron microscopy. We show that the additional phosphine flux allows to tune quantum dot emission around 1.55 mum while improving their optical

A. Michon; R. Hostein; G. Patriarche; N. Gogneau; G. Beaudoin; A. Beveratos; I. Robert-Philip; S. Laurent; S. Sauvage; P. Boucaud; I. Sagnes

2008-01-01

385

Development of nuclear radiation detectors with energy discrimination capabilities based on thick CdTe layers grown by metalorganic vapor phase epitaxy  

Microsoft Academic Search

We report on the development of nuclear radiation detectors based on epitaxially grown thick single crystalline CdTe layers. The optimization of the CdTe growth on the GaAs substrates in a metalorganic vapor phase epitaxy resulted high-structural quality and thick CdTe layers of thickness up to 200 mum. Radiation detectors were fabricated by growing a 2-5 mum thick iodine-doped n-CdTe buffer

K. Yasuda; M. Niraula; H. Kusama; Y. Yamamoto; M. Tominaga; K. Takagi; Y. Agata; K. Suzuki

2004-01-01

386

Development of nuclear radiation detectors with energy discrimination capabilities based on thick CdTe Layers grown by metalorganic vapor phase epitaxy  

Microsoft Academic Search

We report on the development of nuclear radiation detectors based on epitaxially grown thick single crystalline CdTe layers. The optimization of the CdTe growth on the GaAs substrates in a metalorganic vapor phase epitaxy resulted high-structural quality and thick CdTe layers of thickness up to 200 ?m. Radiation detectors were fabricated in p-CdTe\\/n-CdTe\\/n+-GaAs structure, where a 2-5 ?m thick iodine-doped

K. Yasuda; M. Niraula; H. Kusama; Y. Yamamoto; M. Tominaga; K. Takagi; Y. Agata; K. Suzuki

2005-01-01

387

Mainstream smoke constituent yields and predicting relationships from a worldwide market sample of cigarette brands: ISO smoking conditions.  

PubMed

The study objective is evaluation of a benchmark approach for predicting mainstream smoke constituent machine-yields for conventional cigarette brands from worldwide markets. Results for ISO smoke yields support the validity of benchmarking when brands, for which yields are to be predicted, have design characteristics within boundaries established by the exploratory brands. Yields of ISO-method mainstream smoke constituents were generally well described by weighted least squares regression relationships with ISO tar (R2>0.80 and coefficient p values <0.05). The impact of the varied chemical composition of cigarette tobaccos from different regions on smoke constituent yields was recognized. Mainstream smoke nitrogen oxides and tobacco-specific nitrosamine (TSNA) yield prediction relationships improved by including tobacco nitrate or TSNA concentration factors in respective independent parameters. For carbon-filter brands, inclusion of a carbon factor improved the predicting relationships for several vapor-phase constituents. Relationships were validated with a subset of additional validation brands. Greater than 90% of the validation brands' smoke chemistry yields were within the 95% prediction intervals. Average differences between measured and predicted yields were generally within the range of one to two measurement standard deviations. The estimation methods proposed relate to machine-smoking conditions and are not intended to reflect the actual exposure of any given consumer to smoke constituents. PMID:15041144

Counts, M E; Hsu, F S; Laffoon, S W; Dwyer, R W; Cox, R H

2004-04-01

388

Cigarette Smoking and Inflammation  

PubMed Central

Cigarette smoke (CS) causes considerable morbidity and mortality by inducing cancer, chronic lung and vascular diseases, and oral disease. Despite the well-recognized risks associated with smoking, the habit remains unacceptably prevalent. Several toxins present in CS have immunomodulatory effects. CS also contains trace amounts of microbial cell components, including bacterial lipopolysaccharide. These and other CS constituents induce chronic inflammation at mucosal surfaces and modify host responses to exogenous antigens. The effects of CS on immunity are far-reaching and complex; both pro-inflammatory and suppressive effects may be induced. The net effect of CS on immunity depends on many variables, including the dose and type of tobacco, the route and chronicity of exposure, and the presence of other factors at the time of immune cell stimulation, such as Toll receptor ligands or other inflammatory mediators. CS impairs innate defenses against pathogens, modulates antigen presentation, and promotes autoimmunity. CS also impairs immunity in the oral cavity and promotes gingival and periodontal disease and oral cancer. The recognition of specific mechanisms by which CS affects host immunity is an important step toward elucidating mechanisms of tobacco-induced disease and may identify novel therapeutic approaches for the management of diseases that afflict smokers. Abbreviations: AP-1, activator protein-1; CD, cluster of differentiation; COPD, chronic obstructive pulmonary disease; HLA, human leukocyte antigen; IFN?, interferon gamma; IL, interleukin; LPS, lipopolysaccharide; MAPK, mitogen-activated protein kinase; NF-?B, nuclear factor kappa-B; RAGE, receptors for advanced glycation end-products; ROS, reactive oxidative species; ROR??, retinoic acid receptor-related orphan receptor transcription factor; STAT, signal transducer and activator of transcription; T-bet, T-box transcription factor; Th, T-helper; TLR, Toll-like receptors; TNF?, Tumor necrosis factor alpha; and TSLP, thymic stromal lymphopoeitin. PMID:21876032

Lee, J.; Taneja, V.; Vassallo, R.

2012-01-01

389

Quasi-heteroepitaxial growth of ?-Ga2O3 on off-angled sapphire (0 0 0 1) substrates by halide vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

We demonstrate the high-speed growth of ?-Ga2O3 quasi-heteroepilayers on off-angled sapphire (0 0 0 1) substrates by halide vapor phase epitaxy (HVPE). (2 bar 0 1) oriented ?-Ga2O3 layers were successfully grown using GaCl and O2 as source gases. The growth rate monotonically increased with increasing the partial pressures of the source gases, reaching over 250 ?m/h. This rate is over two orders of magnitude larger than those of conventional vapor phase epitaxial growth techniques such as molecular beam epitaxy or metalorganic vapor phase epitaxy. X-ray pole figure measurements indicated the presence of six in-plane rotational domains, in accordance with the substrate symmetry, plus some minor (3 1 0) domains. By the use of off-angled substrates and thick layer overgrowth, one of the in-plane orientations was strongly favored and the (3 1 0) residuals effectively suppressed, so that quasi-heteroepitaxial growth was achieved. Therefore, these results indicate the high-potential of the HVPE technique for the growth of thick and thin ?-Ga2O3 layers for the cost-effective production of ?-Ga2O3 based devices.

