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1

Vaporized - E-Cigarettes, Advertising, and Youth  

E-print Network

critical to ensure any FDA regulations effectively minimizeFDA to act swiftly to assert jurisdiction over e-cigarettes and to issue regulationsFDA has yet to assert jurisdiction over e-cigarettes, there is currently no federal regulation

Legacy, for Health

2014-01-01

2

Chemical hazards present in liquids and vapors of electronic cigarettes.  

PubMed

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 Although glycerol and propylene glycol were detected in all samples, these solvents had been replaced by ethylene glycol as dominant compound in five products.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

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

2014-07-01

3

E-Cigarette Vapor May Be Less Toxic Than Tobacco Smoke  

MedlinePLUS

... enable JavaScript. E-Cigarette Vapor May Be Less Toxic Than Tobacco Smoke: Study But researcher says the ... health effects, some of these metals are extremely toxic even in very low amounts," he added. Saffari ...

4

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's restrictions on the use of tobacco and smoking-related products and electronic cigarettes and vaporizers. B-containing products including, but not limited to, cigarettes, cigars, pipes, smokeless tobacco and hookahs. It also

5

Vapor phase lubrication of ceramics  

SciTech Connect

Vapor phase lubrication of ceramics under sliding wear has been extended up to 500{degrees}C, using tricresyl phosphate as the vaporized lubricant. In order to successfully lubricate ceramics, it was necessary to first activate the surface with a metal. Different methods of activating the surface have been investigated, including in-situ reaction with metal components. Continuous vapor phase lubrication of the activated ceramic reduced the coefficient of friction from 0.7 to less than 0.1, resulting in essentially no wear. The reduction in the wear rate and friction coefficient was due to a polymeric derivative of the original TCP which was formed on the high temperature surfaces. The deposit formed on the surface was analyzed using high performance liquid chromotography (HPLC). Results have suggested that it ins an organic polymer with a molecular range of 6000 to 60000 gmole/mole and an average molecular weight of approximately 30000 gmole/mole. This method of lubrication has direct application for the continuous lubrication of ceramic engines. 9 refs., 12 figs., 1 tab.

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

1994-10-01

6

Biological vapor-phase treatment  

SciTech Connect

The biological treatment of VOCs and air toxics has received increased attention in recent years. Biotreatment of air-borne 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 liquid 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. Alternatively, suspended culture biotreatment systems analogues to wet scrubbers, bubble columns, and spray chambers can also be applied to vapor-phase problems. In this study, the biological treatment of a variety of VOCs and VOC mixture using biofilters and biotrickling filters is investigated, with emphasis on the practical operating regimes of these two systems. In addition, the operating regimes and limitations of suspended culture biotreatment systems are also addressed.

Togna, A.P.; Singh, M. [ENVIROGEN, Inc., Lawrenceville, NJ (United States)

1993-12-31

7

Vapor phase heat transport systems  

NASA Astrophysics Data System (ADS)

Progress in theoretical and experimental investigations of various forms of a vapor transport system for solar space heating is described, which could also be applied to service water heating. The refrigerant is evaporated in a solar collector, which may be located on the external wall or roof of a building. The vapor is condensed in a passively discharged thermal storage unit located within the building. The condensed liquid can be returned to the collector either by a motor-driven pump or by a completely passive self-pumping mechanism in which the vapor pressure lifts the liquid from the condenser to the collector. The theoretical investigation analyzes this self-pumping scheme. Experiments in solar test cells compared the operation of both passive and active forms of the vapor system with the operation of a passive water wall. The vapor system operates as expected, with potential advantages over other passive systems in design flexibility and energy yield.

Hedstrom, J. C.; Neeper, D. A.

1985-09-01

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

A simple and rapid method for standard preparation of gas phase extract of cigarette smoke.  

PubMed

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

10

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

11

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

12

Vapor phase epitaxy of monocrystal tungsten coatings  

NASA Astrophysics Data System (ADS)

Monocrystal tungsten coatings were obtained by vapor phase epitaxy in a W-WClx-Cl system using Mo single-crystal substrate. The kinetics of the deposition process was studied in a wider temperature and pressure range. As the total pressure was 15.77 Pa, the surface kinetics controlled by the deposition process as the temperature was in the range of 1383-1503 K. When the deposition temperature was increased up to 1573 K, the control mechanism was mass transport limited. When the deposition temperature was maintained at 1673 K and the total pressure was 15.77-25.23 Pa, the deposition process was mass transport limited. When the total pressure was increased to 42.32 Pa, the control mechanism of the deposition process became surface kinetics limited. By basic treatment, namely, 'supply transport medium as required', a kinetics model predicting the tungsten coating growth rate was achieved. In the case of lower pressure for the surface kinetics-limited regime, the deposition rate was proportional to pressure. When the pressure was high, the deposition rate was proportional to the half power of pressure. As the pressure increased further, the deposition rate and pressure became kinetically irrelevant. The model predictions were in good agreement with the experimental growth rates, as further proven by the surface morphology analysis of the monocrystal tungsten coatings.

Lv, Yanwei; Yu, Xiaodong; Wang, Fuchi; Tan, Chengwen; Yang, Qifa; Zheng, Jianping; Wang, Zhendong; Cai, Hongnian

2014-02-01

13

QCM Studies of Alcohols as Vapor Phase Lubricants for MEMS  

Microsoft Academic Search

The future of nanotechnology depends in part upon the development of successful lubrication for micromachines (MEMS). Atomic Force Microscopy (AFM) research at Pennsylvania State University* has suggested alcohols such as propanol, ethanol, butanol, and pentanol to be potential vapor phase lubricants for MEMS; propanol at its vapor pressure can greatly reduce the friction on silicon dioxide surfaces. Due to the

Heather Nemetz; Jon Jones; Tonya Coffey

2006-01-01

14

VAPOR PHASE AND PARTICULATE SELENIUM IN THE MARINE ATMOSPHERE  

Microsoft Academic Search

Particulate and vapor phase significant natural vapor flux of Se from the selenium sampling was conducted in urban and sea surface and land to the atmosphere. In coastal Rhode Island, at a coastal site in laboratory studies using elevated American Samoa, aboard ship in an upwelling concentrations of inorganic selenium, Chau et area near the Peru coast, and at two

Byard W. Mosher; Robert A. Duce

1983-01-01

15

BIOREMEDIATION OF MIXED VAPOR PHASE CONTAMINANTS FROM SOILS AND GROUNDWATER  

EPA Science Inventory

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

16

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

17

Vapor core turbulence in annular two-phase flow  

SciTech Connect

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

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

1998-06-01

18

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

19

Vapor Phase Deposition Using Plasma Spray-PVD™  

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

20

Vapor-Phase Synthesis of Gallium Phosphide Nanowires  

SciTech Connect

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

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

2009-01-01

21

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

22

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

23

Fog Machines, Vapors, and Phase Diagrams  

ERIC Educational Resources Information Center

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

Vitz, Ed

2008-01-01

24

Erbium transfer to optical fiber preforms by vapor phase technique  

Microsoft Academic Search

Erbium-doped optical fibers have been manufactured with a vapor phase technique. A `hot line' has been designed and realized which allows us to fabricate low and high alumina contents fibers, to make laser sources and optical amplifiers working in the third telecommunication window.

Guiseppe Cocito; Livio Cognolato; Angelantonio Gnazzo; C. Bruschi; D. Cout

1994-01-01

25

MODELLING AND SIMULATION OF LIQUID-VAPOR PHASE TRANSITION  

E-print Network

by a wall at a fixed temperature Twall (pool boiling). When Twall increases, we switch from a nucleate boiling to a film boiling. Nucleate Boiling Film Boiling source: http://www.spaceflight.esa.int/users/fluids/TT_boilingMODELLING AND SIMULATION OF LIQUID-VAPOR PHASE TRANSITION A Boiling Crisis Study Contribution

Helluy, Philippe

26

Assessment of radionuclide vapor-phase transport in unsaturated tuff  

SciTech Connect

This report describes bounding calculations performed to investigate the possibility of radionuclide migration in a vapor phase associated with the emplacement of high-level waste canister in unsaturated tuff formations. Two potential radionuclide transport mechanisms in the vapor phase were examined: aerosol migration and convection/diffusion of volatile species. The former may have significant impact on the release of radionuclides to the accessible environment as the concentration in the aerosols will be equal to that in the ground water. A conservative analysis of air diffusion in a stagnant liquid film indicated that for all expected repository conditions, aerosol formation is not possible. The migration of volatile species was examined both in the vicinity of a waste canister and outside the thermally disturbed zone. Two-dimensional (radial) and three-dimensional (radial-vertical) coupled heat transfer-gas flow-liquid flow simulations were performed using the TOUGH computer code. The gas flow rate relative to the liquid flow rate predicted from the simulations allowed calculations of mobility ratios due to convection which led to the conclusion that, except for the immediate region near the canister, transport in the liquid phase will be dominant for radionuclides heavier than radon. Near the waste canister, iodine transport may also be important in the vapor phase. Bounding calculations for vertical mobility ratios were carried out as a function of saturation. These calculations are conservative and agree well with the two-dimensional simulations. Based on this analysis, it is clear that vapor-phase transport will not be important for radionuclides such as cesium and heavier species. Vapor transport for iodine may play a role in the overall release scenario depending on the particular repository conditions.

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

1986-11-01

27

Identification and Characterization of Chemistry of Different Radicals in Mainstream Gas- phase Cigarette Smoke by ESI-MS method  

E-print Network

We have investigated some of the free radicals in cigarette smoke. Free radicals in the gas phase, mainstream cigarette smoke have been trapped directly by using a nitroxide probe, 3- amino- 2, 2, 5, 5- tetramethyl-1- pyrrolidinyloxy (3AP) which is supported on a solid phase, derivatized by fluorescamine, and analyzed by electrospray ionization mass spectrometry (EI- MS). We have identified some specific radicals in cigarette smoke mainstream gas phase derived from nicotine, isoprene, and glucose radicals which may be produced by reactions of OH radical through H-abstraction or addition reactions. Nicotine may undergo both OH radical addition and abstraction. However nicotine shows more tendencies to react with hydrogen abstraction from methyl group on nicotine. The addition reaction of OH radical with nicotine may happen on double bond of 6 member ring of nicotine. Isoprene and glucose react with OH radical by addition and abstraction reaction, respectively. In order to confirm the results obtained for the i...

Nejad, Maryam Abili

2010-01-01

28

Electron-spin resonance study of mainstream and sidestream cigarette smoke: nature of the free radicals in gas-phase smoke and in cigarette tar.  

PubMed Central

Radicals in the gas phase of both mainstream and sidestream cigarette smoke have been studied using electron-spin resonance ESR spin-trapping techniques with alpha-phenyl-N-tert-butyl nitrone (PBN) as the spin trap. The principal radicals we trap appear to be alkoxyl radicals. Mainstream and sidestream gas-phase smoke each have about the same concentration of radicals, about 1 X 10(16) radicals per cigarette (or 5 X 10(14) per puff). These radicals are reactive, yet they appear to be remarkably long-lived: they are still spin trapped from gas-phase smoke after more than 5 min. We propose that a steady-state concentration of reactive radicals exists in gas phase cigarette smoke. We suggest that this steady state is produced by the slow oxidation of nitric oxide (present in high concentrations in smoke and relatively unreactive) to the more reactive nitrogen dioxide, followed by the reaction of nitrogen dioxide with reactive organic molecules in smoke (such as olefins and dienes). Preliminary experiments reported here support this hypothesis. Tar from both mainstream and sidestream smoke contains persistent free radicals that exhibit broad, single-line ESR spectra with g values of 2.003. The tar radical can be extracted into tert-butylbenzene and other organic solvents, and we have applied a variety of fractionation procedures to these solutions. Most of the radicals occur in the fractions that contain the phenolic tobacco leaf pigments. Treatment of alcoholic solutions of tar with base generates a new group of radicals that appear to be semiquinone radicals derived from the oxidation of the phenolic and polyphenolic species in tar. PMID:6297881

Pryor, W A; Prier, D G; Church, D F

1983-01-01

29

ACA phase calibration scheme with the ALMA water vapor radiometers  

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

30

Vapor phase lubrication of high-temperature bearings  

NASA Astrophysics Data System (ADS)

Results are presented of an experimental investigation in which a ball-on-rod tester was modified to allow tricresylphosphate (TCP) to be vaporized into a carrier gas of air and delivered into the bottom section of the rolling contact tester operated at 3200 rpm. Tests were conducted using M50 rods and M50 balls at a pressure of 3.86 GPa and a temperature of 350 C and with silicon nitride rods and balls at a contact pressure of 5.13 GPa and temperatures of 350 and 680 C. A vaporized stream of 0.5 percent TCP was used to lubricate the rod and balls for test times from 90 min to 8 hr, and a mild polishing occurred on the active bearing surfaces. SEM photographs of the vapor-lubricated surface showed a distinct tenacious deposit on the ball cage, rod, and balls. These results indicate that vapor phase lubrication can be used for high pressure bearing contacts, providing effective lubrication for temperatures up to at least 680 C.

Graham, E. E.; Nesarikar, Abhijit; Forster, Nelson; Givan, Garry

1993-09-01

31

QCM Studies of Alcohols as Vapor Phase Lubricants for MEMS  

NASA Astrophysics Data System (ADS)

The future of nanotechnology depends in part upon the development of successful lubrication for micromachines (MEMS). Atomic Force Microscopy (AFM) research at Pennsylvania State University* has suggested alcohols such as propanol, ethanol, butanol, and pentanol to be potential vapor phase lubricants for MEMS; propanol at its vapor pressure can greatly reduce the friction on silicon dioxide surfaces. Due to the relatively high vapor pressure of these alcohols, all surfaces of a MEMS, including buried interfaces not easily reached by solid coatings, should become coated in thin layers of the alcohol upon exposure. We are testing the ability of the alcohols to migrate to buried interfaces in the MEMS. The mass uptake of the alcohols will be measured using the quartz crystal microbalance (QCM) in a vacuum chamber. The resonant frequency of the QCM drops as alcohols adsorb on its face. The uptake of the alcohols is measured as the pressure increases using different geometries of the cans, allowing us to simulate a buried interface. The aforementioned alcohols are first thermally distilled, then leaked into the chamber until vapor pressure of the alcohol is reached. We see significant mass uptake even in extreme geometries, where the entire QCM face is only accessible through a tiny hole in the can encasing the QCM, 0.0006'' in diameter. *K. Strawhecker et al., Trib. Lett. 19, 17 (2005).

Nemetz, Heather; Jones, Jon; Coffey, Tonya

2006-11-01

32

Vapor-phase esterification catalyzed by decationized Y zeolites  

SciTech Connect

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

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

1983-04-01

33

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

34

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

35

Hydraulic and thermal characteristics of a vapor venting two-phase microchannel heat exchanger  

Microsoft Academic Search

In the present work we design, model and experimentally characterize a two-phase vapor venting parallel microchannel heat exchanger capped with a 220nm pore, hydrophobic PTFE membrane that vents the vapor phase into separate vapor transport channels. We compare the performances of a traditional non-venting heat exchanger and the vapor-separating version operating at heat fluxes of up to 820kW\\/m2 and water

Milnes P. David; Josef Miler; Julie E. Steinbrenner; Yizhang Yang; Maxat Touzelbaev; Kenneth E. Goodson

2011-01-01

36

Molecular Vapor Deposition - An Improved Vapor-Phase Deposition Technique of Molecular Coatings for MEMS Devices  

Microsoft Academic Search

This paper reports the results of a new surface modification technique called Molecular Vapor Deposition (MVD). The MVD technique is an enhancement of a conventional vapor deposition of ultra-thin organic molecules by incorporating an in-situ surface plasma treatment and the precise delivery of precursor vapors. Properties of the MVD coatings can be tailored and were found to exhibit superior performance

Boris Kobrin; Victor Fuentes; Srikanth Dasaradhi; Richard Yi; Romuald Nowak; Jeff Chinn; Robert Ashurst; Carlo Carraro; Roya Maboudian

2004-01-01

37

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

38

Quantitative infrared spectra of vapor phase chemical agents  

NASA Astrophysics Data System (ADS)

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

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

2003-08-01

39

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

40

Condensed-phase transitions in binary systems during dynamic vaporization experiments. Effusion and transpiration  

SciTech Connect

During a condensed-phase transition at equilibrium in a vaporization experiment, three phases are present. In this paper, equations relating vapor pressure, temperature, and compositions of the vapor and condensed phases are derived for systems undergoing such transitions. Previously observed unusual phenomena, such as vapor pressures that increase at constant temperature and vapor pressures that increase with decreasing temperature, are explained. It is shown that equilibrium condensed-phase transitions in the presence of the vapor are always hysteretic in the temperature; the transition occurs at a higher temperature in the increasing-temperature direction than in the decreasing-temperature direction. The particular cases of effusion and transpiration experiments are treated in detail. 31 refs., 5 figs.