Oshima, Yuichi; V?llora, Encarnaci?n G.; Shimamura, Kiyoshi

2015-01-01

390

Modification and calibration of a passive air sampler for monitoring vapor and particulate phase brominated flame retardants in indoor air: application to car interiors.  

PubMed

A passive air sampler was modified to monitor both vapor and particulate phase brominated flame retardants (BFRs) in indoor air using polyurethane foam disks and glass fiber filters (GFF). Significant correlation (p < 0.01) was observed between passive (ng day(-1)) and active sampler (ng m(-3)) derived BFR concentrations in an office microenvironment (r = 0.94 and 0.89 for vapor and particulate phase BFRs, respectively). A calibration experiment was performed where concentrations of target BFRs were obtained for an office using a low volume active sampler operated over a 50 day period alongside passive samplers. The passive uptake rates of each studied BFR ranged between (0.558-1.509 ng day(-1)) and (0.448-0.579 ng day(-1)) for vapor and particulate phases, respectively. The passive entrapment of particles by the GFF was investigated using environmental scanning electron microscopy which revealed gravitational deposition of particles as the main mechanism involved. The developed sampler was applied to monitor BFR concentrations in 21 cars. Average concentrations of SigmaHBCDs, TBBP-A, and Sigmatetra-deca BDEs were 400, 3, and 2200 pg m(-3) in cabins and 400, 1, and 1600 pg m(-3) in trunks. No significant differences (p < 0.05) were observed between levels of SigmaHBCDs and Sigmatrito hexa- BDEs in cabins and trunks. However, TBBP-A, BDE-209, and SigmaPBDEs concentrations were significantly higher in vehicle cabins. PMID:20230020

Abdallah, Mohamed Abou-Elwafa; Harrad, Stuart

2010-04-15

391

Review article: Cigarette Smoking and Parkinson's Disease  

Microsoft Academic Search

This is a review on cigarette smoking and Parkinson's disease (PD). The relationship between cigarette smoking and Parkinson's disease is very controversial. Cigarette smoking is an established risk factor for various diseases such as lung cancer, COPD and heart disease. However, beneficial effects have been debated over the years. It was in the late 1950's that studies reported a negative

Leah R. Miller; Salil K. Das

392

Cigarette smoking in long-term schizophrenia  

Microsoft Academic Search

Purpose. – Cigarette smoking is a great health problem and prevalent among subjects with schizophrenia. Our aim was to investigate the prevalence and associations of cigarette smoking in patients with long-term schizophrenia.Methods. – Seven hundred and sixty schizophrenia patients were interviewed and their cigarette smoking was recorded.Results. – Smoking was more prevalent men than in women patients. In logistic regression

R. K. R. Salokangas; T. Honkonen; E. Stengård; A.-M. Koivisto; J. Hietala

2006-01-01

393

Electronic cigarettes and nicotine clinical pharmacology  

PubMed Central

Objective To review the available literature evaluating electronic cigarette (e-cigarette) nicotine clinical pharmacology in order to understand the potential impact of e-cigarettes on individual users, nicotine dependence and public health. Methods Literature searches were conducted between 1 October 2012 and 30 September 2013 using key terms in five electronic databases. Studies were included in the review if they were in English and publicly available; non-clinical studies, conference abstracts and studies exclusively measuring nicotine content in e-cigarette cartridges were excluded from the review. Results Nicotine yields from automated smoking machines suggest that e-cigarettes deliver less nicotine per puff than traditional cigarettes, and clinical studies indicate that e-cigarettes deliver only modest nicotine concentrations to the inexperienced e-cigarette user. However, current e-cigarette smokers are able to achieve systemic nicotine and/or cotinine concentrations similar to those produced from traditional cigarettes. Therefore, user experience is critically important for nicotine exposure, and may contribute to the products’ ability to support and maintain nicotine dependence. Conclusions Knowledge about e-cigarette nicotine pharmacology remains limited. Because a user's e-cigarette experience may significantly impact nicotine delivery, future nicotine pharmacokinetic and pharmacodynamic studies should be conducted in experienced users to accurately assess the products’ impact on public health. PMID:24732160

Schroeder, Megan J; Hoffman, Allison C

2014-01-01

394

27 CFR 40.351 - Cigarette papers.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Cigarette papers. 40.351 Section 40.351 Alcohol...MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.351...

2010-04-01

395

Cigarette smoke and lung cancer  

SciTech Connect

Cigarette smoke has been implicated in a causal relationship with carcinoma of the lung. An intriguing feature of the disease is the site-selectivity with which bronchogenic cancer manifests itself; most cancers are detected in the main, lobar and segmental bronchi, perhaps specifically at airway bifurcations. The elevated risk of lung cancer to smokers may result from a complex interplay between smoking and exposure to ambient Rn progeny, including the promotional-effect role (as opposed to being the initiating event) of cigarette smoke in tumor development. It has been determined that smokers exposed to average indoor Rn progency levels receive surprisingly high doses at hot spots within bronchial bifurcations.

Martonen, T.B.; Hofmann, W.; Lowe, J.E.

1987-01-01

396

Reducing the addictiveness of cigarettes  

PubMed Central

OBJECTIVE—To assess the feasibility of reducing tobacco-caused disease by gradually removing nicotine from cigarettes until they would not be effective causes of nicotine addiction.?DATA SOURCES—Issues posed by such an approach, and potential solutions, were identified from analysis of literature published by the US Food and Drug Administration (FDA) in its 1996 Tobacco Rule, comments of the tobacco industry and other institutions and individuals on the rule, review of the reference lists of relevant journal articles, other government publications, and presentations made at scientific conferences.?DATA SYNTHESIS—The role of nicotine in causing and sustaining tobacco use was evaluated to project the impact of a nicotine reduction strategy on initiation and maintenance of, and relapse to, tobacco use. A range of potential concerns and barriers was addressed, including the technical feasibility of reducing cigarette nicotine content to non-addictive levels, the possibility that compensatory smoking would reduce potential health benefits, and whether such an approach would foster illicit ("black market") tobacco sales. Education, treatment, and research needs to enable a nicotine reduction strategy were also addressed. The Council on Scientific Affairs came to the following conclusions: (a) gradually eliminating nicotine from cigarettes is technically feasible; (b) a nicotine reduction strategy holds great promise in preventing adolescent tobacco addiction and assisting the millions of current cigarette smokers in their efforts to quit using tobacco products; (c) potential problems such as compensatory over-smoking of denicotinised cigarettes and black market sales could be minimised by providing alternate forms of nicotine delivery with less or little risk to health, as part of expanded access to treatment; and (d) such a strategy would need to be accompanied by relevant research and increased efforts to educate consumers and health professionals about tobacco and health.?CONCLUSIONS—The council recommends the following: (a) that cessation of tobacco use should be the goal for all tobacco users; (b) that the American Medical Association continue to support FDA authority over tobacco products, and FDA classification of nicotine as a drug and tobacco products as drug-delivery devices; (c) that research be encouraged on cigarette modifications that may result in less addicting cigarettes; (d) that the FDA require that the addictiveness of cigarettes be reduced within 5-10 years; (e) expanded surveillance to monitor trends in the use of tobacco products and other nicotine-containing products; (f) expanded access to smoking cessation treatment, and strengthening of the treatment infrastructure; and (g) more accurate labelling of tobacco products, including a more meaningful and understandable indication of nicotine content.???Keywords: American Medical Association; addiction; nicotine; smoking cessation PMID:9825424

Henningfield, J.; Benowitz, N.; Slade, J.; Houston, T.; Davis, R.; Deitchman, S.

1998-01-01

397

Are all cigarettes just the same? Female's perceptions of slim, coloured, aromatized and capsule cigarettes.  

PubMed

Twelve focus groups in Glasgow (Scotland) were conducted with female non-smokers and occasional smokers aged 12-24 years (N = 75), with each group shown 11 cigarettes: two (standard) cigarettes with cork filters; two coloured cigarettes (pink or brown); four slim cigarettes; an aromatized black cigarette; a menthol cigarette and a cigarette with a flavour-changing rupturable capsule in the filter. Participants were asked to rank the cigarettes by appeal, taste and harm. The capsule cigarette was then discussed in depth. The pink coloured cigarette and slim cigarettes created significant interest and were generally perceived as most appealing and pleasant tasting, and least harmful. The black aromatized cigarette received a mixed response, with some disliking the dark colour and associating it with low appeal, strong taste and increased harm, whereas for others the smell helped to enhance appeal and taste perceptions and lower perceptions of harm. The novel capsule cigarette, when discussed in-depth, was viewed very positively. Just as research shows that cigarette packs can influence perceptions of appeal, harm and taste, this study suggests that the actual cigarettes can do likewise. The findings have implications for tobacco education and policy. PMID:25341674

Moodie, Crawford; Ford, Allison; Mackintosh, Anne; Purves, Richard

2015-02-01

398

New phase equilibrium analyzer for determination of the vapor-liquid equilibrium of carbon dioxide and permanent gas mixtures for carbon capture and storage  

NASA Astrophysics Data System (ADS)

A high-pressure, phase equilibrium analyzer incorporating a fiber-optic reflectometer is described. The analyzer has been designed for measuring the vapor-liquid equilibrium data of multi-component mixtures of carbon dioxide and permanent gases, providing a novel tool to acquire of a large number of phase equilibrium data for the development of the new carbon capture and storage technologies. We demonstrate that the analyzer is suitable for determining both the bubble- and dew-point lines at temperature from 253 K and pressure up to 25 MPa using pure CO2 and two binary mixtures of CO2 + N2 and CO2 + H2.

Ke, Jie; Parrott, Andrew J.; Sanchez-Vicente, Yolanda; Fields, Peter; Wilson, Richard; Drage, Trevor C.; Poliakoff, Martyn; George, Michael W.

2014-08-01

399

New phase equilibrium analyzer for determination of the vapor-liquid equilibrium of carbon dioxide and permanent gas mixtures for carbon capture and storage.  

PubMed

A high-pressure, phase equilibrium analyzer incorporating a fiber-optic reflectometer is described. The analyzer has been designed for measuring the vapor-liquid equilibrium data of multi-component mixtures of carbon dioxide and permanent gases, providing a novel tool to acquire of a large number of phase equilibrium data for the development of the new carbon capture and storage technologies. We demonstrate that the analyzer is suitable for determining both the bubble- and dew-point lines at temperature from 253 K and pressure up to 25?MPa using pure CO2 and two binary mixtures of CO2 + N2 and CO2 + H2. PMID:25173315

Ke, Jie; Parrott, Andrew J; Sanchez-Vicente, Yolanda; Fields, Peter; Wilson, Richard; Drage, Trevor C; Poliakoff, Martyn; George, Michael W

2014-08-01

400

Acetyl Radical Generation in Cigarette Smoke: Quantification and Simulations.  