Edwards, J.G. [Univ. of Toledo, OH (United States); Franzen, H.F. [Ames Lab., IA (United States)

1995-03-30

41

Metalorganic vapor phase growth of quantum well structures on thick metamorphic buffer layers grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

The hydride vapor phase epitaxy technique (HVPE) can deposit uniform materials at high growth rates, making it suitable for the formation of metamorphic buffer layers (MBLs). HVPE was used to form InxGa1-x As-based MBLs as substrates in the metalorganic vapor phase epitaxy (MOVPE) of superlattice (SL) structures. Samples were grown over a range of deposition temperatures and reactant flows and their effect on the ternary alloy composition and growth rate was determined. Over the compositional range of xInAs<0.4, the alloy composition varied almost linearly with indium chloride pressure (PInCl). A compositionally step-graded MBL consisting of nine intermediate steps followed by a thick, constant composition layer of xInAs˜0.23 was grown. The MBL was characterized by high-resolution x-ray diffraction (HRXRD) and reciprocal space mapping. The topmost layer was highly relaxed, exhibiting a residual strain of -0.0011±0.0002. Chemical-mechanical polishing (CMP) was used to reduce the surface cross hatching, affecting a decrease in rms roughness from 2.10 to 1.39 nm. A 20 period, In0.33Ga0.67As (3.1 nm)/Al0.90In0.10As (7.2 nm) strain-balanced superlattice (SL) structure was grown by MOVPE on the as-grown and CMP-prepared MBL and characterized by HRXRD. The diffraction pattern of the SL grown on the CMP-prepared MBL was significantly more intense with narrower x-ray diffraction peaks when compared with the SL on as-grown MBL.

Schulte, Kevin L.; Garrod, Toby J.; Wan Kim, Tae; Kirch, Jeremy; Ruder, Steven; Mawst, Luke J.; Kuech, T. F.

2013-05-01

42

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

43

Homogeneous nucleation of droplets from a supersaturated vapor phase Michael P. Moody and Phil Attard  

E-print Network

Homogeneous nucleation of droplets from a supersaturated vapor phase Michael P. Moody and Phil the homogeneous nucleation of droplets from a supersaturated vapor, beginning with a partition function state with unfavorably high supersaturation levels being maintained in the gas phase. Homogeneous

Attard, Phil

44

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

SciTech Connect

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

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

2002-11-14

45

Cigarette smoke extract increases albumin flux across pulmonary endothelium in vitro  

SciTech Connect

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

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

1989-01-01

46

A review of porous media enhanced vapor-phase diffusion mechanisms, models, and data: Does enhanced vapor-phase diffusion exist?  

SciTech Connect

A review of mechanisms, models, and data relevant to the postulated phenomenon of enhanced vapor-phase diffusion in porous media is presented. Information is obtained from literature spanning two different disciplines (soil science and engineering) to gain a diverse perspective on this topic. Findings indicate that while enhanced vapor diffusion tends to correct the discrepancies observed between past theory and experiments, no direct evidence exists to support the postulated processes causing enhanced vapor diffusion. Numerical modeling analyses of experiments representative of the two disciplines are presented in this paper to assess the sensitivity of different systems to enhanced vapor diffusion. Pore-scale modeling is also performed to evaluate the relative significance of enhanced vapor diffusion mechanisms when compared to Fickian diffusion. The results demonstrate the need for additional experiments so that more discerning analyses can be performed.

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

1996-05-01

47

Simultaneous determination of nicotine and 3-vinylpyridine in single cigarette tobacco smoke and in indoor air using direct extraction to solid phase  

PubMed Central

The aim of the present study was to develop a new analytical method of chromatographic determination of two important markers of ETS exposure: nicotine and 3-vinylpyridine (3-ethenylpyridine, 3-EP) in mainstream (MS) and sidestream (SS) smoke of one single cigarette and in indoor air using direct solid phase extraction combined with gas chromatography. The method can be utilised for both nicotine and 3-EP determination in SS and MS of one single cigarette as well as it allows for a precise determination of compound distribution in indoor air. The application of the same analytical method for both kinds of samples allows anticipating indoor air distribution of both analysed compounds in a very precise way. The precision of the method (calculated as a relative standard deviation) was 9.78% for nicotine and 2.67% for 3-EP; whereas the accuracy (evaluated by a recovery study conducted at three different levels) was 70.1 and 87.3%, respectively. The limit of detection was 0.06 µg per cigarette for both nicotine and 3-EP. The method was evaluated by determining the compounds of interest in two commercially available brands of cigarettes as well as in the reference cigarettes 3R4F and also in indoor air polluted with tobacco smoke. Determined levels of compounds of interest in MS varied from 586 to 772 (nicotine) µg per cigarette and from 3.5 to 10.7 (3-EP) µg per cigarette. In SS smoke the level varied from 14,370 to 22,590 (nicotine) µg per cigarette and from 185 to 550 (3-EP) µg per cigarette, whereas levels in indoor air polluted with tobacco smoke varied from 50.1 to 157.3 (nicotine) µg m?3 and from 7.7 to 20.8 (3-EP) µg m?3. PMID:19662106

Koszowski, Bartosz; Goniewicz, Maciej Lukasz; Czogala, Jan; Zymelka, Anna; Sobczak, Andrzej

2009-01-01

48

Non-aqueous phase liquid spreading during soil vapor extraction  

PubMed Central

Many non-aqueous phase liquids (NAPLs) are expected to spread at the air – water interface, particularly under non-equilibrium conditions. In the vadose zone, this spreading should increase the surface area for mass transfer and the efficiency of volatile NAPL recovery by soil vapor extraction (SVE). Observations of spreading on water wet surfaces led to a conceptual model of oil spreading vertically above a NAPL pool in the vadose zone. Analysis of this model predicts that spreading can enhance the SVE contaminant recovery compared to conditions where the liquid does not spread. Experiments were conducted with spreading volatile oils hexane and heptane in wet porous media and capillary tubes, where spreading was observed at the scale of centimeters. Within porous medium columns up to a meter in height containing stagnant gas, spreading was less than ten centimeters and did not contribute significantly to hexane volatilization. Water film thinning and oil film pinning may have prevented significant oil film spreading, and thus did not enhance SVE at the scale of a meter. The experiments performed indicate that volatile oil spreading at the field scale is unlikely to contribute significantly to the efficiency of SVE. PMID:14734243

Kneafsey, Timothy J.; Hunt, James R.

2010-01-01

49

Numerical Modeling of Liquid-Vapor Phase Change  

NASA Technical Reports Server (NTRS)

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

Esmaeeli, Asghar; Arpaci, Vedat S.

2001-01-01

50

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

PubMed

Optoelectronic sensing of gas phase hazardous chemicals is a newly explored field, which shows great advantages towards low concentration sensing when compared to normal gas sensing in the dark. Here, based on the recent progress on nanostructured vapor phase explosive gas sensors operated in dark conditions, the attractiveness of developing optoelectronic sensors for vapor phase explosive detection was highlighted. Furthermore, we try to propose some new insights to enhance optoelectronic sensing of vapor phase explosives. We suggest employing photocatalysis principles to enhance the sensitivity and employing a molecular imprinting technique (MIT) to enhance the selectivity. PMID:24072058

Zu, Baiyi; Guo, Yanan; Dou, Xincun

2013-11-21

51

Oriented growth of cadmium telluride crystals from the vapor phase  

Microsoft Academic Search

The effect of the temperature of crystallization, the magnitude of mass transfer, and the structure of the seed crystal on the oriented growth of cadmium telluride crystals from the vapor was studied. Crystals oriented in the <110>, <111>, and <112> directions were grown in the temperature interval 1130-1330 K from the vapor of cadmium telluride crystals. The maximum possible rates

L. A. Klinkova; S. A. Erofeeva

1988-01-01

52

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

53

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

54

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

SciTech Connect

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

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

1995-12-31

55

Effect of gas phase and particulate phase of cigarette smoke on salivary antioxidants. What can be the role of vitamin C and pyridoxine?  

PubMed

The effect of smoking is in our days a serious global public health problem of major concern. Incidence of oral squamous cell carcinoma (SCC) in cigarette smokers is four to seven times higher than in nonsmokers. There is a constant and direct attack of various cigarette smoke constituents on the oral epithelial cells, which gradually accumulate and cause malignant transformation. Saliva is the first biological fluid that encounters inhaled cigarette smoke (CS). We have studied the influence of CS on salivary antioxidant capacity, uric acid, amylase and LDH (lactate dehydrogenase). In our study both, gas and particulate phase of CS were tested separately, and possible antioxidant effect of pyridoxine on salivary components was examined. Our results indicate that exposure to both, gas and particulate phase of CS caused a statistically significant decrease in salivary uric acid, LDH and amylase activity. We have also studied the effect of vitamin C (10 mg/dl) and vitamin B6 (1 mM) during incubation of saliva in the presence of CS. The addition of vitamin C had a significant (p < 0.05) protective effect on salivary uric acid level (0.25 +/- 0.12 for saliva incubated with gas phase of CS vs. 0.65 +/- 0.12 for saliva incubated with gas phase of CS in the presence of vitamin C). Vitamin C was not able to maintain/restore the original uric acid level. In the presence of the gas phase, pyridoxine had no protective effect, neither on salivary uric acid level nor on the FRAP activity of saliva. The purpose of our study was to discover a connection between the level of antioxidants in saliva in the presence of the two components of CS. Our results show that salivary antioxidant system is significantly and distinctly affected by both gas and particulate phase of CS and suggest that an adequate intake of antioxidants may help smokers to avoid CS-induced oxidative damage and to prevent degenerative diseases. PMID:18048964

Greabu, Maria; Battino, Maurizio; Totan, Alexandra; Mohora, Maria; Mitrea, Niculina; Totan, Cosmin; Spinu, Tudor; Didilescu, Andreea

2007-01-01

56

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

SciTech Connect

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

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

1989-03-01

57

Sorption capacity of ground tires for vapor-phase volatile organic compounds  

SciTech Connect

Batch sorption tests were conducted to determine the partition coefficient of volatile organic compounds (VOCs) by ground tires. The partition coefficient in the vapor phase was estimated by dividing the partition coefficient in the aqueous phase by Henry`s law constant. Under a diluted condition VOCs are sorbed onto ground tires noncompetitively regardless of the existence of other VOCs. Polar compounds such as methylene chloride were less sorbed onto ground tires than nonpolar compounds. The vapor-phase partition coefficient was found to have a logarithmic relationship with the saturation vapor concentration. VOCs emitted from waste-water treatment facilities can be effectively retarded by the ground tires.

Kim, J.Y.; Park, J.K.; Edil, T.B. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Civil and Environmental Engineering; Jhung, J.K. [Won-Kwang Univ., Iri City (Korea, Republic of). Dept. of Urban Planning Engineering

1996-12-31

58

Cigarettes Commencemet  

E-print Network

Highlights · Cigarettes · Commencemet · Exit Test · Birthdays TheELIWeekly SERIOUS Changes Don't throw your cigarette butts (or ANYTHING) on the ground! Folks, the university is getting very, very that people do not throw their cigarette butts on the ground any longer. This is considered litter. People

Pilyugin, Sergei S.

59

Vapor Phase Acetylation of Southern Pine, Douglas-Fir, and Aspen Wood Flakes  

Microsoft Academic Search

Southern pine, Douglas-fir, and aspen wood flakes were acetylated with acetic anhydride vapor and compared with flakes acetylated with liquid acetic anhydride diluted with xylene. The rate of acetylation was much lower for the vapor than for the liquid phase reaction. Acetylation weight percent gains above 20 were achieved by both methods. Flakeboards made from both types of flakes absorbed

Roger M. Rowell

1986-01-01

60

Homogeneous nucleation of particles from the vapor phase in thermal plasma synthesis  

Microsoft Academic Search

Particle nucleation and growth are simulated for iron vapor in a thermal plasma reactor with an assumed one-dimensional flow field and decoupled chemistry and aerosol dynamics. Including both evaporation and coagulation terms in the set of cluster-balance rate equations, a sharply defined homogeneous nucleation event is calculated. Following nucleation the vapor phase is rapidly depleted by condensation, and thereafter particle

S. L. Girshick; C.-P. Chiu

1989-01-01

61

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

62

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, Vaporization and Fusion Enthalpies From  

E-print Network

Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds. Sublimation, and sublimation are included for organic, organometallic, and a few inorganic compounds. This compendium.1063/1.3309507 Key words: Vaporization enthalpy; fusion enthalpy; sublimation enthalpy; compendium. CONTENTS 1

Chickos, James S.

63

Oriented growth of cadmium telluride crystals from the vapor phase  

SciTech Connect

The effect of the temperature of crystallization, the magnitude of mass transfer, and the structure of the seed crystal on the oriented growth of cadmium telluride crystals from the vapor was studied. Crystals oriented in the <110>, <111>, and <112> directions were grown in the temperature interval 1130-1330 K from the vapor of cadmium telluride crystals. The maximum possible rates of growth of single crystals and the activation energy of the growth process in the temperature interval studied in the directions <110>, <111>, and <112> (522, 372, and 334 kJ/mole, respectively) were determined.

Klinkova, L.A.; Erofeeva, S.A.

1988-08-01

64

Speciation and quantification of vapor phases in soy biodiesel and waste cooking oil biodiesel.  

PubMed

This study characterizes the compositions of two biodiesel vapors, soy biodiesel and waste cooking oil biodiesel, to provide a comprehensive understanding of biodiesels. Vapor phases were sampled by purging oil vapors through thermal desorption tubes which were then analyzed by the thermal desorption/GC/MS system. The results show that the compounds of biodiesel vapors can be divided into four groups. They include methyl esters (the main biodiesel components), oxygenated chemicals, alkanes and alkenes, and aromatics. The first two chemical groups are only found in biodiesel vapors, not in the diesel vapor emissions. The percentages of mean concentrations for methyl esters, oxygenated chemicals, alkanes and alkenes, and aromatics are 66.1%, 22.8%, 4.8% and 6.4%, respectively for soy biodiesel, and 35.8%, 35.9%, 27.9% and 0.3%, respectively for waste cooking oil biodiesel at a temperature of 25+/-2 degrees C. These results show that biodiesels have fewer chemicals and lower concentrations in vapor phase than petroleum diesel, and the total emission rates are between one-sixteenth and one-sixth of that of diesel emission, corresponding to fuel evaporative emissions of loading losses of between 106 microg l(-1) and 283 microg l(-1). Although diesels generate more vapor phase emissions, biodiesels still generate considerable amount of vapor emissions, particularly the emissions from methyl esters and oxygenated chemicals. These two chemical groups are more reactive than alkanes and aromatics. Therefore, speciation and quantification of biodiesel vapor phases are important. PMID:16904162

Peng, Chiung-Yu; Lan, Cheng-Hang; Dai, Yu-Tung

2006-12-01

65

Electronic Cigarette Use by College Students  

PubMed Central

Background Electronic cigarettes, or ecigarettes, are battery operated devices that deliver nicotine via inhaled vapor. There is considerable controversy about the disease risk and toxicity of ecigarettes and empirical evidence on short- and long-term health effects is minimal. Limited data on e-cigarette use and correlates exist, and to our knowledge, no prevalence rates among U.S. college students have been reported. This study aimed to estimate the prevalence of ecigarette use and identify correlates of use among a large, multi-institution, random sample of college students. Methods 4,444 students from 8 colleges in North Carolina completed a Webbased survey in fall 2009. Results Ever use of ecigarettes was reported by 4.9% of students, with 1.5% reporting past month use. Correlates of ever use included male gender, Hispanic or “Other race” (compared to non-Hispanic Whites), Greek affiliation, conventional cigarette smoking and e-cigarette harm perceptions. Although e-cigarette use was more common among conventional cigarette smokers, 12% of ever e-cigarette users had never smoked a conventional cigarette. Among current cigarette smokers, e-cigarette use was negatively associated with lack of knowledge about e-cigarette harm, but was not associated with intentions to quit. Conclusions Although e-cigarette use was more common among conventional cigarette smokers, it was not exclusive to them. E-cigarette use was not associated with intentions to quit smoking among a sub-sample of conventional cigarette smokers. Unlike older, more established cigarette smokers, e-cigarette use by college students does not appear to be motivated by the desire to quit cigarette smoking. PMID:23746429

Sutfin, Erin L.; McCoy, Thomas P.; Morrell, Holly E. R.; Hoeppner, Bettina B.; Wolfson, Mark

2013-01-01

66

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

67

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...

68

Student Understanding of Liquid-Vapor Phase Equilibrium  

ERIC Educational Resources Information Center

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

Boudreaux, Andrew; Campbell, Craig

2012-01-01

69

Microwave-assisted fast vapor-phase transport synthesis of MnAPO-5 molecular sieves  

SciTech Connect

MnAPO-5 was prepared by a microwave-assisted vapor-phase transport method at 180 deg. C in short times. The products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectra, UV-vis spectroscopic measurement, NH{sub 3}-temperature-programmed desorption and esterification reaction. It was found that dry gels prepared with aluminum isopropoxide, phosphoric acid and manganese acetate could be transferred to MnAPO-5 in the vapors of triethylamine and water by the microwave-assisted vapor-phase transport method at 180 deg. C for less than 30 min. The crystallization time was greatly reduced by the microwave heating compared with the conventional heating. The resulting MnAPO-5 exhibited much smaller particle sizes, higher surface areas and slightly higher catalytic activity in the esterification of acetic acid and butyl alcohol than those prepared by the conventional vapor-phase transport method and hydrothermal synthesis.