PubMed

Free radicals are present in cigarette smoke and can have a negative effect on human health. However, little is known about their formation mechanisms. Acetyl radicals were quantified in tobacco smoke and mechanisms for their generation were investigated by computer simulations. Acetyl radicals were trapped from the gas phase using 3-amino-2, 2, 5, 5-tetramethyl-proxyl (3AP) on solid support to form stable 3AP adducts for later analysis by high performance liquid chromatography (HPLC), mass spectrometry/tandem mass spectrometry (MS-MS/MS) and liquid chromatography-mass spectrometry (LC-MS). Simulations were performed using the Master Chemical Mechanism (MCM). A range of 10-150 nmol/cigarette of acetyl radical was measured from gas phase tobacco smoke of both commerial and research cigarettes under several different smoking conditions. More radicals were detected from the puff smoking method compared to continuous flow sampling. Approximately twice as many acetyl radicals were trapped when a glass filber particle filter (GF/F specifications) was placed before the trapping zone. Simulations showed that NO/NO2 reacts with isoprene, initiating chain reactions to produce hydroxyl radical, which abstracts hydrogen from acealdehyde to generate acetyl radical. These mechanisms can account for the full amount of acetyl radical detected experimentally from cigarette smoke. Similar mechanisms may generate radicals in second hand smoke. PMID:25253993

Hu, Na; Green, Sarah A

2014-10-01

401

Determination of Carbon Dioxide, Carbon Monoxide, and Methane Concentrations in Cigarette Smoke by Fourier Transform Infrared Spectroscopy  

ERIC Educational Resources Information Center

The integrated absorbance areas of vibrational bands of CO[subscript 2], CO, and CH[subscript 4] gases in cigarette smoke were measured from Fourier transform infrared (FTIR) spectra to derive the partial pressures of these gases at different smoke times. The quantity of the three gas-phase components of cigarette smoke at different smoke times…

Tan, T. L.; Lebron, G. B.

2012-01-01

402

The lingering question of menthol in cigarettes.  

PubMed

Tobacco use is the single most important preventable cause of cancer-related deaths in the USA and many parts of the world. There is growing evidence that menthol cigarettes are starter tobacco products for children, adolescents, and young adults. Accumulating research also suggests that smoking menthol cigarettes reinforces nicotine dependence, impedes cessation, and promotes relapse. However, menthol cigarettes are exempt from the US Food and Drug Administration ban on flavored cigarettes due, in part, to the lack of empirical evidence describing the health consequences of smoking menthol cigarettes relative to regular cigarettes. Determining the biological effects of menthol cigarette smoke relative to regular cigarette smoke can clarify the health risks associated with the use of respective products and assist regulatory agencies in making scientifically based decisions on the development and evaluation of regulations on tobacco products to protect public health and to reduce tobacco use by minors. We highlight the inherent shortcomings of the conventional epidemiologic, clinical, and laboratory research on menthol cigarettes that have contributed to the ongoing debate on the public health impact of menthol in cigarettes. In addition, we provide perspectives on how future investigations exploiting state-of-the-art biomarkers of exposure and disease states can help answer the lingering question of menthol in cigarettes. PMID:25416451

Besaratinia, Ahmad; Tommasi, Stella

2015-02-01

403

Carbonyl Compounds Generated from Electronic Cigarettes  

PubMed Central

Electronic cigarettes (e-cigarettes) are advertised as being safer than tobacco cigarettes products as the chemical compounds inhaled from e-cigarettes are believed to be fewer and less toxic than those from tobacco cigarettes. Therefore, continuous careful monitoring and risk management of e-cigarettes should be implemented, with the aim of protecting and promoting public health worldwide. Moreover, basic scientific data are required for the regulation of e-cigarette. To date, there have been reports of many hazardous chemical compounds generated from e-cigarettes, particularly carbonyl compounds such as formaldehyde, acetaldehyde, acrolein, and glyoxal, which are often found in e-cigarette aerosols. These carbonyl compounds are incidentally generated by the oxidation of e-liquid (liquid in e-cigarette; glycerol and glycols) when the liquid comes in contact with the heated nichrome wire. The compositions and concentrations of these compounds vary depending on the type of e-liquid and the battery voltage. In some cases, extremely high concentrations of these carbonyl compounds are generated, and may contribute to various health effects. Suppliers, risk management organizations, and users of e-cigarettes should be aware of this phenomenon. PMID:25353061

Bekki, Kanae; Uchiyama, Shigehisa; Ohta, Kazushi; Inaba, Yohei; Nakagome, Hideki; Kunugita, Naoki

2014-01-01

404

E-cigarettes and cancer patients.  

PubMed

The increasing popularity and availability of electronic cigarettes (i.e., e-cigarettes) in many countries have promoted debate among health professionals as to what to recommend to their patients who might be struggling to stop smoking or asking about e-cigarettes. In the absence of evidence-based guidelines for using e-cigarettes for smoking cessation, some health professionals have urged caution about recommending them due to the limited evidence of their safety and efficacy, while others have argued that e-cigarettes are obviously a better alternative to continued cigarette smoking and should be encouraged. The leadership of the International Association for the Study of Lung Cancer asked the Tobacco Control and Smoking Cessation Committee to formulate a statement on the use of e-cigarettes by cancer patients to help guide clinical practice. Below is this statement, which we will update periodically as new evidence becomes available. PMID:24736063

Cummings, K Michael; Dresler, Carolyn M; Field, John K; Fox, Jesme; Gritz, Ellen R; Hanna, Nasser H; Ikeda, Norihiko; Jassem, Jacek; Mulshine, James L; Peters, Matthew J; Yamaguchi, Nise H; Warren, Graham; Zhou, Caicun

2014-04-01

405

Functional analysis and treatment of cigarette pica.  

PubMed Central

A series of analyses was conducted to assess and treat the pica of cigarette butts by a young man with mental retardation and autism. First, we demonstrated that pica was maintained in a condition with no social consequences when the available cigarettes contained nicotine but not when the cigarettes contained herbs without nicotine. Second, a choice assessment (Fisher et al., 1992) confirmed that tobacco was preferred over the other components of the cigarette (e.g., paper, filter, etc.). Third, an analogue functional analysis (Iwata, Dorsey, Slifer, Bauman & Richman, 1982/1994) demonstrated that cigarette pica was maintained independent of social consequences. Fourth, a treatment designed to interrupt the hypothesized response-reinforcer relationship reduced consumption of cigarettes to zero. Finally, because cigarette pica occurred primarily when the individual was alone or under minimal supervision, a procedure based on stimulus control was developed to improve the effectiveness of the intervention in these situations. PMID:8995829

Piazza, C C; Hanley, G P; Fisher, W W

1996-01-01

406

CIGARETTE SMOKE AND LUNG CANCER  

EPA Science Inventory

Cigarette smoke has been implicated in a causal relationship with carcinoma of the lung. An intriguing feature of the disease is the site-selectivity with which bronchogenic cancer manifests itself; most cancers are detected in the main, lobar and segmental bronchi, perhaps speci...

407

The electronic cigarette: the new cigarette of the 21st century?*  

PubMed Central

The electronic nicotine delivery system, also known as the electronic cigarette, is generating considerable controversy, not only in the general population but also among health professionals. Smokers the world over have been increasingly using electronic cigarettes as an aid to smoking cessation and as a substitute for conventional cigarettes. There are few available data regarding the safety of electronic cigarettes. There is as yet no evidence that electronic cigarettes are effective in treating nicotine addiction. Some smokers have reported using electronic cigarettes for over a year, often combined with conventional cigarettes, thus prolonging nicotine addiction. In addition, the increasing use of electronic cigarettes by adolescents is a cause for concern. The objective of this study was to describe electronic cigarettes and their components, as well as to review the literature regarding their safety; their impact on smoking initiation and smoking cessation; and regulatory issues related to their use. PMID:25410845

Knorst, Marli Maria; Benedetto, Igor Gorski; Hoffmeister, Mariana Costa; Gazzana, Marcelo Basso

2014-01-01

408

The effect of carrier gas flow rate and source cell temperature on low pressure organic vapor phase deposition simulation by direct simulation Monte Carlo method  

NASA Astrophysics Data System (ADS)

The process of low pressure organic vapor phase deposition (LP-OVPD) controls the growth of amorphous organic thin films, where the source gases (Alq3 molecule, etc.) are introduced into a hot wall reactor via an injection barrel using an inert carrier gas (N2 molecule). It is possible to control well the following substrate properties such as dopant concentration, deposition rate, and thickness uniformity of the thin film. In this paper, we present LP-OVPD simulation results using direct simulation Monte Carlo-Neutrals (Particle-PLUS neutral module) which is commercial software adopting direct simulation Monte Carlo method. By estimating properly the evaporation rate with experimental vaporization enthalpies, the calculated deposition rates on the substrate agree well with the experimental results that depend on carrier gas flow rate and source cell temperature.

Wada, Takao; Ueda, Noriaki

2013-04-01

409

The effect of carrier gas flow rate and source cell temperature on low pressure organic vapor phase deposition simulation by direct simulation Monte Carlo method.  

PubMed

The process of low pressure organic vapor phase deposition (LP-OVPD) controls the growth of amorphous organic thin films, where the source gases (Alq3 molecule, etc.) are introduced into a hot wall reactor via an injection barrel using an inert carrier gas (N2 molecule). It is possible to control well the following substrate properties such as dopant concentration, deposition rate, and thickness uniformity of the thin film. In this paper, we present LP-OVPD simulation results using direct simulation Monte Carlo-Neutrals (Particle-PLUS neutral module) which is commercial software adopting direct simulation Monte Carlo method. By estimating properly the evaporation rate with experimental vaporization enthalpies, the calculated deposition rates on the substrate agree well with the experimental results that depend on carrier gas flow rate and source cell temperature. PMID:23674843

Wada, Takao; Ueda, Noriaki

2013-04-21

410

The effect of carrier gas flow rate and source cell temperature on low pressure organic vapor phase deposition simulation by direct simulation Monte Carlo method  

PubMed Central

The process of low pressure organic vapor phase deposition (LP-OVPD) controls the growth of amorphous organic thin films, where the source gases (Alq3 molecule, etc.) are introduced into a hot wall reactor via an injection barrel using an inert carrier gas (N2 molecule). It is possible to control well the following substrate properties such as dopant concentration, deposition rate, and thickness uniformity of the thin film. In this paper, we present LP-OVPD simulation results using direct simulation Monte Carlo-Neutrals (Particle-PLUS neutral module) which is commercial software adopting direct simulation Monte Carlo method. By estimating properly the evaporation rate with experimental vaporization enthalpies, the calculated deposition rates on the substrate agree well with the experimental results that depend on carrier gas flow rate and source cell temperature. PMID:23674843

Wada, Takao; Ueda, Noriaki

2013-01-01

411

Liquid chromatographic determination of benzo(a)pyrene in total particulate matter of cigarette smoke  

SciTech Connect

The benzo(a)pyrene (BaP) delivery of reference and commercially available tobacco cigarettes, as well as reference and placebo marijuana cigarettes, is determined using a sequential liquid chromatographic/liquid chromatographic procedure. The total particulate matter of sample cigarette smoke is collected using a Cambridge filter pad, which is ultrasonically extracted with acetone. The resulting extract is filtered, then fractionated using semipreparative-scale normal phase liquid chromatography (LC). Quantitative determination is achieved using analytical-scale reverse phase LC equipped with a fluorescence detector. The method is precise (+/- 10-15% relative standard deviation) and yields 85% or better BaP recovery at the ng/cig. level. A single pad may be analyzed in 8 person-hours, while a more typical lot of 12 pads (6 pads each for 2 cigarette brands) may be analyzed in 10 person-days.

Tomkins, B.A.; Jenkins, R.A.; Griest, W.H.; Reagan, R.R.; Holladay, S.K.