Shao Hui [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China); Department of Chemical Engineering, Jiangsu Polytechnic University, Changzhou 213016 (China); Yao Jianfeng; Ke Xuebin [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China); Zhang Lixiong [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China)], E-mail: lixiongzhang@yahoo.com; Xu Nanping [State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009 (China)

2009-04-02

70

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

71

Irritants in cigarette smoke plumes  

SciTech Connect

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

Ayer, H.E.; Yeager, D.W.

1982-11-01

72

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

73

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

74

Effect of Molecular Rotation on Vapor Phase Nucleation: Fullerenes C60 and C70  

Microsoft Academic Search

The effect of rotational free energy of fullerenes C60 and C70 on homogeneous nucleation of crystals from vapor phase have been studied. Classical nucleation parameters have been estimated for the case of nucleation and crystal growth of C60 and C70 by Physical Vapor Transport (PVT) method under different supercooling in the range of 20–150 K, keeping the source temperatures constant.

C. Sekar; R. Dhanasekaran; C. Subramanian

1996-01-01

75

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

Microsoft Academic Search

Plasma spray-physical vapor deposition (PS-PVD) is a low pressure plasma spray technology recently developed by Sulzer Metco\\u000a AG (Switzerland). Even though it is a thermal spray process, it can deposit coatings out of the vapor phase. The basis of\\u000a PS-PVD is the low pressure plasma spraying (LPPS) technology that has been well established in industry for several years.\\u000a In comparison

Konstantin von Niessen; Malko Gindrat

2011-01-01

76

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

77

Engineering work plan for tank 241-C-103 vapor phase characterization (ECN 613188). Revision 1  

SciTech Connect

The tasks described by this work plan have been completed. The purpose of this revision it to document what actually occurred during the performance of this work plan. The scope was and is limited to phases 1 and 2 as described in the program plan, revision 1. Phases 1 and 2 include the tank 241-C-103 (C-103) vapor. For economic and as low as reasonably achievable (ALARA) reasons, we will limit our scope to characterize the C-103 vapor phase for the categories that could be expected to impact facility worker safety from a toxicological and flammability standpoint. In anticipation that a vapor treatment system may be required, categories necessary for design will also be included. It will be the intent of the C-103 vapor characterization program to: (1) identify the substances from the above list of categories that are applicable to the issues involving C-103, and (2) implement a phased plan which will develop the organic vapor phase characterization method and then characterize the organics and the other selected substances to the required quantitative certainty.

Conrad, R.B.

1994-10-05

78

Ultrafast dynamics of the acoustic vaporization of phase-change microdroplets.  

PubMed

Acoustically sensitive emulsions are a promising tool for medical applications such as localized drug delivery. The physical mechanisms underlying the ultrasound-triggered nucleation and subsequent vaporization of these phase-change emulsions are largely unexplored. Here, the acoustic vaporization of individual micron-sized perfluoropentane (PFP) droplets is studied at a nanoseconds timescale. Highly diluted emulsions of PFP-in-water and oil-in-PFP-in-water droplets, ranging from 3.5 to 11??m in radius, were prepared and the nucleation and growth of the vapor bubbles was imaged at frame rates of up to 20 Mfps. The droplet vaporization dynamics was observed to have three distinct regimes: (1) prior to nucleation, a regime of droplet deformation and oscillatory translations within the surrounding fluid along the propagation direction of the applied ultrasound; (2) a regime characterized by the rapid growth of a vapor bubble enhanced by ultrasound-driven rectified heat transfer; and (3) a final phase characterized by a relatively slow expansion, after ultrasound stops, that is fully dominated by heat transfer. A method to measure the moment of inception of the nucleation event with respect to the phase of the ultrasound wave is proposed. A simple physical model captures quantitatively all of the features of the subsequent vapor bubble growth. PMID:23927201

Shpak, Oleksandr; Kokhuis, Tom J A; Luan, Ying; Lohse, Detlef; de Jong, Nico; Fowlkes, Brian; Fabiilli, Mario; Versluis, Michel

2013-08-01

79

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

NASA Technical Reports Server (NTRS)

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

Morales, Wilfredo; Handschuh, Robert F.

1999-01-01

80

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

81

Substitutes for tobacco smoking: a behavioral economic analysis of nicotine gum, denicotinized cigarettes, and nicotine-containing cigarettes.  

PubMed

Both pharmacological and nonpharmacological stimuli may be responsible for the reinforcement and maintenance of tobacco smoking. The present study examined the self-administration of nicotine gum, denicotinized cigarettes, and nicotine-containing cigarettes utilizing a behavioral economic design in order to investigate the pharmacological and nonpharmacological aspects of cigarette smoking. Cigarette-deprived, dependent smokers worked for cigarette puffs and nicotine gum in daily operant sessions. In one phase, nicotine-containing cigarettes were available at increasing unit prices across sessions. Three phases replicated these sessions with nicotine gum, denicotinized cigarettes, or both, concurrently available at a constant unit price. As nicotine-containing cigarette unit price increased, consumption decreased. However, as nicotine-containing cigarette unit price increased, nicotine gum and denicotinized cigarette consumption increased. Consumption of nicotine gum, but not denicotinized cigarettes, diminished when all three reinforcers were concurrently available. Concurrently available denicotinized cigarettes, but not nicotine gum, caused a statistically significant reduction in nicotine-containing cigarette consumption. In another phase, denicotinized cigarettes were available at increasing unit prices across sessions while nicotine gum was concurrently available at a constant unit price. This phase demonstrated that nicotine content had no reliable effect on cigarette or nicotine gum consumption. These results suggest that denicotinized cigarettes are a more effective alternative reinforcer than nicotine gum, indicating that nonpharmacological stimuli of smoking merit attention in smoking cessation treatment. Furthermore, these findings indicate that alternative reinforcement would be most effective in smoking cessation treatment when combined with high prices for cigarettes. PMID:15194203

Johnson, Matthew W; Bickel, Warren K; Kirshenbaum, Ari P

2004-06-11

82

Experimental studies on nucleation, nanoparticle's formation and polymerization from the vapor phase  

NASA Astrophysics Data System (ADS)

This research is divided into three major parts. In part I, the critical supersaturations required for the homogeneous nucleation of 2,2,2-trifluorothanol (TFE) vapor have been measured over a temperature range (266-296 K) using an upward thermal diffusion cloud chamber (DCC). The measured supersaturations are in agreement with the predictions of both the classical and the scaled theory of nucleation. Moreover, the condensation of supersaturated TFE vapor on laser-vaporized magnesium nanoparticles has been studied under different experimental conditions, such as the supersaturation, the pressure and the electric field. In part II, the laser vaporization controlled condensation (LVCC) technique was used to prepare Au-Ag alloy nanoparticles in the vapor phase using designed targets of compressed Au and Ag micron-sized powder mixtures of selected composition. The results showed that the optical properties of these nanoparticles could be tuned depending on the alloy composition and the laser wavelength. Different intermetallic nanoparticles (FeAl and NiAl) from the vapor phase has also been prepared, using the same approach. In this work, the fraction of the charged particles generated during the laser vaporization process was used to prepare a new class of nanoparticle assemblies in the LVCC chamber under the influence of an electric field. The results showed that the electric field required to induce the formation of these nanoassemblies is material and field dependent. By coupling the LVCC chamber with the differential mobility analyzer, size-selected nanoparticles have been prepared in the vapor phase. The prepared nanoparticles were characterized by different techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-visible spectroscopy. In part III, new methods were developed to prepare nanoparticle-polymer composites from the vapor phase. In the first method, the LVCC method was used to prepare a carbonaceous cross-linked resin, with different nanoparticles (Ni, Pt and FeAl) embedded inside. In the second method, free radical-thermally initiated polymerization was used to polymerize a monomer vapor of styrene on the surfaces of activated Ni nanoparticles.

Abdelsayed, Victor Maher

83

Producing titanium powder by continuous vapor-phase reduction  

NASA Astrophysics Data System (ADS)

One of the goals of the U.S. Department of Energy’s Albany Research Center is to reduce the cost of titanium parts by developing a continuous titanium process. In this work, titanium powder was produced by feeding liquid TiCl4, with argon as a carrier gas, and magnesium wire into a shaft reactor at 1,000°C. The magnesium and TiCl4 vaporized and reacted to produce a mixture of titanium, MgCl2, and magnesium powder. Ti/Mg/MgCl2 powder was removed from the argon gas stream by an electrostatic precipitator, and the titanium powder was separated from the magnesium and MgCl2 by either vacuum distillation or leaching. Vacuum distillation produced sintered titanium powder with lower oxygen levels, but unacceptably high levels of magnesium and chlorine. Leached powder was spherical and free-flowing with low levels of magnesium and chlorine, but the oxygen content was no lower than 0.82%. The high oxygen content of the leached powder is caused by surface oxidation of the submicrometer titanium powder.

Hansen, Dennis A.; Gerdemann, Stephen J.

1998-11-01

84

Large core Yb-doped optical fiber through vapor phase doping technique  

NASA Astrophysics Data System (ADS)

Rare earth (RE) doped optical fibers have shown tremendous progress for producing high power fiber lasers for industrial, medical and strategic applications. However, fabrication of large core, high Yb-doped fiber is still a challenge through conventional process due to poor repeatability and limitation regarding core size. This paper presents successful fabrication of Yb-doped fibers through vapor phase doping technique. Preform fabrication was carried out using a specially constructed MCVD system containing High Temperature Vapor Delivery Unit with sublimators for Al and Yb precursors. The novelty of the present work lies in deposition of Al2O3 and Yb2O3 in vapor phase simultaneously with silica during formation of sintered core layer which result in uniform dopants distribution in the preform. The fibers exhibited lasing efficiency of 76% with low `photodarkening effect'.

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

2013-05-01

85

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

86

Heterodyne phase shift diagnostic for measuring atomic vapor density  

SciTech Connect

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

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

1987-11-12

87

Gallium hydride vapor phase epitaxy of GaN nanowires  

PubMed Central

Straight GaN nanowires (NWs) with diameters of 50 nm, lengths up to 10 ?m and a hexagonal wurtzite crystal structure have been grown at 900°C on 0.5 nm Au/Si(001) via the reaction of Ga with NH3 and N2:H2, where the H2 content was varied between 10 and 100%. The growth of high-quality GaN NWs depends critically on the thickness of Au and Ga vapor pressure while no deposition occurs on plain Si(001). Increasing the H2 content leads to an increase in the growth rate, a reduction in the areal density of the GaN NWs and a suppression of the underlying amorphous (?)-like GaN layer which occurs without H2. The increase in growth rate with H2 content is a direct consequence of the reaction of Ga with H2 which leads to the formation of Ga hydride that reacts efficiently with NH3 at the top of the GaN NWs. Moreover, the reduction in the areal density of the GaN NWs and suppression of the ?-like GaN layer is attributed to the reaction of H2 with Ga in the immediate vicinity of the Au NPs. Finally, the incorporation of H2 leads to a significant improvement in the near band edge photoluminescence through a suppression of the non-radiative recombination via surface states which become passivated not only via H2, but also via a reduction of O2-related defects. PMID:21711801

2011-01-01

88

ORGANIC CHARACTERIZATION OF AEROSOLS AND VAPOR PHASE COMPOUNDS IN URBAN ATMOSPHERES  

EPA Science Inventory

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

89

Mechanism of ellipsometry monolayer oscillations during metalorganic vapor-phase epitaxy  

Microsoft Academic Search

Ellipsometry signal oscillations were clearly seen during metalorganic vapor-phase epitaxy (MOVPE) of III-V materials under high sample rotation at 1400 rpm. The ellipsometric signal oscillated at a period corresponding to 1 ML of MOVPE growth. Oscillations correlated with the formation of islands due to nucleation on terraces during the growth of 1 ML. Different surface reconstructions between (100) terraces (As

Jeong-Sik Lee; Shigeo Sugou; Yasuaki Masumoto

2000-01-01

90

KINETIC MODELING OF DOPANT AND IMPURITY SURFACE SEGREGATION DURING VAPOR PHASE GROWTH: MULTIPLE MECHANISM APPROACH  

E-print Network

KINETIC MODELING OF DOPANT AND IMPURITY SURFACE SEGREGATION DURING VAPOR PHASE GROWTH: MULTIPLE for the experimentally measured segregation length and profile broadening that can be readily calculated without the need in attempts to attain sharp doping profiles in silicon [5]. There had been extensive work on understanding

Arnold, Craig B.

91

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. ...

92

Vapor phase polymerization of poly (3,4-ethylenedioxythiophene) on flexible substrates for enhanced transparent electrodes  

Microsoft Academic Search

Recently, conducting polymer thin films have been investigated as transparent electrodes in photovoltaic devices and organic light emitting diodes. Due to its relatively high conductivity and excellent transmission in the visible region, poly (3, 4-ethyelenedioxythiophene) (PEDOT) has been shown to be a viable option for such applications. Herein described is a method for the vapor phase polymerization (VPP) of transparent

Christopher M. Madl; Peter N. Kariuki; Jessica Gendron; Louis F. J. Piper; Wayne E. Jones

2011-01-01

93

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

94

Sulfur Impregnation on Activated Carbon Fibers through H2S Oxidation for Vapor Phase  

E-print Network

Sulfur Impregnation on Activated Carbon Fibers through H2S Oxidation for Vapor Phase Mercury: Sulfur was impregnated onto activated carbon fibers ACFs through H2S oxidation catalyzed by the sorbent surface in a fixed-bed reactor. By changing the temperature and duration of the sulfur impregnation

Borguet, Eric

95

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

96

SIMULTANEOUS ABSORPTION OF VAPOR PHASE POLYCYCLIC AROMATIC HYDROCARBON AND CARBON DIOXIDE IN ANIONIC SURFACTANT SOLUTIONS  

Microsoft Academic Search

The goal of this work was to investigate whether the solubility of vapor phase polycyclic aromatic compounds (PAHs) and CO2 in water could be enhanced by adding anionic surfactant during the absorption process. Naphthalene was the PAH surrogate and sodium dodecyl sulfate (SDS) was the anionic surfactant. A series of batch experiments in an absorption cell were performed at 50°C

Hsiao-Lin Huang; Whei-May Grace Lee

2001-01-01

97

The chemistry of the organometallic vapor-phase epitaxy of mercury cadmium telluride  

Microsoft Academic Search

This review of the organometallic vapor-phase epitaxy (OMVPE) of mercury cadmium telluride examines the chemistry underlying film growth, film morphology, heteroepitaxy, doping, and reactor design. A key feature of the OMVPE of II-VI compounds, as distinguished from the OMVPE of III-V compounds, is that the intrinsic reaction kinetics control film growth. The rates of surface and gas-phase reactions determine the

ROBERT F. HICKS

1992-01-01

98

Relaxed InxGa1 xAs graded buffers grown with organometallic vapor phase epitaxy on GaAs  

E-print Network

Relaxed InxGa1 xAs graded buffers grown with organometallic vapor phase epitaxy on GaAs Mayank T with compositionally graded buffers were grown with organometallic vapor phase epitaxy on GaAs substrates nearly complete relaxed graded buffers with the most uniform composition caps. With the optimum growth

99

Higher cigarette prices influence cigarette purchase patterns  

Microsoft Academic Search

Objective: To examine cigarette purchasing patterns of current smokers and to determine the effects of cigarette price on use of cheaper sources, discount\\/generic cigarettes, and coupons.Background: Higher cigarette prices result in decreased cigarette consumption, but price sensitive smokers may seek lower priced or tax-free cigarette sources, especially if they are readily available. This price avoidance behaviour costs states excise tax

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

2005-01-01

100

New low toxicity, multi-metal active vapor phase corrosion inhibitors  

SciTech Connect

Traditional vapor phase corrosion inhibitors (VCIs) were developed for short-term protection of steel articles. VCIs have been applied for protecting metallic structures between stages of manufacturing, between manufacturing and deployment, and in enclosed service environments. Some of the problems associated with this corrosion inhibiting application include: protecting dissimilar metallic structures, avoiding toxic materials such as nitrite salts and formaldehyde emitting compounds, an the need for longer duration corrosion protection. Several types of organic compounds were derivatized for temporary volatility and formulated to yield materials with sufficient ambient temperature vapor pressure for VCI application. The ability of these new VCIs to prevent vapor phase metallic corrosion was investigated by an accelerated hydrothermal exposure method. Metals investigated included an aluminum aircraft alloy, cold rolled steel, brass and a copper-nickel alloy. Potentiodynamic slow scan electrochemical analysis and SEM were also used to study the surface behavior and corrosion processes for metallic specimens treated with experimental and control VCIS. Several of the new compounds showed significant vapor phase corrosion inhibition on all four metal alloys.

Cole, D.E.; Dixon, B.G.; Koehan, F.L.

1999-07-01

101

Menstrual cycle phase effects on nicotine withdrawal and cigarette craving: a review.  