1985-09-01

412

Classification of Odorants in the Vapor Phase Using Composite Features for a Portable E-Nose System  

PubMed Central

We present an effective portable e-nose system that performs well even in noisy environments. Considering the characteristics of the e-nose data, we use an image covariance matrix-based method for extracting discriminant features for vapor classification. To construct composite vectors, primitive variables of the data measured by a sensor array are rearranged. Then, composite features are extracted by utilizing the information about the statistical dependency among multiple primitive variables, and a classifier for vapor classification is designed with these composite features. Experimental results with different volatile organic compounds data show that the proposed system has better classification performance than other methods in a noisy environment. PMID:23443373

Choi, Sang-Il; Jeong, Gu-Min; Kim, Chunghoon

2012-01-01

413

Real-time acoustic sensing and control of metalorganic chemical vapor deposition precursor concentrations delivered from solid phase sources  

E-print Network

pressures of 2.5 and 0.04 Torr, respectively. An acoustic sensor was implemented on the gas feed line and closed loop control of binary gas mixture compositions delivered from low vapor pressure metalorganic to measure the concentration-dependent speed of sound in the gas mixture. This enabled sensitivity

Rubloff, Gary W.

414

AQUEOUS AND VAPOR PHASE MERCURY SORPTION BY INORGANIC OXIDE MATERIALS FUNCTIONALIZED WITH THIOLS AND POLY-THIOLS  

EPA Science Inventory

The objective of the study is the development of sorbents where the sorption sites are highly accessible for the capture of mercury from aqueous and vapor streams. Only a small fraction of the equilibrium capacity is utilized for a sorbent in applications involving short residenc...

415

Amorphous and crystalline aerosol particles interacting with water vapor - Part 1: Microstructure, phase transitions, hygroscopic growth and kinetic limitations  

Microsoft Academic Search

Interactions with water are crucial for the properties, transformation and climate effects of atmospheric aerosols. Here we outline characteristic features and differences in the interaction of amorphous and crystalline aerosol particles with water vapor. Using a hygroscopicity tandem differential mobility analyzer (H-TDMA), we performed hydration, dehydration and cyclic hydration&dehydration experiments with aerosol particles composed of levoglucosan, oxalic acid and ammonium

E. Mikhailov; S. Vlasenko; S. T. Martin; T. Koop; U. Pöschl

2009-01-01

416

Detection of the cytotoxicity of water-insoluble fraction of cigarette smoke by direct exposure to cultured cells at an air-liquid interface.  

PubMed

For the biological evaluation of cigarette smoke in vitro, the particulate phase (PP) and the gas vapor phase (GVP) of mainstream smoke have usually been collected individually and exposed to biological material such as cultured cells. Using this traditional method, the GVP is collected by bubbling in an aqueous solution such as phosphate-buffered saline (PBS). In such a way the water-insoluble GVP fraction is excluded from the GVP, meaning that the toxic potential of the water-insoluble GVP fraction has hardly been investigated so far. In our experiments we used a direct exposure method to expose cells at the air-liquid interface (ALI) to the water-insoluble GVP fraction for demonstrating its toxicological/biological activity. In order to isolate the water-insoluble GVP fraction from mainstream smoke, the GVP was passed through 6 impingers connected in series with PBS. After direct exposure of Chinese hamster ovary cells (CHO-K1) with the water-insoluble GVP fraction in the CULTEX(®) system its cytotoxicity was assayed by using the neutral red uptake assay. The water-insoluble GVP fraction was proven to be less cytotoxic than the water-soluble GVP fraction, but showed a significant effect in a dose-dependent manner. The results of this study showed that the direct exposure of cultivated cells at the air-liquid interface offers the possibility to analyze the biological and toxicological activities of all fractions of cigarette smoke including the water-insoluble GVP fraction. PMID:22999638

Nara, Hidenori; Fukano, Yasuo; Nishino, Tomoki; Aufderheide, Michaela

2013-07-01

417

Microstructural properties and atomic arrangements of GaN nanorods grown on Si (1 1 1) substrates by using hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

X-ray diffraction (XRD) patterns, field-emission scanning electron microscopy (FESEM) images, transmission electron microscopy (TEM) images, and selected area electron diffraction pattern (SADP) images showed that one-dimensional GaN nanorods with c-axis-oriented single-crystalline wurzite structures were grown on Si (1 1 1) substrates by using improved hydride vapor phase epitaxy. The high-resolution TEM (HRTEM) images showed that the crystallized GaN nanorods contained very few defects. The atomic arrangements for the GaN nanorods grown on the Si (1 1 1) substrates are described on the basis of the XRD, the TEM, the SADP, and the HRTEM results.

Lee, K. H.; Kwon, Y. H.; Ryu, S. Y.; Kang, T. W.; Jung, J. H.; Lee, D. U.; Kim, T. W.

2008-06-01

418

Suppression of Crack Generation Using High-Compressive-Strain AlN\\/Sapphire Template for Hydride Vapor Phase Epitaxy of Thick AlN Film  

Microsoft Academic Search

A stress control method was proposed to suppress crack generation in the hydride vapor phase epitaxy (HVPE) of a thick AlN film on an AlN\\/sapphire template, i.e., a high-compressive-strain (HCS) AlN\\/sapphire template was employed as a substrate. The AlN films on the HCS AlN\\/sapphire template were crack-free and very smooth. However, the AlN films on the normal AlN\\/sapphire template (with

Kenichi Tsujisawa; Shinya Kishino; Da-Bing Li; Hideto Miyake; Kazumasa Hiramatsu; Tomohiko Shibata; Mitsuhiro Tanaka

2007-01-01

419

HOW DO SMOKERS RESPOND TO CIGARETTE TAXES? EVIDENCE FROM CHINA'S CIGARETTE INDUSTRY.  

PubMed

This paper examines how Chinese smokers respond to tax-driven cigarette price increases by estimating a discrete choice model of demand for differentiated products, using annual nationwide brand-level cigarette sales data in China from 2005 to 2010. We allow for substitution between different cigarette brands and also incorporate key features of rational addiction theory into the model. Results show that the average own-price elasticity of demand for cigarettes at the brand level is -0.807, and the overall price elasticity of cigarettes at the market level is -0.488 in China. We find tax-induced substitution toward low-price cigarettes as well as high-tar cigarettes and that tax hikes encourage within-class substitution more than across-class substitution. These results have important policy implications for the potential effects of cigarette taxation. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25044632

Liu, Hong; Rizzo, John A; Sun, Qi; Wu, Fang

2014-07-18

420

Tunable generation and adsorption of energetic compounds in the vapor phase at trace levels: a tool for testing and developing sensitive and selective substrates for explosive detection.  

PubMed

Among various methods for landmine detection, as well as soil and water pollution monitoring, the detection of explosive compounds in air is becoming an important and inevitable challenge for homeland security applications, due to the threatening increase in terrorist explosive bombs used against civil populations. However, in the last case, there is a crucial need for the detection of vapor phase traces or subtraces (in the ppt range or even lower). A novel and innovative generator for explosive trace vapors was designed and developed. It allowed the generation of theoretical concentrations as low as 0.24 ppq for hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in air according to Clapeyron equations. The accurate generation of explosive concentrations at subppt levels was verified for RDX and 2,4,6-trinitrotoluene (TNT) using a gas chromatograph coupled to an electron capture detector (GC-ECD). First, sensing material experiments were conducted on a nanostructured tungsten oxide. The sensing efficiency of this material determined as its adsorption capacity toward 54 ppb RDX was calculated to be five times higher than the sensing efficiency of a 54 ppb TNT vapor. The material sensing efficiency showed no dependence on the mass of material used. The results showed that the device allowed the calibration and discrimination between materials for highly sensitive and accurate sensing detection in air of low vapor pressure explosives such as TNT or RDX at subppb levels. The designed device and method showed promising features for nanosensing applications in the field of ultratrace explosive detection. The current perspectives are to decrease the testing scale and the detection levels to ppt or subppt concentration of explosives in air. PMID:20345122

Bonnot, Karine; Bernhardt, Pierre; Hassler, Dominique; Baras, Christian; Comet, Marc; Keller, Valérie; Spitzer, Denis

2010-04-15

421

[The challenge of electronic cigarettes].  

PubMed

The electronic cigarette (e-cig) is a device with a conventional cigarette shape that releases a determined dose of nicotine vapour through an electronic heating process. The nicotine cartridges vary significantly in the amount of nicotine released, even within the same brand. Not all brands admit that they contain nicotine, but this is detected in the majority of units analysed. The e-cig usually contains a propellant, such as propylene glycol, which is a lung irritant. The short-term respiratory effect of the vapour of an e-cig is similar to that caused by the smoke of a cigarette, and is a cause of broncho-restriction. The majority of brands contain glycerine and at least one case of lipoid pneumonia has been detected due to this substance. Many brands contain traces of N-nitrosamines, heavy metals, and other products that are found in conventional cigarette smoke, but in a much higher proportion. There is currently no scientific evidence available that shows it is an effective device for quitting smoking, thus it should not be pro-actively recommended for this purpose, and may interfere with the use of demonstrated scientific evidence-based treatments for quitting smoking. It may have an undesirable effect on promoting the starting of smoking in adolescents or keeping adult smokers consuming nicotine and on gestural dependency. The toxicity of the vapour is not well known, but it is known that they are not innocuous, thus they should not be used in closed public spaces. PMID:24704194

Córdoba García, Rodrigo

2014-01-01

422

Cigarette smoking and cardiovascular disease  

Microsoft Academic Search

Data on the impact of smoking on mortality indicate that 35% of smoking-related deaths are due to cardiovascular causes. Current\\u000a cigarette smoking is associated with a threefold to sixfold increase in risk of myocardial infarction and increased rates\\u000a of ischemic stroke and subarachnoid hemorrhage. Tobacco smoking has the greatest deleterious effect on peripheral arteries,\\u000a with multiple effects ranging from increased

John H. Fish III; John R. Bartholomew

2007-01-01

423

The health effects of menthol cigarettes as compared to non-menthol cigarettes  

Microsoft Academic Search

Since the 1920s, menthol has been added to cigarettes and used as a characterizing flavor. The health effects of cigarette\\u000a smoking are well documented, however the health effects of menthol cigarettes as compared to non-menthol cigarettes is less\\u000a well studied. This review discusses menthol’s effects on 1) biomarkers of tobacco smoke exposure, 2) toxicity and cellular\\u000a effects, 3) lung function

Allison C Hoffman

2011-01-01

424

Electronic cigarettes: product characterisation and design considerations  

PubMed Central

Objective To review the available evidence regarding electronic cigarette (e-cigarette) product characterisation and design features in order to understand their potential impact on individual users and on public health. Methods Systematic literature searches in 10 reference databases were conducted through October 2013. A total of 14 articles and documents and 16 patents were included in this analysis. Results Numerous disposable and reusable e-cigarette product options exist, representing wide variation in product configuration and component functionality. Common e-cigarette components include an aerosol generator, a flow sensor, a battery and a nicotine-containing solution storage area. e-cigarettes currently include many interchangeable parts, enabling users to modify the character of the delivered aerosol and, therefore, the product's ‘effectiveness’ as a nicotine delivery product. Materials in e-cigarettes may include metals, rubber and ceramics. Some materials may be aerosolised and have adverse health effects. Several studies have described significant performance variability across and within e-cigarette brands. Patent applications include novel product features designed to influence aerosol properties and e-cigarette efficiency at delivering nicotine. Conclusions Although e-cigarettes share a basic design, engineering variations and user modifications result in differences in nicotine delivery and potential product risks. e-cigarette aerosols may include harmful and potentially harmful constituents. Battery explosions and the risks of exposure to the e-liquid (especially for children) are also concerns. Additional research will enhance the current understanding of basic e-cigarette design and operation, aerosol production and processing, and functionality. A standardised e-cigarette testing regime should be developed to allow product comparisons. PMID:24732162

Brown, Christopher J; Cheng, James M

2014-01-01

425

Phase behavior of a confined nanodroplet in the grand-canonical ensemble: the reverse liquid-vapor transition  

NASA Astrophysics Data System (ADS)

The equilibrium density distribution and thermodynamic properties of a Lennard-Jones fluid confined to nanosized spherical cavities at a constant chemical potential was determined using Monte Carlo simulations. The results describe both a single cavity with semi-permeable walls as well as a collection of closed cavities formed at the constant chemical potential. The results are compared to calculations using classical density functional theory (DFT). It is found that the DFT calculations give a quantitatively accurate description of the pressure and structure of the fluid. Both theory and simulation show the presence of a 'reverse' liquid-vapor transition whereby the equilibrium state is a liquid at large volumes but becomes a vapor at small volumes.