PubMed

Evidence suggests that women are less likely to quit smoking than are men. This may reflect differences in nicotine dependence and, more specifically perhaps, nicotine withdrawal and craving. However, there is conflicting research on gender differences on the experience of withdrawal and craving. Menstrual cycle effects may moderate this relationship. Given hormonal changes during the menstrual cycle, abstinence-related symptoms such as withdrawal and craving may vary as a function of menstrual phase as well. This qualitative review summarizes the modest but expanding body of research in this area. One of the challenges inherent in interpreting this literature is the difficulty in distinguishing withdrawal symptomatology from premenstrual symptomatology. Methodological variation, including limited sample size and possible selection bias, in which several studies finding null effects excluded women with severe premenstrual dysphoric disorder, may explain some of the inconsistent findings across studies. Nonetheless, some of the 13 studies included in this review found heightened experiences of withdrawal or craving within the latter days of the menstrual cycle (i.e., the luteal phase). Further research is necessary to replicate these findings, but they may suggest the need for focused cessation treatment during the luteal phase or quit attempts that are well timed relative to specific menstrual phases. PMID:17008190

Carpenter, Matthew J; Upadhyaya, Himanshu P; LaRowe, Steven D; Saladin, Michael E; Brady, Kathleen T

2006-10-01

102

Resonant Acoustic Measurement of Vapor Phase Transport Phenomenon  

NASA Astrophysics Data System (ADS)

A major impediment to accurate non steady-state diffusion measurements is the ability to accurately measure and track a rapidly changing gas concentration without disturbing the system. Non-destructive methods that do not interfere with system dynamics have been developed in the past. These methods, however, have tended to be cumbersome or inaccurate at low concentrations. A new experimental approach has been developed to measure gaseous diffusion in free air and through porous materials. The method combines the traditional non steady-state laboratory methodology with resonant acoustic gas analysis. A phase-locked-loop (PLL) resonance frequency tracker is combined with a thermally insulated copper resonator. A piston sealed with a metal bellows excites the fundamental standing wave resonance of the resonator. The PLL maintains a constant phase difference (typically 90§) between the accelerometer mounted on the piston and a microphone near the piston to track the resonance frequency in real time. A capillary or glass bead filled core is fitted into an o-ring sealed opening at the end of the resonator opposite the bellows. The rate at which the tracer gas is replaced by air within the resonator is controlled by the diffusion coefficient of the gas in free air through the capillary (DA) or by the effective diffusion coefficient of the gas through the core (De). The mean molecular weight of the gas mixture in the resonator is directly determined six times each minute from the ratio of the absolute temperature to the square of the fundamental acoustic resonance frequency. Average system stability (temperature divided by frequency squared) is better than 350 ppm. DA values for a 0.3-inch diameter capillary were in excellent agreement with published values. De values for porous media samples (0.5 mm glass beads) of four different lengths (1 through 4 inches) using three different tracer gases (He, CH4, Kr) will be reported. Comments will be offered regarding tracer gas selection and device orientation and their effect on experimental results. [Work supported by the Office of Naval Research.

Schuhmann, R. J.; Garrett, S. L.; Matson, J. V.

2002-12-01

103

Novel Process for Removal and Recovery of Vapor Phase Mercury  

SciTech Connect

We demonstrated in the Phase I program all key attributes of a new technology for removing mercury from flue gases, namely, a) removal of greater than 95% of both elemental and oxidized forms of mercury, both in the laboratory and in the field b) regenerability of the sorbent c) ability to scale up, and d) favorable economics. The Phase I program consisted of four tasks other than project reporting: Task I-1 ? Screen Sorbent Configurations in the Laboratory Task I-2 ? Design and Fabricate Bench-Scale Equipment Task I-3 ? Test Bench-Scale Equipment on Pilot Combustor Task I-4 ? Evaluate Economics Based on Bench-Scale Results In Task I-1, we demonstrated that the sorbents are thermally durable and are regenerable through at least 55 cycles of mercury uptake and desorption. We also demonstrated two low-pressure- drop configurations of the sorbent, namely, a particulate form and a monolithic form. We showed that the particulate form of the sorbent would take up 100% of the mercury so long as the residence time in a bed of the sorbent exceeded 0.1 seconds. In principle, the particulate form of the sorbent could be imbedded in the back side of a higher temperature bag filter in a full-scale application. With typical bag face velocities of four feet per minute, the thickness of the particulate layer would need to be about 2000 microns to accomplish the uptake of the mercury. For heat transfer efficiency, however, we believed the monolithic form of the sorbent would be the more practical in a full scale application. Therefore, we purchased commercially-available metallic monoliths and applied the sorbent to the inside of the flow channels of the monoliths. At face velocities we tested (up to 1.5 ft/sec), these monoliths had less than 0.05 inches of water pressure drop. We tested the monolithic form of the sorbent through 21 cycles of mercury sorption and desorption in the laboratory and included a test of simultaneous uptake of both mercury and mercuric chloride. Overall, in Task I-1, we found that the particulate and monolith forms of the sorbent were thermally stable and durable and would repeatedly sorb and desorb 100% of the mercury, including mercuric chloride, with low pressure drop and short residence times at realistic flue gas conditions.

Collin Greenwell; Daryl L. Roberts; Jason Albiston; Robin Stewart; Tom Broderick

1998-03-09

104

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

PubMed

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. PMID:23485287

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

2013-03-01

105

Mid-infrared laser-absorption diagnostic for vapor-phase fuel mole fraction and liquid fuel film thickness  

Microsoft Academic Search

A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C-H stretching band of vapor

J. M. Porter; J. B. Jeffries; R. K. Hanson

2010-01-01

106

Mid-infrared laser-absorption diagnostic for vapor-phase fuel mole fraction and liquid fuel film thickness  

Microsoft Academic Search

A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C-H stretching band of vapor

J. M. Porter; J. B. Jeffries; R. K. Hanson

2011-01-01

107

Rules governing vapor-phase extraction of carboxylic acids and phenols from aqueous solutions  

NASA Astrophysics Data System (ADS)

The influence of the molecular structure of the components to be extracted and the type of the extractant used on the effectiveness of vapor-phase extraction from water was studied for the example of low-molecular-weight carboxylic acids C2-C6 and phenols. Extraction parameters were found to depend on the length of the analyte molecule and its polarity. The experimental data and correlations observed substantiated the validity of the suggested mechanism of vapor-phase extraction. Changes in the Gibbs energy of extraction equilibrium as the length of the analyte molecule (in the homologous series of organic acids C2-C6) and molecule polarity (for the example of cresol isomers) increased were evaluated.

Bekhterev, V. N.

2008-06-01

108

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

109

Erbium-Doped ZnO Prepared by Vapor-Phase Transport  

NASA Astrophysics Data System (ADS)

Erbium-doped ZnO has been prepared by vapor-phase transport. ZnO powder, graphite powder, and Er2O3 powder were mixed at a molar ratio of 1:1:0.2 and heated at 1054 °C. Erbium-doped ZnO was deposited on n-type (100)Si wafers located in the same temperature zone. The photoluminescence of the as-deposited sample shows a strong ZnO band-gap emission near 378 nm. After annealing, green emissions at 548, 566, 576, 585, and 595 nm were observed, which correspond to the 4 f inner shell transition of erbium from 2H11/2 to 4I15/2 and 4S3/2 to 4I15/2. Our results indicate that vapor-phase transport is an alternative route for doping ZnO with erbium.

Chao, Liang-Chiun; Chiang, Ping-Chang; Yang, Shih-Hsuan; Huang, Jian-Wei; Liau, Chung-Chi; Chen, Jyh-Shin; Su, Chien-Ying

2006-09-01

110

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

111

Progress toward cascade cells made by OM-VPE. [organometallic vapor phase epitaxy  

NASA Technical Reports Server (NTRS)

Organometallic Vapor Phase Epitaxy (COM-VPE) was used to make a sophisticated monolithic cascade cell, with a peak AMO efficiency of 16.6%, not corrected for 14% grid coverage. The cell has 9 epitaxial layers. The top cell is 1.35 microns thick with a 0.1 micron thich emitter. Both cells are heteroface n-p structures. The cascade cell uses metal interconnects. Details of growth and processing are described.

Borden, P. G.; Larue, R. A.; Ludowise, M. J.

1982-01-01

112

Real-time monitoring of ellipsometry monolayer oscillations during metalorganic vapor-phase epitaxy  

Microsoft Academic Search

Ellipsometry signal oscillations were clearly seen during metalorganic vapor-phase epitaxy (MOVPE) of III–V materials under high sample rotation at 1400rpm. The ellipsometric signal was found to oscillate at a period corresponding to 1 monolayer of MOVPE growth. Oscillations correlated with the formation of islands due to nucleation on terraces during the growth of 1 monolayer. Layer thickness and composition of

Jeong-Sik Lee; Yasuaki Masumoto

2000-01-01

113

Characterization of Cu2ZnSnS4 Thin Films Prepared by Vapor Phase Sulfurization  

Microsoft Academic Search

Cu2ZnSnS4 (CZTS) thin films could be successfully formed by vapor phase sulfurization of electron-beam-evaporated precursors on a soda-lime glass substrate. This film is an interesting material for absorber layer in a solar cell because all the constituents are readily available in the earth's crust. In this study, using a new type of precursors containing ZnS, we could achieve the strong

Hironori Katagiri; Naoya Ishigaki; Takeshi Ishida; Kotoe Saito

2001-01-01

114

Vapor-phase elemental mercury adsorption by activated carbon impregnated with chloride and chelating agents  

Microsoft Academic Search

The dynamic adsorption capacity for vapor-phase elemental mercury (Hg0) of commercially available granular activated carbon (BPL) impregnated with copper chloride (BPL-C), ?-aminoanthraquinone (BPL-A), 2-(aminomethyl)pyridine (BPL-P), and 2-aminoethanethiol (BPL-T) was studied in an attempt to produce economical and effective sorbents for the control of elemental mercury emissions from combustion processes. The dynamic adsorption capacity of BPL-C was found to increase as

Radisav D Vidic; Douglas P Siler

2001-01-01

115

Free-Standing GaN Substrates by Hydride Vapor Phase Epitaxy  

Microsoft Academic Search

Thick gallium nitride films 250-350 mum in thickness were grown on 2-inch-diameter (0001) sapphire wafers by hydride vapor phase epitaxy. The size of the free-standing GaN substrates without cracks separated from the sapphire substrates by laser processing was equal to that of the initial sapphire substrates. The origin of bowing and the broad photoluminescence (PL) spectra of GaN films was

Sung S. Park; Il-W. Park; Sung H. Choh

2000-01-01

116

Inner pressure control method in optical fiber preform fabrication by vapor-phase axial deposition  

Microsoft Academic Search

A method to control inner pressure variation in a vapor-phase axial-deposition (VAD) apparatus is developed. It uses a flame-detection technology to explain temperature fluctuations. Primary causes of the inner pressure fluctuations are analyzed, and suppression techniques are described. They include the adoption of a large buffer-tank and bias gas addition. An inner pressure-feedback control mechanism operates by adjusting the bias

Katsuyuki Imoto; Masao Sumi

1988-01-01

117

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

Microsoft Academic Search

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

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

2011-01-01

118

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

Microsoft Academic Search

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

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

1994-01-01

119

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

120

Vapor phase analysis of aromatic organic compounds using laser-induced fluorescence and fiber optics  

NASA Astrophysics Data System (ADS)

Prior work has reported on the usefulness of fiber optic sensors in the detection of dissolved aromatic organic ground water contaminants such as the benzene, toluene, ethylbenzene, and xylenes (BTEX) fraction of petroleum fuels. Our device is a laser fluorimeter using fiber optic sensors for in situ measurements. Fluorescence intensity and lifetime can be measured at any wavelength in order to compare concentrations and discriminate certain compounds. Our instrument configuration uses a pulsed Nd:YAG laser twice frequency doubled to provide 266 nm excitation light. Excitation light, and subsequent induced fluorescence, are carried to the location of interest by a pair of 600 micron core fused silica optical fibers. Fluorescence is measured using a photomultiplier (PMT). PMT output goes either into a high-speed oscilloscope for fluorescence lifetime measurements or into a gated integrator for fluorescence intensity measurements. The same system can be used to detect aromatic contaminants in the vapor phase. Phenol, toluene, and xylene have been tested in the vapor phase. Concentrations below 10 micrograms phenol per liter air are detectable. In the vapor phase, the water Raman line seen around 295 nm in aqueous solution is insignificant, allowing a greater wavelength range to be scanned by the detector. Fluorescence spectra, fluorescence lifetimes, and fluorescence versus concentration information are presented. Applications of this approach to vadose zone ground water monitoring are discussed.

Chudyk, Wayne; Botteron, Carol; Pohlig, Kenneth

1992-03-01

121

Metastable phase formation in thin films formed by laser breakdown chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Thin films produced by laser breakdown chemical vapor deposition (LBCVD) from Ni and Fe carbonyls were examined and their structure characterized, with emphasis on identifying the phases present. A brightfield micrograph observed in the Ni samples and the corresponding selected area diffraction (SAD) pattern are shown along with two darkfield micrographs of Ni-C film obtained from two positions on the same diffraction ring. It is seen that the decomposition of both carbonyls results in the formation of a supersaturated fcc phase and the carbide phase. The study shows that even a severe quench from the gas phase fails to completely stop the system from approaching its equilibrium structure. This indicates that the carbides Ni3C and Fe3C are associated with a very high thermodynamic driving force for their formation even though both of these phases are metastable.

Menon, S. K.; Jervis, T. R.

1986-11-01

122

Effects of vapor-phase deposition processes on the optical, chemical, and magnetic properties OE the lunar regolith  

Microsoft Academic Search

The processes of solar wind sputtering and meteoritic impact vaporization have created materials in the lunar regolith which were deposited from a vapor phase. Although the quantity of such exotic condensed substances should theoretically be comparable with that of materials which have been melted by impacts, their existence in the fines has not been generally recognized. We have investigated the

Bruce Hapke; William Cassidy; Edward Wells

1975-01-01

123

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

E-print Network

deposition 1. Introduction The lubrication of ceramic surfaces working at extremely high temperatures has 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

Gellman, Andrew J.

124

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

125

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

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

126

Ordered organic thin films self-assembled from the vapor phase  

NASA Technical Reports Server (NTRS)

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

Debe, M. K.

1993-01-01

127

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

128

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

129

Higher cigarette prices influence cigarette purchase patterns  

PubMed Central

Objective: To examine cigarette purchasing patterns of current smokers and to determine the effects of cigarette price on use of cheaper sources, discount/generic cigarettes, and coupons. Background: Higher cigarette prices result in decreased cigarette consumption, but price sensitive smokers may seek lower priced or tax-free cigarette sources, especially if they are readily available. This price avoidance behaviour costs states excise tax money and dampens the health impact of higher cigarette prices. Methods: Telephone survey data from 3602 US smokers who were originally in the COMMIT (community intervention trial for smoking cessation) study were analysed to assess cigarette purchase patterns, use of discount/generic cigarettes, and use of coupons. Results: 59% reported engaging in a high price avoidance strategy, including 34% who regularly purchase from a low or untaxed venue, 28% who smoke a discount/generic cigarette brand, and 18% who report using cigarette coupons more frequently that they did five years ago. The report of engaging in a price avoidance strategy was associated with living within 40 miles of a state or Indian reservation with lower cigarette excise taxes, higher average cigarette consumption, white, non-Hispanic race/ethnicity, and female sex. Conclusion: Data from this study indicate that most smokers are price sensitive and seek out measures to purchase less expensive cigarettes, which may decrease future cessation efforts. PMID:15791017

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

2005-01-01

130

Ex situ vapor phase boron doping of silicon nanowires using BBr3.  

PubMed

An ex situ vapor phase technique for doping vapor-liquid-solid grown silicon nanowires (NWs) based on the reduction of BBr(3) by H(2) has been demonstrated. Electron microscope images show that the excellent crystal quality of the nanowires is preserved with minimal alteration of their surface morphology. Fano resonance in the Raman spectra for single nanowires indicates that active boron concentrations over two orders of magnitude and as high as 10(20) cm(-3) are achievable in a well-controlled manner, with excellent axial uniformity. Electrical resistance measurements from single nanowires confirm that incorporated boron is electrically active, and doping of epitaxial bridging Si NWs is successfully demonstrated. By avoiding the pitfalls of nonuniform concentration profiles and drastic morphological changes that often accompany in situ boron doping, this technique provides a valuable alternative doping route for the development of single Si NW devices in a reliable manner. PMID:20648344

Doerk, Gregory S; Lestari, Gabriella; Liu, Fang; Carraro, Carlo; Maboudian, Roya

2010-07-01

131

Phase Composition and Microstructural Responses of Graded Mullite/YSZ Coatings Under Water Vapor Environments  

NASA Astrophysics Data System (ADS)

Mullite-based systems have been considered as environmental barrier coatings (EBCs) for high temperature protection of Si-based ceramic (Si3N4, SiC) substrates against water vapor corrosion, for application in forthcoming turbine engines. Graded mullite/Y-ZrO2 composites plasma sprayed over Hexoloy SiC substrates were analyzed as EBCs. All feedstock materials were purposely prepared and singular spraying conditions were used to assure superior crystallization. The different coated specimens were subjected to temperatures of 1300 °C for 100-500 h under water vapor environment. The effect of water corrosion on the exposed coatings was investigated by focusing on their phase and microstructure changes.