Lutsko, James F.; Laidet, Julien; Grosfils, Patrick

2010-01-01

426

Phase behavior of a confined nanodroplet in the grand-canonical ensemble: the reverse liquid-vapor transition.  

PubMed

The equilibrium density distribution and thermodynamic properties of a Lennard-Jones fluid confined to nanosized spherical cavities at a constant chemical potential was determined using Monte Carlo simulations. The results describe both a single cavity with semi-permeable walls as well as a collection of closed cavities formed at the constant chemical potential. The results are compared to calculations using classical density functional theory (DFT). It is found that the DFT calculations give a quantitatively accurate description of the pressure and structure of the fluid. Both theory and simulation show the presence of a 'reverse' liquid-vapor transition whereby the equilibrium state is a liquid at large volumes but becomes a vapor at small volumes. PMID:21386277

Lutsko, James F; Laidet, Julien; Grosfils, Patrick

2010-01-27

427

i-Function of Electronic Cigarette: Building Social Network by Electronic Cigarette  

Microsoft Academic Search

In this paper the role of electronic cigarette (e-cigarette) is considered in context of social networking and internet based help for smoking cessation or reduction in smoking behavior. Electronic cigarette can be a good conversation starter and interaction device. Its interestingness can be used for social network building and thus using virtual communities (e.g. Face book, Twitter etc.) to exchange

Bo Li; Shafiq ur Rehman; Haibo Li

2011-01-01

428

Using Alcohol to Sell Cigarettes to Young Adults: A Content Analysis of Cigarette Advertisements  

ERIC Educational Resources Information Center

Objective: Advertising influences the health-related behaviors of college-aged individuals. Cigarette manufacturers aggressively market to young adults and may exploit their affinity for alcohol when creating advertisements designed to increase cigarettes' appeal. Internal tobacco industry documents reveal that cigarette manufacturers understood…

Belstock, Sarah A.; Connolly, Gregory N.; Carpenter, Carrie M.; Tucker, Lindsey

2008-01-01

429

Impurities in hydride gases part 2: Investigation of trace CO2 in the liquid and vapor phases of ultra-pure ammonia  

NASA Astrophysics Data System (ADS)

Ammonia (NH3) as a precursor for epitaxial nitride films is required to be free of trace oxygenated impurities, such as CO2, that have been shown to negatively affect growth processes and device performance. Carbon dioxide can react reversibly with the NH3 gas to form ammonium carbamate, NH4COONH2 (a solid with low solubility in liquid NH3) and, therefore, can be present in cylinder sources both in the free and chemically bound form. A gas chromatograph (GC)-based method has been developed to accurately quantify the total CO2 content in both vapor- and liquid-phase NH3 streams. A heated GC-sampling manifold is used to thermally decompose any NH4COONH2 present in the sample or calibration standard so that all CO2 is analyzed in its free form. Several commercial cylinder sources maintained at room temperature were analyzed by this method, and in all cases, equilibrium concentrations of <75 parts-per-billion by volume (ppbv) CO2 were present in the gas phase as long as residual liquid was present. Slightly higher concentrations were found in the liquid phase, and upon exhaustion of the liquid phase and heating, CO2 levels strongly increased to parts-per-million by volume (ppmv) levels. The excess CO2 is likely adsorbed on the cylinder walls or dispersed in the liquid as solid NH4COONH2. These results are consistent with thermodynamic calculations based on equilibrium data for the carbamate system available in the literature. To meet the purity requirements of organo-metallic vapor-phase epitaxy processes, the performance of an adsorbent-based purifier that is capable of removing residual CO2 in both free and chemically bound forms from NH3 streams is discussed.

Funke, Hans H.; Welchhans, Jon; Watanabe, Tadaharu; Torres, Robert; Houlding, Virginia H.; Raynor, Mark W.

2004-08-01

430

Development and application of a high-speed planar laser-induced fluorescence imaging system to evaluate liquid and vapor phases of sprays from a multi-hole diesel fuel injector  

NASA Astrophysics Data System (ADS)

A high-speed imaging system capable of acquiring elastic scattering images and planar laser-induced fluorescence (PLIF) images in a near-simultaneous fashion has been developed. Acquiring both elastic scattering and PLIF images enables the liquid phase to be discriminated from the vapor phase. High-speed imaging allows the temporal evolution of flow structures to be evaluated. Images of sprays from a multi-hole diesel fuel injector operating under engine-like conditions were acquired. The vapor phase images reveal intricate fluid dynamic structures that exhibit a high degree of variability, indicative of a turbulent gas jet.

Parrish, S. E.; Zink, R. J.

2013-02-01

431

Correlation between the residual stress and the density of threading dislocations in GaN layers grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

The correlation between the residual stress and the density of threading dislocations was investigated in polar GaN layers that were grown by using hydride vapor phase epitaxy (HVPE) on three different GaN templates. The first template type was GaN grown on sapphire by metal-organic vapor phase epitaxy. The second template type was a closed GaN nucleation layer grown on sapphire by HVPE. The third template type was a non-closed GaN nucleation layer grown by HVPE, which formed isolated pyramids on the sapphire surface. The residual stress was determined using the combination of micro-Raman spectroscopy and modified sin2 ? method. The interplanar spacings needed for the sin2 ? method were obtained from the reciprocal space maps that were measured using high-resolution X-ray diffraction. The density of threading dislocations was concluded from the broaden