Garcia, E.; Mesquita-Guimarães, J.; Miranzo, P.; Osendi, M. I.; Cojocaru, C. V.; Wang, Y.; Moreau, C.; Lima, R. S.

2011-01-01

132

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

133

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

134

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

135

E-Cigarettes  

MedlinePLUS

... Media: Connect With Us E-Cigarettes KidsHealth > Parents > School & Family Life > ... About E-Cigarettes E-cigarettes are being marketed as a safe alternative to smoking. But they're not because e- ...

136

Role of vapor-phase mass transport during the spreading of a long-chain alkane drop.  

PubMed

The spreading of liquid alkanes over solid surfaces has important applications in painting, coatings, lubrication, and petroleum tertiary recovery. The role of the vapor-phase mass transport accompanying liquid spreading has not been well studied because it is difficult to separate the contributions from the liquid spreading and the vapor-phase transport that occurred at the same time. We used the engineered surface patterns to study the vapor-phase mass transport during liquid spreading. First, we fabricated several hydrophilic, carboxylic acid-terminated patterns (OTSpd) on a hydrophobic, methyl-terminated octadecyltrichlorosilane (OTS) surface. These OTSpd patterns did not connect to each other. Next, we let an alkane drop spread within one OTSpd pattern. The liquid alkane could not spread to other OTSpd patterns because OTS separated them; however, the alkane molecules in the vapor phase could migrate and adsorb on other OTSpd patterns. Therefore, the contributions from the liquid spreading and the vapor-phase transport were separated and could be investigated independently. We found that during the spreading of the liquid alkane, mass transport through the vapor phase cannot be ignored. Alkane molecules adsorbed on the OTSpd surface with their backbones parallel to the surface in the first few layers. Additional alkane molecules adsorbed on these parallel layers to form the seaweed-shaped layers in which the alkane molecules stood up. Our study showed that the parallel layers formed from the vapor-phase mass transport before the liquid alkane spread. Therefore, the liquid alkane does not spread over the more strongly binding OTSpd surface. It actually spreads over the parallel alkane layer, which formed from its own vapor. PMID:19580290

Lu, Lingbo; Cai, Yuguang

2009-12-15

137

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

138

Comparative study of solution-phase and vapor-phase deposition of aminosilanes on silicon dioxide surfaces.  

PubMed

The uniformity of aminosilane layers typically used for the modification of hydroxyl bearing surfaces such as silicon dioxide is critical for a wide variety of applications, including biosensors. However, in spite of many studies that have been undertaken on surface silanization, there remains a paucity of easy-to-implement deposition methods reproducibly yielding smooth aminosilane monolayers. In this study, solution- and vapor-phase deposition methods for three aminoalkoxysilanes differing in the number of reactive groups (3-aminopropyl triethoxysilane (APTES), 3-aminopropyl methyl diethoxysilane (APMDES) and 3-aminopropyl dimethyl ethoxysilane (APDMES)) were assessed with the aim of identifying methods that yield highly uniform and reproducible silane layers that are resistant to minor procedural variations. Silane film quality was characterized based on measured thickness, hydrophilicity and surface roughness. Additionally, hydrolytic stability of the films was assessed via these thickness and contact angle values following desorption in water. We found that two simple solution-phase methods, an aqueous deposition of APTES and a toluene based deposition of APDMES, yielded high quality silane layers that exhibit comparable characteristics to those deposited via vapor-phase methods. PMID:24411379

Yadav, Amrita R; Sriram, Rashmi; Carter, Jared A; Miller, Benjamin L

2014-02-01

139

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

140

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

141

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

142

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

143

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

NASA Astrophysics Data System (ADS)

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

Sharma, S.; Spencer, S.

2008-12-01

144

Vapor-phase chemical synthesis of magnesium oxide nanowires by DC arc discharge  

Microsoft Academic Search

Magnesium oxide (MgO) nanowires have been synthesized by DC arc discharge without using metal catalysts. These MgO nanowires\\u000a are single-crystalline, with an axes along the [100] direction. The cross sectional diameter of the nanowires spans the range\\u000a of 5–150 nm, with the length up to hundreds of micrometers. The growth of MgO nanowires can be considered as a vapor-phase\\u000a chemical reaction

Yanjie Su; Hao Wei; Zhi Yang; Liangming Wei; Eric Siu-Wai Kong; Yafei Zhang

145

Vapor phase growth technique of III-V compounds utilizing a preheating step  

NASA Technical Reports Server (NTRS)

In the vapor phase epitaxy fabrication of semiconductor devices and in particular semiconductor lasers, the deposition body on which a particular layer of the laser is to be grown is preheated to a temperature about 40.degree. to 60.degree. C. lower than the temperature at which deposition occurs. It has been discovered that by preheating at this lower temperature there is reduced thermal decomposition at the deposition surface, especially for semiconductor materials such as indium gallium phosphide and gallium arsenide phosphide. A reduction in thermal decomposition reduces imperfections in the deposition body in the vicinity of the deposition surface, thereby providing a device with higher efficiency and longer lifetime.

Olsen, Gregory Hammond (Inventor); Zamerowski, Thomas Joseph (Inventor); Buiocchi, Charles Joseph (Inventor)

1978-01-01

146

Erbium-Doped ZnO Prepared by Vapor-Phase Transport  

Microsoft Academic Search

Erbium-doped ZnO has been prepared by vapor-phase transport. ZnO powder, graphite powder, and Er2O3 powder were mixed at a molar ratio of 1:1:0.2 and heated at 1054 °C. Erbium-doped ZnO was deposited on n-type (100)Si wafers located in the same temperature zone. The photoluminescence of the as-deposited sample shows a strong ZnO band-gap emission near 378 nm. After annealing, green

Liang-Chiun Chao; Ping-Chang Chiang; Shih-Hsuan Yang; Jian-Wei Huang; Chung-Chi Liau; Jyh-Shin Chen; Chien-Ying Su

2006-01-01

147

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

148

Electro-optic polyurea waveguides by in-situ polymerization from the vapor phase  

NASA Astrophysics Data System (ADS)

Electro-optically active planar waveguides of aromatic polyurea were prepared by simultaneous deposition of 4,4'-diamino-diphenyl-methane and 4,4'-diphenylmethane- diisocyanate from the vapor phase and subsequent corona poling. Attenuated total reflectance spectroscopy of the waveguide modes of the polymer films was used to measure the piezoelectric and electro-optic susceptibilities. It is found that the electro-optic response is not only determined by the nonlinear polarizability of the urea groups but also from their dipolar orientation in the applied field.

Herminghaus, Stephan; Aust, Emil; Knoll, Wolfgang; Takahashi, Yoshikazu; Fukada, Eiichi

1993-12-01

149

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

150

Growth of AlBN solid solutions by organometallic vapor-phase epitaxy  

NASA Astrophysics Data System (ADS)

Layers of AlBN were grown on sapphire by organometallic vapor-phase epitaxy at 1050 °C using triethylboron, trimethylaluminum, and ammonia as precursors. It is shown that boron is readily incorporated into the layers and its concentration in the solid phase can be as high as 40%. However, single phase Al1-xBoverflow="scroll">xN films can only be grown for compositions not exceeding x=0.01. For higher boron concentrations in the solid the second B-rich phase is formed. This phase was identified as wurtzite BN based on the results of transmission electron microscopy and x-ray diffraction. The growth of this thermodynamically unfavorable phase becomes possible, most probably, because it occurs within the framework provided by wurtzite AlN islands first formed on the surface and setting up the sites for lateral growth of wurtzite BN. That leads to formation of columnar structure of AlN and BN crystallites oriented in the basal plane and existing side by side.

Polyakov, A. Y.; Shin, M.; Qian, W.; Skowronski, M.; Greve, D. W.; Wilson, R. G.

1997-02-01

151

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

152

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

153

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

154

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

155

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

156

Mid-infrared laser-absorption diagnostic for vapor-phase fuel mole fraction and liquid fuel film thickness  

Microsoft Academic Search

A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase\\u000a fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C–H stretching band of vapor\\u000a n-decane

J. M. Porter; J. B. Jeffries; R. K. Hanson

2011-01-01

157

Vapor-phase synthesis of uniform silica spheres through two-stage hydrolysis of SiCl{sub 4}  

SciTech Connect

We report, for the first time, a vapor-phase synthesis of nearly monodispersed silica spheres 250-300 nm in size through a two-stage hydrolysis of SiCl{sub 4}. In the first stage, SiCl{sub 4} vapor was partially hydrolyzed with water vapor in a batch reactor at 150 deg. C to form silicon oxychloride particles, nearly monodispersed and spherical. In the second stage, these oxychloride particles were converted into silica particles through further hydrolysis at 1000 deg. C in a tubular reactor, while the morphology and size after the first-stage reaction remained virtually unchanged.

Park, Hoey K. [Department of Chemical Engineering, Kongju National University, 182 Shinkwandong, Kongju, Chungnam 314-701 (Korea, Republic of); Park, Kyun Y. [Department of Chemical Engineering, Kongju National University, 182 Shinkwandong, Kongju, Chungnam 314-701 (Korea, Republic of)], E-mail: kypark@kongju.ac.kr

2008-11-03

158

APTS and rGO co-functionalized pyrenated fluorescent nanonets for representative vapor phase nitroaromatic explosive detection  

NASA Astrophysics Data System (ADS)

For the first time, flexible PVP/pyrene/APTS/rGO fluorescent nanonets were designed and synthesized via a one-step electrospinning method to detect representative subsaturated nitroaromatic explosive vapor. The functional fluorescent nanonets, which were highly stable in air, showed an 81% quenching efficiency towards TNT vapor (~10 ppb) with an exposure time of 540 s at room temperature. The nice performance of the nanonets was ascribed to the synergistic effects induced by the specific adsorption properties of APTS, the fast charge transfer properties and the effective ?-? interaction with pyrene and TNT of rGO. Compared to the analogues of TNT, the PVP/pyrene/APTS/rGO nanonets showed notable selectivity towards TNT and DNT vapors. The explored functionalization method opens up brand new insight into sensitive and selective detection of vapor phase nitroaromatic explosives.For the first time, flexible PVP/pyrene/APTS/rGO fluorescent nanonets were designed and synthesized via a one-step electrospinning method to detect representative subsaturated nitroaromatic explosive vapor. The functional fluorescent nanonets, which were highly stable in air, showed an 81% quenching efficiency towards TNT vapor (~10 ppb) with an exposure time of 540 s at room temperature. The nice performance of the nanonets was ascribed to the synergistic effects induced by the specific adsorption properties of APTS, the fast charge transfer properties and the effective ?-? interaction with pyrene and TNT of rGO. Compared to the analogues of TNT, the PVP/pyrene/APTS/rGO nanonets showed notable selectivity towards TNT and DNT vapors. The explored functionalization method opens up brand new insight into sensitive and selective detection of vapor phase nitroaromatic explosives. Electronic supplementary information (ESI) available: Vapor pressure of TNT and its analogues, fluorescence quenching kinetics, fluorescence quenching efficiencies and additional SEM images. See DOI: 10.1039/c3nr04960d

Guo, Linjuan; Zu, Baiyi; Yang, Zheng; Cao, Hongyu; Zheng, Xuefang; Dou, Xincun

2014-01-01

159

Carbon monoxide kinetics following simulated cigarette smoking  

SciTech Connect

Carbon monoxide kinetics were measured in the blood (% carboxyhemoglobin) and alveolar phase (ppM carbon monoxide) after simulated cigarette smoking. Cigarette smoking was siumlated using the same amount of carbon monoxide that 2R1F cigarettes manufactured by the Tobacco Research Institute would contain. Ten boluses of air containing carbon monoxide equivalent to smoking one cigarette were inhaled by six healthy nonsmoker volunteers. Carbon monoxide in the air phase was measured by an Ecolyzer and carboxyhemoglobin was measured by a CO-Oximeter. The mean rise in alveolar carbon monoxide immediately and 20 min after inhaling the last bolus was 3.3 and 3.1 ppM, respectively (p<.005). The mean rise in carboxyhemoglobin immediately and 20 min after inhalation of the last bolus was 0.8 and 0.5% respectively (P<.005). The changes in carboxyhemoglobin were found to be similar to changes that occur when one cigarette is actually smoked.

Karnik, A.S. (Wayne State Univ., Detroit, MI); Coin, E.J.

1980-05-01

160

Desalination of water by vapor-phase transport through hydrophobic nanopores  

NASA Astrophysics Data System (ADS)

We propose a new approach to desalination of water whereby a pressure difference across a vapor-trapping nanopore induces selective transport of water by isothermal evaporation and condensation across the pore. Transport of water through a nanopore with saline water on one side and pure water on the other side under a pressure difference was theoretically analyzed under the rarefied gas assumption using a probabilistic framework that accounts for diffuse scattering from the pore walls as well as reflection from the menisci. The analysis revealed that in addition to salinity, temperature, and pressure difference, the nanopore aspect ratio and the probability of condensation of a water molecule incident on a meniscus from the vapor phase, known as the condensation coefficient, are key determinants of flux. The effect of condensation coefficient on mass flux becomes critical when the aspect ratio is small. However, the mass flux becomes independent of the condensation coefficient as the pore aspect ratio increases, converging to the Knudsen flux for long nanopores. For design of a nanopore membrane that can trap vapor, a minimum aspect ratio is derived for which coalescence of the two interfaces on either side of the nanopore remains energetically unfavorable. Based on this design criterion, the analysis suggests that mass flux in the range of 20-70 g/m2 s may be feasible if the system is operated at temperatures in the range of 30-50 °C. The proposed approach further decouples transport properties from material properties of the membrane, which opens the possibility of engineering membranes with appropriate materials that may lead to reverse osmosis membranes with improved flux, better selectivity, and high chlorine resistance.

Lee, Jongho; Karnik, Rohit

2010-08-01

161

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

162

On the deposition of volatiles and semivolatiles from cigarette smoke aerosols: relative rates of transfer of nicotine and ammonia from particles to the gas phase.  

PubMed

The hypothesis that elevated levels of ammonia-releasing compounds in tobacco and ammonia in mainstream (MS) smoke increase the rate and amount of nicotine evaporation from the particles of MS smoke aerosol was examined by kinetic modeling and experiments with MS cigarette smoke. Computational simulation of a kinetic mechanism describing volatile loss of nicotine, ammonia, and acetic acid from an aqueous solution was used to compute the time-dependent concentration of all species in the model. Because of the high volatility of ammonia relative to that of nicotine, variation over a wide range of initial ammonia concentration had no significant effect upon the rate of loss of nicotine from the model system. The effects of a variation in the volatile loss rate constant for ammonia and for the acid were examined. The simulations show that ammonia is lost from the model solution at a greater rate than nicotine and acid, and the loss of volatile acid has a significant role in the rate and amount of nicotine loss. Simulations with a model system undergoing a continuous steady addition of ammonia showed that high rates of ammonia addition could significantly increase the rate of nicotine volatile loss from the model solution. A series of smoking experiments was performed using blended cigarettes connected to a denuder tube. Deposition of smoke constituents can occur directly from the gas phase and by the deposition of smoke aerosol particles themselves. As nicotine exists >99% in the particle phase of MS smoke, in the absence of particle deposition, denuder tube deposition of nicotine occurs via the evaporation-deposition pathway. Solanesol, a nonvolatile tobacco and smoke terpene, was used to quantify the amount of particle deposition onto the denuder tube. The amount of ammonia deposited on the denuder tube was an order of magnitude greater than that of nicotine, showing that ammonia evaporates from the MS smoke particles much faster than does nicotine. The experimental results were supported and explained by the aqueous model simulations. Included in these experiments are cigarettes that differ in their MS smoke ammonia content by a factor of ca. five. However, an increased amount of MS smoke ammonia does not increase the rate of nicotine loss from the particles. The combined results support the conclusion that ammonia in mainstream smoke has little effect, if any, upon the rate and amount of nicotine evaporation from MS smoke particles. PMID:15310234

Seeman, Jeffrey I; Lipowicz, Peter J; Piadé, Jean-Jacques; Poget, Laurent; Sanders, Edward B; Snyder, James P; Trowbridge, Clarence G

2004-08-01

163

Development of an acoustic wave based biosensor for vapor phase detection of small molecules  

NASA Astrophysics Data System (ADS)

For centuries scientific ingenuity and innovation have been influenced by Mother Nature's perfect design. One of her more elusive designs is that of the sensory olfactory system, an array of highly sensitive receptors responsible for chemical vapor recognition. In the animal kingdom this ability is magnified among canines where ppt (parts per trillion) sensitivity values have been reported. Today, detection dogs are considered an essential part of the US drug and explosives detection schemes. However, growing concerns about their susceptibility to extraneous odors have inspired the development of highly sensitive analytical detection tools or biosensors known as "electronic noses". In general, biosensors are distinguished from chemical sensors in that they use an entity of biological origin (e.g. antibody, cell, enzyme) immobilized onto a surface as the chemically-sensitive film on the device. The colloquial view is that the term "biosensors" refers to devices which detect the presence of entities of biological origin, such as proteins or single-stranded DNA and that this detection must take place in a liquid. Our biosensor utilizes biomolecules, specifically IgG monoclonal antibodies, to achieve molecular recognition of relatively small molecules in the vapor phase.

Stubbs, Desmond

164

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

PubMed

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

Peng, Hao; Ding, Guoliang; Hu, Haitao

2011-01-01

165

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

PubMed Central

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

2011-01-01

166

APTS and rGO co-functionalized pyrenated fluorescent nanonets for representative vapor phase nitroaromatic explosive detection.  

PubMed

For the first time, flexible PVP/pyrene/APTS/rGO fluorescent nanonets were designed and synthesized via a one-step electrospinning method to detect representative subsaturated nitroaromatic explosive vapor. The functional fluorescent nanonets, which were highly stable in air, showed an 81% quenching efficiency towards TNT vapor (?10 ppb) with an exposure time of 540 s at room temperature. The nice performance of the nanonets was ascribed to the synergistic effects induced by the specific adsorption properties of APTS, the fast charge transfer properties and the effective ?-? interaction with pyrene and TNT of rGO. Compared to the analogues of TNT, the PVP/pyrene/APTS/rGO nanonets showed notable selectivity towards TNT and DNT vapors. The explored functionalization method opens up brand new insight into sensitive and selective detection of vapor phase nitroaromatic explosives. PMID:24316887

Guo, Linjuan; Zu, Baiyi; Yang, Zheng; Cao, Hongyu; Zheng, Xuefang; Dou, Xincun

2014-01-01

167

Block copolymer self assembly for design and vapor phase synthesis of one-dimensional nanostructured materials  

NASA Astrophysics Data System (ADS)

Block copolymer thin films provide a robust method for generating regular, uniform patterns with sub-100 nanometer length scales over arbitrarily large areas. A significant advantage of such block copolymer-based patterning is its ease of integration with all other aspects of traditional thin-film processing, including plasma-based etching and metallization. Such process compatibility ensures a host of application opportunities in designing material properties through control of their nanostructure. Here, we describe our use of block copolymer self assembly for design and vapor phase synthesis of quasi one-dimensional nanostructured materials made of metals, semiconductors, and insulators. The precise control of surface texture afforded by block copolymer-based patterning can influence macroscopic materials properties such as optical reflectance and hydrophobicity.

Rahman, A.; Black, C. T.

2014-06-01

168

Vapor phase ketonization of acetic acid on ceria based metal oxides  

SciTech Connect

The activities of CeO2, Mn2O3-CeO2 and ZrO2-CeO2 were measured for acetic acid ketonization under reaction conditions relevant to pyrolysis vapor upgrading. We show that the catalyst ranking changed depending on the reaction conditions. Mn2O3-CeO2 was the most active catalyst at 350 oC, while ZrO2 - CeO2 was the most active catalyst at 450 oC. Under high CO2 and steam concentration in the reactants, Mn2O3-CeO2 was the most active catalyst at 350 and 450 °C. The binding energies of steam and CO2 with the active phase were calculated to provide the insight into the tolerance of Mn2O3-CeO2 to steam and CO2.

Liu, Changjun; Karim, Ayman M.; Lebarbier, Vanessa MC; Mei, Donghai; Wang, Yong

2013-12-01

169

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

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

170

Thermodynamic study of ?-Ga2O3 growth by halide vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

?-Ga2O3 growth by halide vapor phase epitaxy (HVPE) was investigated by thermodynamic analysis. GaCl and O2 were determined to be appropriate precursors for the growth of ?-Ga2O3 by HVPE. When H2 is not included in the carrier gas, growth is expected up to 1600 °C. However, with an increase of H2 in the carrier gas, the driving force of Ga2O3 growth decreases. Stable growth at 1000 °C in an inert carrier gas requires an input VI/III ratio above 1. Experimental results for the homoepitaxial growth of ?-Ga2O3 using GaCl and O2 as precursors and N2 as a carrier gas show that ?-Ga2O3 growth by HVPE can be thermodynamically controlled.

Nomura, Kazushiro; Goto, Ken; Togashi, Rie; Murakami, Hisashi; Kumagai, Yoshinao; Kuramata, Akito; Yamakoshi, Shigenobu; Koukitu, Akinori

2014-11-01

171

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

172

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

SciTech Connect

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

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

2003-06-01

173

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

174

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

PubMed

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

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

2012-11-01

175

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...

176

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

PubMed

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

Chi, Kai Hsien; Chang, Moo Been

2005-10-15

177

Mid-infrared laser-absorption diagnostic for vapor-phase fuel mole fraction and liquid fuel film thickness  

NASA Astrophysics Data System (ADS)

A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C-H stretching band of vapor n-decane and liquid n-dodecane near 3.4 ?m (3000 cm-1). n-Dodecane film thicknesses <20 ?m were accurately measured in the absence of vapor, and simultaneous measurements of n-dodecane liquid film thickness and n-decane vapor mole fraction (300 ppm) were measured with <10% uncertainty for film thicknesses <10 ?m. A potential application of the measurement technique is to provide accurate values of vapor mole fraction in combustion environments where strong absorption by liquid fuel or oil films on windows make conventional direct absorption measurements of the gas problematic.

Porter, J. M.; Jeffries, J. B.; Hanson, R. K.

2011-02-01

178

THE EFFECT OF WATER (VAPOR-PHASE) AND CARBON ON ELEMENTAL MERCURY REMOVAL IN A FLOW REACTOR  

EPA Science Inventory

The paper gives results of studying the effect of vapor-phase moisture on elemental mercury (Hgo) removal by activated carbon (AC) in a flow reactor. tests involved injecting AC into both a dry and a 4% moisture nitrogen (N2) /Hgo gas stream. A bituminous-coal-based AC (Calgon WP...

179

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

E-print Network

Formation of etch pits during carbon doping of gallium arsenide with carbon tetrachloride-doped gallium arsenide films grown by metalorganic vapor-phase epitaxy. Deposition was carried out at 505­545 °C with gallium arsenide. Both reactions desorb gallium chlorides and reduce the growth rate, but only the latter

Li, Lian

180

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

181

E-Cigarettes  

MedlinePLUS

... believe the hype that they're a safe alternative to smoking. Unfortunately, they're not: E-cigarettes ... but that doesn't make them a healthy alternative to regular cigarettes. When you use ("vape") an ...

182

An interrogation of the zinc oxide gallium oxide phase space by plasma enhanced chemical vapor deposition  

NASA Astrophysics Data System (ADS)

Polycrystalline metal oxide thin films were deposited by mixing combinations of diethylzinc and trimethylgallium into an oxygen plasma. Plasma-enhanced chemical vapor deposition was shown to be a flexible tool for materials exploration, as the entire zinc-gallium-oxide phase space was explored by simply altering precursor flow rates. Film identification was performed using measurements of intrinsic optical properties as well as X-ray diffraction. The compounds synthesized included zinc oxide, gallium-doped zinc oxide (ZnO:Ga), the spinel ZnGa2O4, and amorphous gallium oxide. A phase diagram was established for PECVD synthesis as a function of the organometallic precursor composition. It was found that gallium addition had a profound impact on both the deposition rate and resistivity of the films. Small levels the gallium addition produced an order of magnitude improvement in both deposition rate and electrical properties. When the gallium fraction was >50% the deposition rate saturated and the films were insulating. Optical emission spectroscopy was used to probe the plasma chemistry of the system. It was shown to be quite complex, typified by the example that decreasing the diethylzinc fraction in the feedstream dramatically increased the density of atomic zinc in the plasma.

Robbins, J. J.; Fry, C.; Wolden, C. A.

2004-03-01

183

Modeling and mass-transfer evaluation in vapor-phase bioreactors  

SciTech Connect

Vapor-phase bioreactors (VPBRs) have been considered for treating gas streams contaminated by volatile organic compounds (VOCs). A VPBR is a gas absorption column that employs a biofilm as a heterogeneous catalyst growing on an artificial porous medium. To aid in the design, scale-up and operation of a VPBR, a phenomenologically-based mathematical model has been developed to describe the steady-state operation of a VPBR. The present version tracks the electron-donor (VOC) and the electron-acceptor (oxygen) in the gas/liquid/biofilm phases within the bioreactor. The model uses a single species in the biofilm with reaction rates modeled by Monod kinetics for the electron acceptor and Haldane kinetics for the electron donor. Bench-scale VPBRs and the model show evidence of electron-acceptor limitation under certain operating conditions. Due to the effects of the inorganic salts and biomass on the apparent Henry`s law coefficients, these coefficients were experimentally determined using reactor effluent. The coefficients were found to be approximately 50% of the published values for the VOCs. Mass-transfer coefficients for the gas-liquid interface are predicted by Onda correlations. Literature shows these correlations to be within 20% of actual coefficients for abiotic systems. Bench-scale experiments using a non-reactive tracer showed that the Onda correlations can overestimate mass-transfer coefficients by as much as three times.

Wend, C.; Jones, W. [Montana State Univ., Bozeman, MT (United States). Center for Biofilm Engineering

1994-12-31

184

Antibacterial effects of allspice, garlic, and oregano essential oils in tomato films determined by overlay and vapor-phase methods.  

PubMed

Physical properties as well as antimicrobial activities against Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes of allspice, garlic, and oregano essential oils (EOs) in tomato puree film-forming solutions (TPFFS) formulated into edible films at 0.5% to 3% (w/w) concentrations were investigated in this study. Antimicrobial activities were determined by 2 independent methods: overlay of the film on top of the bacteria and vapor-phase diffusion of the antimicrobial from the film to the bacteria. The results indicate that the antimicrobial activities against the 3 pathogens were in the following order: oregano oil > allspice oil > garlic oil. Listeria monocytogenes was less resistant to EO vapors, while E. coli O157:H7 was more resistant to EOs as determined by both overlay and vapor-phase diffusion tests. The presence of plant EO antimicrobials reduced the viscosity of TPFFS at the higher shear rates, but did not affect water vapor permeability of films. EOs increased elongation and darkened the color of films. The results of the present study show that the 3 plant-derived EOs can be used to prepare tomato-based antimicrobial edible films with good physical properties for food applications by both direct contact and indirectly by vapors emanating from the films. PMID:19895486

Du, W-X; Olsen, C W; Avena-Bustillos, R J; McHugh, T H; Levin, C E; Mandrell, R; Friedman, Mendel

2009-09-01

185

INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Metal-organic vapor phase epitaxy of (GaAl)As for 0.85-?m laser diodes  

NASA Astrophysics Data System (ADS)

Metal-organic vapor phase epitaxy was used to grow stripe heterolaser diodes that were hitherto fabricated by liquid phase epitaxy. The main relationships between the growth parameters (partial input pressures, temperatures) and the properties of materials (thicknesses, solid-solution compositions, carrier densities) were investigated. The results were in full agreement with the mechanism of growth controlled by a vapor-phase diffusion. The results achieved routinely in the growth of GaAs are reported. It is shown that double heterostructure laser diodes fabricated by metal-organic vapor phase epitaxy compete favorably with those grown so far by liquid phase epitaxy, including their degradation and reliability.

Jacobs, K.; Bugge, F.; Butzke, G.; Lehmann, L.; Schimko, R.

1988-11-01

186

Cigars, Cigarettes, and Adolescents  

ERIC Educational Resources Information Center

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

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

2008-01-01

187

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 of the 4,000 chemicals found in cigarette smoke are known to be harmful. Some of the most toxic chemicals

Oregon, University of

188

Monitoring the absorption of organic vapors to a solid phase extraction medium applications to detection of trace volatile organic compounds by integration of solid phase absorbents with fiber optic Raman spectroscopy  

Microsoft Academic Search

By combining fiber optic Raman spectroscopy with a C-18 solid phase extraction medium, real time in situ detection of organic vapors is demonstrated. The response of the probe is fully reversible for benzene, trichloroethylene and carbon tetrachloride vapors. Because of the high degree of selectivity afforded by Raman spectroscopy, the composition of mixtures of the vapors can also be determined

K. J. Ewing; G. Nau; T. Bilodeau; D. M. Dagenais; F. Bucholtz; I. D. Aggarwal

1997-01-01

189

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

190

Wetting phenomenon in the liquid-vapor phase coexistence of a partially miscible Lennard-Jones binary mixture.  

PubMed

We have carried out extensive equilibrium molecular dynamics simulations to study the structure and the interfacial properties in the liquid-vapor phase coexistence of partially miscible binary Lennard-Jones mixtures. By analyzing the structural properties as a function of the miscibility parameter, alpha, we found that at relatively low temperatures the system separates forming a liquid A-liquid B interface in coexistence with the vapor phase. At higher temperatures and, 0< alpha < or =0.5 , we found a temperature range, T*w (alpha) < or =T*< T*Cons (alpha) , where the liquid phases are wet by the vapor phase. Here, T*w (alpha) represents the wetting transition temperature and T*Cons (alpha) is the consolute temperature of the mixture. However, for 0.5< alpha <1 , no wetting phenomenon occurs. For the particular value, alpha=0.25 , we analyzed quantitatively the T* versus rho* , and P* versus T* phase diagrams and found, T*c approximately 1.25 , and T*Cons approximately 1.25 . We also studied quantitatively, as a function of temperature, the surface tension and the adsorption of molecules at the liquid-liquid interface. It was found that the adsorption shows a jump from a finite negative value up to minus infinity, when the vapor wets the liquid phases, suggesting that the wetting transition is of first order. The calculated phase diagram, together with the wetting phenomenon, strongly suggests the existence of a tricritical point. These results agree well with some experiments carried out in fluid binary mixtures. PMID:15600622

Díaz-Herrera, Enrique; Moreno-Razo, J Antonio; Ramírez-Santiago, Guillermo

2004-11-01

191

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

192

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

193

A model of laser ablation with temperature-dependent material properties, vaporization, phase explosion and plasma shielding  

NASA Astrophysics Data System (ADS)

Laser ablation of metals using nanosecond pulses occurs mainly due to vaporization. However, at high fluences, when the target is heated close to its critical temperature, phase explosion also occurs due to homogeneous nucleation. Due to a wide variation in target temperature, the material properties also show a considerable variation. In this paper, a model of laser ablation is presented that considers vaporization and phase explosion as mechanisms of material removal and also accounts for the variation in material properties up to critical temperature using some general and empirical theories. In addition, plasma shielding due to inverse bremsstrahlung and photo-ionization is considered. The model predicts accurately (within 5 %) the phase explosion threshold fluence of Al. The predictions of ablation depth by the model are in reasonable agreement with experimental measurements at low fluences. Whereas, the degree of error marginally increases at high laser fluences.

Marla, Deepak; Bhandarkar, Upendra V.; Joshi, Suhas S.

2014-07-01

194

NMR study of the vapor phase contribution to diffusion in partially filled silica glasses with nanometer and micrometer pores.  

PubMed

The contribution of the vapor phase to molecular diffusion in porous silica glasses with nanometer (Vycor) and micrometer (VitraPor#5) pores partially filled with water (polar) or cyclohexane (nonpolar) was investigated with the aid of field-gradient NMR diffusometry. Due to the vapor phase, the effective diffusion coefficient of cyclohexane filling micrometer pores (VitraPor#5) increased up to 10 times relative to the value in bulk liquid upon reduction of the pore space filling factor. On the other hand, the effective diffusion coefficient of water first decreases and then increases when the liquid content is reduced. The dependence of the effective diffusion coefficient on the pore filling factor is strongly related to the pore dimension. A general two-phase exchange model is presented that is well accounting for all experimental diffusion features. PMID:15833628

Ardelean, Ioan; Farrher, German; Mattea, Carlos; Kimmich, Rainer

2005-02-01

195

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

196

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

197

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

198

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

199

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

200

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

NASA Astrophysics Data System (ADS)

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

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

2001-10-01

201

Semipolar GaN growth on patterned sapphire substrates by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

This paper presents the growth of thick semipolar {10-11}, {11-22}, and {20-21} GaN layers on n, r, and {22-43} patterned sapphire substrates (PSSs), respectively, by hydride vapor phase epitaxy. The reduction rate of the dislocation density varied with growth planes. For {10-11} GaN layers, the dislocation density drastically decreased at over 100 ?m, which was as fast the reduction rate as in the case of the c-plane. It was revealed that the reduction rate of the dislocation density could be controlled by the proper selection of the growth plane. We obtained a freestanding GaN of 2 inch diameter. Thick GaN growth led to the self-separation of the GaN layer from the PSS during cooling process. The separation plane formed at the interface between GaN and PSS, which is different from the case of a conventional c-plane GaN/sapphire. The separationability of the GaN layer from the PSS depended on the selective growth area of the sapphire sidewall.

Yamane, K.; Okada, N.; Furuya, H.; Tadatomo, K.

2013-03-01

202

Vapor phase reactions in polymerization plasma for divinylsiloxane-bis-benzocyclobutene film deposition  

SciTech Connect

Vapor phase reactions in plasma polymerization of divinylsiloxane-bis-benzocyclobutene (DVS-BCB) low-k film depositions on 300 mm wafers were studied using mass spectrometry, in situ Fourier transform infrared, and a surface wave probe. Polymerization via Diels-Alder cycloaddition reaction was identified by the detection of the benzocyclohexene group. Hydrogen addition and methyl group desorption were also detected in DVS-BCB monomer and related large molecules. The dielectric constant k of plasma polymerized DVS-BCB with a plasma source power range up to 250 W was close to {approx}2.7 of thermally polymerized DVS-BCB, and increased gradually over 250 W. The electron density at 250 W was about 1.5x10{sup 10} cm{sup -3}. The increase of the k value at higher power was explained by the decrease of both large molecular species via multistep dissociation and incorporation of silica components into the polymer. It was found that the reduction of electron density as well as precursor residence time is important for the plasma polymerization process to prevent the excess dissociation of the precursor.

Kinoshita, Keizo; Nakano, Akinori; Kawahara, Jun; Kunimi, Nobutaka; Hayashi, Yoshihiro; Kiso, Osamu; Saito, Naoaki; Nakamura, Keiji; Kikkawa, Takamaro [MIRAI, Association of Super-Advanced Electronics Technologies (ASET), AIST-Tsukuba-West, Tsukuba, Ibaraki 305-8569 (Japan); MIRAI, Advanced Semiconductor Research Center (ASRC), National Institute of Advanced Industrial Science and Technology (AIST), AIST-Tsukuba-West, Tsukuba, Ibaraki 305-8569 (Japan); Energy Electronics Institute, AIST, AIST-Tsukuba-Central, Tsukuba, Ibaraki 305-8568 (Japan); Department of Electrical Engineering, Chubu University, 1200 Matsumoto, Kasugai, Aichi 487-8501 (Japan); Research Center for Nanodevices and Systems, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8527 (Japan)

2006-11-15

203

Vapor-phase polymerization of nanofibrillar poly(3,4-ethylenedioxythiophene) for supercapacitors.  

PubMed

Nanostructures of the conducting polymer poly(3,4-ethylenedioxythiophene) with large surface areas enhance the performance of energy storage devices such as electrochemical supercapacitors. However, until now, high aspect ratio nanofibers of this polymer could only be deposited from the vapor-phase, utilizing extrinsic hard templates such as electrospun nanofibers and anodized aluminum oxide. These routes result in low conductivity and require postsynthetic template removal, conditions that stifle the development of conducting polymer electronics. Here we introduce a simple process that overcomes these drawbacks and results in vertically directed high aspect ratio poly(3,4-ethylenedioxythiophene) nanofibers possessing a high conductivity of 130 S/cm. Nanofibers deposit as a freestanding mechanically robust film that is easily processable into a supercapacitor without using organic binders or conductive additives and is characterized by excellent cycling stability, retaining more than 92% of its initial capacitance after 10,000 charge/discharge cycles. Deposition of nanofibers on a hard carbon fiber paper current collector affords a highly efficient and stable electrode for a supercapacitor exhibiting gravimetric capacitance of 175 F/g and 94% capacitance retention after 1000 cycles. PMID:24490747

D'Arcy, Julio M; El-Kady, Maher F; Khine, Pwint P; Zhang, Linghong; Lee, Sun Hwa; Davis, Nicole R; Liu, David S; Yeung, Michael T; Kim, Sung Yeol; Turner, Christopher L; Lech, Andrew T; Hammond, Paula T; Kaner, Richard B

2014-02-25

204

Radiation-induced defects in GaN bulk grown by halide vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Defects induced by electron irradiation in thick free-standing GaN layers grown by halide vapor phase epitaxy were studied by deep level transient spectroscopy. In as-grown materials, six electron traps, labeled D2 (EC-0.24 eV), D3 (EC-0.60 eV), D4 (EC-0.69 eV), D5 (EC-0.96 eV), D7 (EC-1.19 eV), and D8, were observed. After 2 MeV electron irradiation at a fluence of 1 × 1014 cm-2, three deep electron traps, labeled D1 (EC-0.12 eV), D5I (EC-0.89 eV), and D6 (EC-1.14 eV), were detected. The trap D1 has previously been reported and considered as being related to the nitrogen vacancy. From the annealing behavior and a high introduction rate, the D5I and D6 centers are suggested to be related to primary intrinsic defects.

Duc, Tran Thien; Pozina, Galia; Son, Nguyen Tien; Janzén, Erik; Ohshima, Takeshi; Hemmingsson, Carl

2014-09-01

205

Environmentally Compatible Vapor-Phase Corrosion Inhibitor for Space Shuttle Hardware  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

206

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

207

Magnetic Resonance Imaging of Nonaqueous Phase Liquid During Soil Vapor Extraction in Heterogeneous Porous Media  

NASA Astrophysics Data System (ADS)

Soil vapor extraction (SVE) is commonly used to remediate nonaqueous phase liquids (NAPLs) from the vadose zone. This research 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 non-destructive, 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 mm) only, fine grains (32-63 mm) 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 or fine grain silica gel. In the heterogeneous column the volatilization front in the core lagged behind the shell because flow was through the shell and decane in the core diffused outward to the shell. When decane saturation in fine grains was above residual saturation, decane volatilization occurred near the inlet, and decane in the core moved to the shell to replenish volatilized decane. These results indicate that NAPL trapped in low permeability zones can spread to replenish areas where NAPL is lost due to SVE. However, when residual NAPL saturation is reached spreading no longer occurs and diffusion limits removal from low permeability zones.

Chu, Y.; Werth, C. J.; Valocchi, A. J.; Webb, A.

2002-12-01

208

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

209

The behavioral economics of cigarette smoking: The concurrent presence of a substitute and an independent reinforcer.  

PubMed

The present study examined the consumption of cigarettes and two alternative reinforcers in dependent smokers. Cigarette price (response requirement) increased across sessions while alternatives were available at a fixed price in four phases of availability: (1). cigarettes alone; (2). cigarettes and nicotine gum; (3). cigarettes and money; and (4). cigarettes, nicotine gum, and money. Cigarette consumption decreased with increasing price throughout. In the cigarette and nicotine gum phase, nicotine gum consumption increased with cigarette price, indicating nicotine gum to be a substitute for cigarettes. In the cigarette and money phase, money consumption increased slightly with cigarette price, indicating money to be an independent reinforcer for cigarettes. When all three reinforcers were present, money again served as an independent reinforcer. During this phase, nicotine gum consumption increased marginally, but the small magnitude of increase suggests that nicotine gum functioned as an independent reinforcer rather than a substitute. Cigarette consumption decreased modestly when nicotine gum was available, and to a larger extent when money or both alternatives were available. The results highlight the potential for an independent reinforcer such as money to be more effective at reducing drug use than a pharmacological substitute. PMID:12658074

Johnson, M W; Bickel, W K

2003-03-01

210

Iron isotope fractionation between liquid and vapor phases of iron pentacarbonyl.  

PubMed

Iron isotope fractionation between liquid and vapor iron pentacarbonyl was measured in a closed system at approximately 0 and approximately 21 degrees C to determine if Fe isotope analysis of iron pentacarbonyl vapor is viable using electron-impact, gas-source mass spectrometry. At the 2sigma level, there is no significant Fe isotope fractionation between vapor and liquid under conditions thought to reflect equilibrium. Experiments at approximately 0 degrees C indicate iron pentacarbonyl vapor is approximately 0.05 per mil (per thousand) greater in (56)Fe/(54)Fe than liquid iron pentacarbonyl, which is just resolvable at the 1sigma level. Partial decomposition of iron pentacarbonyl vapor or liquid to an iron oxide or iron metal shows that significant isotopic fractionation occurs, where the decomposed product has a lower (56)Fe/(54)Fe ratio as compared to the starting iron pentacarbonyl. It follows that methods to decompose iron pentacarbonyl must be quantitative to obtain accurate isotope values. PMID:19071272

Wiesli, René A; Beard, Brian L; Braterman, Paul S; Johnson, Clark M; Saha, Susanta K; Sinha, Mahadeva P

2007-01-15

211

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

212

Water Sorption and Vapor-Phase Deuterium Exchange Studies on Methemoglobin CC, SC, SS, AS, and AA  

PubMed Central

Five hemoglobins whose genetic relationship to one another involves one set of alleles, hemoglobins CC, SC, SS, AS, and AA, were studied in the Met form. Two different investigations were conducted at 28°C on these methemoglobins within a McBain gravimetric sorption system: sorption of H2O vapor and vapor-phase deuterium-hydrogen exchange. For each of the five samples there was close agreement between the per cent hydration of polar sites as determined from sorption studies and the maximum per cent of labile hydrogens that were exchanged during the vapor-phase deuterium exchange study. Both studies measured a slight increase in the number of polar sites accessible to H2O or D2O vapor for those samples in which the substituent in the sixth position from the N-terminus of the two ?-chains had a positively charged side chain and a slight decrease for those in which the substituent had a negatively charged side chain. The in-exchange of deuterium for hydrogen occurred at a faster observed rate than the out-exchange of hydrogen for deuterium. PMID:5030563

Killion, Philip J.; Cameron, Bruce F.

1972-01-01

213

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

214

Comparison of hole traps in n-GaN grown by hydride vapor phase epitaxy, metal organic chemical vapor deposition, and epitaxial lateral overgrowth  

NASA Astrophysics Data System (ADS)

Optical deep level spectroscopy (ODLTS) and microcathodoluminescence (MCL) spectra were measured for a large group of n-GaN samples grown via metalorganic chemical vapor deposition (MOCVD), epitaxial lateral overgrowth (ELOG), or hydride vapor phase epitaxy (HVPE). In the MOCVD and ELOG samples, the ionization energy of dominant hole traps H1 was dependent on the excitation conditions and was ˜0.9 eV for high injection levels providing saturation of the ODLTS peak magnitude. The trap concentration increased with increasing Si donor concentration and correlated with the yellow band intensity in the MCL spectra. For the HVPE samples, the hole trap spectra were radically different from the MOCVD case: four hole traps—H2, H3, H4, and H5—with activation energies of 0.55, 0.65, 0.85, and 1.2 eV, respectively, were detected. In the MCL spectra, a broad green band that peaked near 2.5 eV was observed in addition to the usual yellow luminescence near 2.3 eV. This green band was attributed to the transitions involving the H4 hole traps. Possible identities of the hole traps detected in the MOCVD/ELOG and HVPE samples are discussed.

Polyakov, A. Y.; Lee, I.-H.; Smirnov, N. B.; Govorkov, A. V.; Kozhukhova, E. A.; Pearton, S. J.

2011-06-01

215

Vapor-phase interactions and diffusion of organic solvents in the unsaturated zone  

USGS Publications Warehouse

This article presents an analysis of the interactions and static movement of 37 organic solvents as vapors through the unsaturated soil zone. The physicochemical interactions of the organic vapors with unsaturated soil materials were emphasized with focus on diffusive, and adsorptive interactions. Fick's Law and porous media diffusion coefficients for most of the solvent vapors were either compiled or estimated; coefficients were not available for some of the fluorinated solvents. The adsorption of some of the solvent vapors by silica was concluded to be due to hydrogen bond formation with surface silanol groups. Heats of adsorption data for different adsorbents were also compiled. There were very few data on the adsorption of these solvent vapors by soils, but it appears that the magnitude of adsorption of nonpolar solvents is reduced as the relative humidity of the vapor-solid system is increased. Consequently, the interaction of the vapors may then separated into two processes; (1) gas-water partitioning described by Henry's Law constants, and (2) solid-water adsorption coefficients which may be estimated from liquid-solid partition coefficients (Kd values). ?? 1990 Springer-Verlag New York Inc.

Roy, W. R.; Griffin, R. A.

1990-01-01

216

Separation of butane and xylene isomers with MFI-type zeolitic membrane synthesized by a vapor-phase transport method  

Microsoft Academic Search

MFI-type zeolitic membranes were prepared by a vapor-phase transport (VPT) method on porous ?-alumina flat disks. Single- and mixed-gas permeation measurements of butane isomers were performed in the temperature range of 300–375K. The separation factor was always greater than the ideal selectivity. This result is explained by the preferential adsorption of n-butane on MFI in the binary system.The pervaporation tests

Takaaki Matsufuji; Norikazu Nishiyama; Masahiko Matsukata; Korekazu Ueyama

2000-01-01

217

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

218

In situ observation of ellipsometry monolayer oscillations of metalorganic vapor-phase epitaxy-grown III–V compound materials  

Microsoft Academic Search

Oscillations of the ellipsometry signal were clearly seen during metalorganic vapor-phase epitaxy (MOVPE) of III–V materials under high sample rotation at 1400rpm. The ellipsometric signal oscillated at a period corresponding to 1 monolayer of MOVPE growth. Agreement was excellent between growth rate data from the oscillation period and that from thickness measurements after growth (deviation: <1%). Oscillations correlated with the

Jeong-Sik Lee; Shigeo Sugou; Yasuaki Masumoto

2000-01-01

219

Optimising uniformity of InAs\\/(InGaAs)\\/GaAs quantum dots grown by metal organic vapor phase epitaxy  

Microsoft Academic Search

A route towards optimisation of uniformity and density of InAs\\/(InGaAs)\\/GaAs quantum dots grown by metal organic vapor phase epitaxy (MOVPE) through successive variations of the growth parameters is reported. It is demonstrated that a key parameter in obtaining a high density of quantum dots is the V\\/III ratio, a fact which was shown to be valid when either AsH3 (arsine)

Linda Höglund; E. Petrini; C. Asplund; H. Malm; J. Y. Andersson; P. O. Holtz

2006-01-01

220

Source proximity reflected in spatial and temporal variability in particle and vapor phase Hg concentrations in Detroit, MI  

Microsoft Academic Search

Vapor-phase Hg, particulate Hg, and total suspended particulate matter were collected from 1 April 1996–31 October 1996 at two sites located in industrial areas of northeast and southwest Detroit, at a suburban residential site 2km west of Detroit, and at a rural site 60km west of Detroit as part of a larger study designed to assess the Hg cycling within

Amy E. Gildemeister; Joseph Graney; Gerald J. Keeler

2005-01-01

221

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

Microsoft Academic Search

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

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

2009-01-01

222

An interrogation of the zinc oxide–gallium oxide phase space by plasma enhanced chemical vapor deposition  

Microsoft Academic Search

Polycrystalline metal oxide thin films were deposited by mixing combinations of diethylzinc and trimethylgallium into an oxygen plasma. Plasma-enhanced chemical vapor deposition was shown to be a flexible tool for materials exploration, as the entire zinc–gallium-oxide phase space was explored by simply altering precursor flow rates. Film identification was performed using measurements of intrinsic optical properties as well as X-ray

J. J. Robbins; C. Fry; C. A. Wolden

2004-01-01

223

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

224

Indirect Determination of Electronic Transition Frequencies of Coronene, Triphenylene and 1,2,5,6Dibenzanthracene in the Vapor Phase  

Microsoft Academic Search

Frequencies of absorption band maxima for the first two electronic singlet transitions of coronene, triphenylene and 1,2,5,6-dibenzanthracene in vapor phase were calculated indirectly from solution spectral data. The calculations were based on two different models: the first one was a linear correlation between the solution absorption frequencies in nonpolar solvents and the solvent refractive indices. The accuracy of both methods

R. G. E. Morales; G. Traverso

1982-01-01

225

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

PubMed

Salmonella contamination on raw shrimp is a big food safety concern in the United States currently. This research evaluated the inhibition 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), inoculated onto the surface of raw shrimp, treated with vapor phase thymol at 3 levels (0, 0.8, and 1.6 mg/L), or MA (59.5% CO2 + 39.5% N2 + 1% O2 ), both alone and in combination, at 3 temperatures (8, 12, and 16 ºC), were determined. Lag time and maximum growth rate of Salmonella spp. under each treatment were obtained using Baranyi and Roberts models. Results indicated that both vapor phase thymol and MA treatments alone inhibited the growth potential of Salmonella spp. effectively, extending the lag time by 10% to 100% and reducing the maximum growth rate by 14% to 71% compared with controlled samples at experimental temperatures (8, 12, and 16 ºC). Combination treatments of vapor phase thymol and MA exhibited greater inhibition effectiveness than each individual treatment and a synergistic antimicrobial effectiveness could be observed on the lag time extension. To the maximum, at 12 ºC, lag time of Salmonella spp. was extended 59.6% more by the combination treatment of 0.8 mg/L thymol + MA (36.97 h) than those effects combined from 0.8 mg/L thymol treatment and MA treatment alone (23.16 h in total). This combination strategy could be potentially utilized for Salmonella inhibition during the long distance and temperature-abused raw shrimp import process. PMID:23574427

Zhou, Siyuan; Sheen, Shiowshuh; Pang, Yu-Hsin; Liu, LinShu; Yam, Kit L

2013-05-01

226

Thermal effects on light-emission properties of GaN LEDs grown by metal-organic vapor phase epitaxy  

Microsoft Academic Search

Photoluminescence (PL) spectra of GaN layers grown on sapphire substrates by metal-organic vapor phase epitaxy (MOVPE) were observed at temperatures from RT to 500K. The spectra include the near-band-edge emission (NBE) and yellow luminescence (YL). The peak energy of the NBE is shifted towards lower energy with increasing observed temperature. UV light-emitting diodes (LEDs) utilizing band-gap narrowing due to thermal

Tohru Honda; Toshiaki Kobayashi; Shinichi Egawa; Masaru Sawada; Koichi Sugimoto; Taichi Baba

2007-01-01

227

Synthesis of narrow band-gap III-V semiconductors using metal-organic vapor phase epitaxy  

Microsoft Academic Search

The synthesis of narrow band gap materials in particular InAs, GaSb and InSb has been studied using metal-organic vapor phase epitaxy (MOVPE). Typically, for device applications these materials are grown on SI GaAs substrates. The integration of these materials with GaAs substrates through direct epitaxial growth is plagued by the high density of defects that are formed due to the

Smita Jha

2010-01-01

228

Perceived efficacy of e-cigarettes versus nicotine replacement therapy among successful e-cigarette users: a qualitative approach  

PubMed Central

Background Nicotine is widely recognized as an addictive psychoactive drug. Since most smokers are bio-behaviorally addicted, quitting can be very difficult and is often accompanied by withdrawal symptoms. Research indicates that nicotine replacement therapy (NRT) can double quit rates. However, the success rate for quitting remains low. E-cigarettes (electronic cigarettes) are battery-powered nicotine delivery devices used to inhale doses of vaporized nicotine from a handheld device similar in shape to a cigarette without the harmful chemicals present in tobacco products. Anecdotal evidence strongly suggests that e-cigarettes may be effective in helping smokers quit and preventing relapse, but there have been few published qualitative studies, especially among successful e-cigarette users, to support this evidence. Methods Qualitative design using focus groups (N?=?11); 9 men and 2 women. Focus groups were conducted by posing open-ended questions relating to the use of e-cigarettes, comparison of effectiveness between NRTs and e-cigarettes, barriers to quitting, and reasons for choosing e-cigarettes over other methods. Results Five themes emerged that describe users’ perceptions of why e-cigarettes are efficacious in quitting smoking: 1) bio-behavioral feedback, 2) social benefits, 3) hobby elements, 4) personal identity, and 5) distinction between smoking cessation and nicotine cessation. Additionally, subjects reported their experiences with NRTs compared with e-cigarettes, citing negative side effects of NRTs and their ineffectiveness at preventing relapse. Conclusion These findings suggest tobacco control practitioners must pay increased attention to the importance of the behavioral and social components of smoking addiction. By addressing these components in addition to nicotine dependence, e-cigarettes appear to help some tobacco smokers transition to a less harmful replacement tool, thereby maintaining cigarette abstinence. PMID:23497603

2013-01-01

229

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

230

Polycrystalline indium phosphide on silicon by indium assisted growth in hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Polycrystalline InP was grown on Si(001) and Si(111) substrates by using indium (In) metal as a starting material in hydride vapor phase epitaxy (HVPE) reactor. In metal was deposited on silicon substrates by thermal evaporation technique. The deposited In resulted in islands of different size and was found to be polycrystalline in nature. Different growth experiments of growing InP were performed, and the growth mechanism was investigated. Atomic force microscopy and scanning electron microscopy for morphological investigation, Scanning Auger microscopy for surface and compositional analyses, powder X-ray diffraction for crystallinity, and micro photoluminescence for optical quality assessment were conducted. It is shown that the growth starts first by phosphidisation of the In islands to InP followed by subsequent selective deposition of InP in HVPE regardless of the Si substrate orientation. Polycrystalline InP of large grain size is achieved and the growth rate as high as 21 ?m/h is obtained on both substrates. Sulfur doping of the polycrystalline InP was investigated by growing alternating layers of sulfur doped and unintentionally doped InP for equal interval of time. These layers could be delineated by stain etching showing that enough amount of sulfur can be incorporated. Grains of large lateral dimension up to 3 ?m polycrystalline InP on Si with good morphological and optical quality is obtained. The process is generic and it can also be applied for the growth of other polycrystalline III-V semiconductor layers on low cost and flexible substrates for solar cell applications.

Metaferia, Wondwosen; Sun, Yan-Ting; Pietralunga, Silvia M.; Zani, Maurizio; Tagliaferri, Alberto; Lourdudoss, Sebastian

2014-07-01

231

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

232

Vapor-liquid phase coexistence and transport properties of two-dimensional oligomers  

NASA Astrophysics Data System (ADS)

Grand-canonical transition-matrix Monte Carlo and histogram reweighting techniques are used herein to study the vapor-liquid coexistence properties of two-dimensional (2D) flexible oligomers with varying chain lengths (m = 1-8). The phase diagrams of the various 2D oligomers follow the correspondence state (CS) principle, akin to the behavior observed for bulk oligomers. The 2D critical density is not influenced by the oligomer chain length, which contrasts with the observation for the bulk oligomers. Line tension, calculated using Binder's formalism, in the reduced plot is found to be independent of chain length in contrast to the 3D behavior. The dynamical properties of 2D fluids are evaluated using molecular dynamics simulations, and the velocity and pressure autocorrelation functions are investigated using Green-Kubo (GK) relations to yield the diffusion and viscosity. The viscosity determined from 2D non-equilibrium molecular dynamics simulation is compared with the viscosity estimated from the GK relations. The GK relations prove to be reliable and efficient for the calculation of 2D transport properties. Normal diffusive regions are identified in dense oligomeric fluid systems. The influence of molecular size on the diffusivity and viscosity is found to be diminished at specific CS points for the 2D oligomers considered herein. In contrast, the viscosity and diffusion of the 3D bulk fluid, at a reduced temperature and density, are strongly dependent on the molecular size at the same CS points. Furthermore, the viscosity increases and the diffusion decreases multifold in the 2D system relative to those in the 3D system, at the CS points.

Patra, Tarak K.; Hens, Abhiram; Singh, Jayant K.

2012-08-01

233

Solid-State, Dye-Labeled DNA Detects Volatile Compounds in the Vapor Phase  

PubMed Central

This paper demonstrates a previously unreported property of deoxyribonucleic acid—the ability of dye-labeled, solid-state DNA dried onto a surface to detect odors delivered in the vapor phase by changes in fluorescence. This property is useful for engineering systems to detect volatiles and provides a way for artificial sensors to emulate the way cross-reactive olfactory receptors respond to and encode single odorous compounds and mixtures. Recent studies show that the vertebrate olfactory receptor repertoire arises from an unusually large gene family and that the receptor types that have been tested so far show variable breadths of response. In designing biomimetic artificial noses, the challenge has been to generate a similarly large sensor repertoire that can be manufactured with exact chemical precision and reproducibility and that has the requisite combinatorial complexity to detect odors in the real world. Here we describe an approach for generating and screening large, diverse libraries of defined sensors using single-stranded, fluorescent dye–labeled DNA that has been dried onto a substrate and pulsed with brief exposures to different odors. These new solid-state DNA-based sensors are sensitive and show differential, sequence-dependent responses. Furthermore, we show that large DNA-based sensor libraries can be rapidly screened for odor response diversity using standard high-throughput microarray methods. These observations describe new properties of DNA and provide a generalized approach for producing explicitly tailored sensor arrays that can be rationally chosen for the detection of target volatiles with different chemical structures that include biologically derived odors, toxic chemicals, and explosives. PMID:18215112

White, Joel; Truesdell, Kathleen; Williams, Lloyd B; AtKisson, Mary S; Kauer, John S

2008-01-01

234

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

235

Desalination-of water by vapor-phase transport through hydrophobic nanopores  

E-print Network

We propose a new approach to desalination of water whereby a pressure difference across a vapor-trapping nanopore induces selective transport of water by isothermal evaporation and condensation across the pore. Transport ...

Lee, Jongho

236

The development of the performance measuring system for the phase change heat transport device-heat pipe, vapor chamber and defrost plate  

Microsoft Academic Search

A multipurpose of the performance measuring system for the phase change heat transport device such as heat pipe, vapor chamber and defrost plate was designed in this study. The characteristic of this measuring system was using thermal electrical chip (T.E.C.) as the condenser. This paper also present experimental measurement of performance of a vapor chamber (VC), heat pipe and defrost

Wei-Keng Lin; Chen-I Chao; Y. M. Tzou; H. G. H. Chang; Paul Wang

2011-01-01

237

Asthma and cigarette smoking  

Microsoft Academic Search

ABSTRACT: In most,developed,countries y25% of adults with asthma,are current cigarette smokers. Asthma and active cigarette smoking,interact to cause more,severe symptoms, accelerated decline in lung function, and impaired short-term therapeutic response to corticosteroids. Cigarette smoking may modify inflammation that is associated with asthma, although,there is limited published data on airway pathology,in smokers,with asthma. To date, the evidence points towards a combination

N. C. Thomson; R. Chaudhuri; E. Livingston

2004-01-01

238

Smoking stimuli from the terminal phase of cigarette consumption may not be cues for smoking in healthy smokers  

Microsoft Academic Search

Background  Stimuli from the terminal phase of smoke or drug intake are paired with drug effect but have surprisingly low cue reactivity.\\u000a Smoking terminal stimuli were compared to cues under conditions of different perceived smoke intake to probe whether (1) terminal\\u000a stimuli are only weak cues, (2) any effect is an artifact of rigid test conditions, and (3) terminal stimuli have

Ronald F. Mucha; Paul Pauli; Markus Weber; Markus Winkler

2008-01-01

239

A Method to Use Modis Water Vapor Products For Correction of Atmospheric-Induced Phase in Interferogram  

NASA Astrophysics Data System (ADS)

DInSAR is a major space-geodetic technique widely used in the study of earth surface deformation. A major source of phase errors in DInSAR technique is heterogeneous phase delay caused mainly by variation of water vapors in troposphere, which is a factor limiting applications of DInSAR mainly to arid areas. This paper presents study results of three methods to correct atmospheric phase errors in DInSAR interferograms formed by TerraSAR-X images. The first method is the use of wet delay derived directly from MODIS precipitable water vapor product. The second method employs ground-based meteorological data to calibrate MODIS PWV before computing phase delays. The third method improves the second method by estimating the expected MODIS PWV value at the time of the TerraSAR-X image acquisitions which over the Bangkok test area is 5 hour earlier than that of MODIS. The time-shifted linear fit model along with the IDW interpolation is used to estimate more realistic phase delays over entire imaging area. From the study of this tropical test area, this time-corrected method provides best results while the second method also achieves a significantly better result than those obtained from direct use of MODIS PWV data.

Keeratikasikorn, Chaiyapon; Trisirisatayawong, Itthi

2011-01-01

240

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

241

Vapor-phase activities of cinnamon, thyme, and oregano essential oils and key constituents against foodborne microorganisms.  

PubMed

The aim of the study presented here was to gain knowledge about the vapor-phase antimicrobial activity of selected essential oils and their major putatively active constituents against a range of foodborne bacterial and fungal strains. In a first step, the vapor-phase antimicrobial activities of three commercially available essential oils (EOs)-cinnamon (Cinnamomum zeylanicum), thyme (Thymus vulgaris), and oregano (Origanum vulgare)-were evaluated against a wide range of microorganisms, including Gram-negative bacteria (Escherichia coli, Yersinia enterocolitica, Pseudomonas aeruginosa, and Salmonella choleraesuis), Gram-positive bacteria (Listeria monocytogenes, Staphylococcus aureus, Bacillus cereus, and Enterococcus faecalis), molds (Penicillium islandicum and Aspergillus flavus), and a yeast (Candida albicans). The minimum inhibitory concentrations (MICs) were generally lower for oregano EO than for the thyme and cinnamon EOs, especially against the relatively resistant Gram-negative. The persistence of the EOs' antimicrobial activities over time was assessed, and changes in the composition of the atmosphere they generated over time were determined using single-drop microextraction (SDME) in combination with gas chromatography-mass spectrometry (GC-MS) and subsequent analysis of the data by principal component analysis (PCA). More relevant chemicals were selected. In addition, the vapor-phase activities of putatively key constituents of the oils were screened against representative Gram-positive (L. monocytogenes) and Gram-negative (S. choleraesuis) bacteria, a mold (A. flavus), and a yeast (C. albicans). Of the tested compounds, cinnamaldehyde, thymol, and carvacrol showed the strongest antimicrobial effectiveness, so their MICs, defined as the minimum vapor concentrations that completely inhibited detectable growth of the microorganisms, were calculated. To check for possible interactions between components present in the EOs, cinnamon EO was fortified with cinnamaldehyde and thyme EO with thymol, and then the antimicrobial activities of the fortified oils were compared to those of the respective unfortified EOs using fractional inhibitory concentration (FIC) indices and by plotting inhibition curves as functions of the vapor-phase concentrations. Synergistic effects were detected for cinnamaldehyde on A. flavus and for thymol on L. monocytogenes, S. choleraesuis, and A. flavus. In all other cases the fortification had additive effects, except for cinnamaldehyde's activity against S. choleraesuis, for which the effect was antagonistic. Finally, various microorganisms were found to cause slight changes over time to the atmospheres generated by all of the EOs (fortified and unfortified) except the fortified cinnamon EO. PMID:17488023

López, Patricia; Sanchez, Cristina; Batlle, Ramón; Nerín, Cristina

2007-05-30

242

Selective area metal-organic vapor-phase epitaxy of InN, GaN and InGaN covering whole composition range  

Microsoft Academic Search

To investigate mask effects on InGaN selective area metal-organic vapor-phase epitaxy (SA-MOVPE), in-plane thickness profiles of InGaN were investigated with various indium contents covering between InN and GaN. A numerical simulation employing vapor-phase diffusion (VPD) model was also carried out for the quantitative analysis of VPD effect. At the growth temperatures of 650 and 700°C, the indium content in the

Tomonari Shioda; Masakazu Sugiyama; Yukihiro Shimogaki; Yoshiaki Nakano

2009-01-01

243

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

SciTech Connect

Co-produced water from the oil and gas industry accounts for a significant waste stream in the United States. Produced waters typically contain a high total dissolved solids content, dissolved organic constituents such as benzene and toluene, an oil and grease component as well as chemicals added during the oil-production process. It has been estimated that a total of 14 billion barrels of produced water were generated in 2002 from onshore operations (Veil, 2004). Although much of this produced water is disposed via reinjection, environmental and cost considerations can make surface discharge of this water a more practical means of disposal. In addition, reinjection is not always a feasible option because of geographic, economic, or regulatory considerations. In these situations, it may be desirable, and often necessary from a regulatory viewpoint, to treat produced water before discharge. It may also be feasible to treat waters that slightly exceed regulatory limits for re-use in arid or drought-prone areas, rather than losing them to reinjection. A previous project conducted under DOE Contract DE-AC26-99BC15221 demonstrated that surfactant modified zeolite (SMZ) represents a potential treatment technology for produced water containing BTEX. Laboratory and field experiments suggest that: (1) sorption of benzene, toluene, ethylbenzene and xylenes (BTEX) to SMZ follows linear isotherms in which sorption increases with increasing solute hydrophobicity; (2) the presence of high salt concentrations substantially increases the capacity of the SMZ for BTEX; (3) competitive sorption among the BTEX compounds is negligible; and, (4) complete recovery of the SMZ sorption capacity for BTEX can be achieved by air sparging the SMZ. This report summarizes research for a follow on project to optimize the regeneration process for multiple sorption/regeneration cycles, and to develop and incorporate a vapor phase bioreactor (VPB) system for treatment of the off-gas generated during air sparging. To this end, we conducted batch and column laboratory SMZ and VPB experiments with synthetic and actual produced waters. Based on the results of the laboratory testing, a pilot scale study was designed and conducted to evaluate the combined SMZ/VPB process. An economic and regulatory feasibility analysis was also completed as part of the current study to assess the viability of the process for various water re-use options.

Lynn E. Katz; Kerry A. Kinney; Robert S. Bowman; Enid J. Sullivan; Soondong Kwon; Elaine B. Darby; Li-Jung Chen; Craig R. Altare

2006-01-31

244

Structure of nonpolar gallium nitride films grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

Conventional c-plane (Al, In, Ga)N optoelectronic devices suffer from deleterious polarization effects. These polarization effects can be eliminated by growing devices on alternative orientations of GaN crystals, such as {11¯00} m-plane or {112¯0} a-plane films. Previous attempts to grow nonpolar GaN by HVPE, yielded rough and faceted surfaces that were unsuitable for substrate use. This dissertation describes the structural and morphological characteristics of planar, nonpolar GaN films grown by hydride vapor phase epitaxy (HVPE). Smooth, specular a-plane GaN films were grown on r-plane sapphire substrates. While smooth enough to allow device fabrication on them, these films contained ˜1010 cm -2 dislocations and ˜105 cm-1 basal plane stacking faults. Lateral epitaxial overgrowth was developed to eliminate dislocations and stacking faults in the overgrown material, reducing local dislocation and fault densities below 5 x 106 cm -2 and 5 x 103 cm-1, respectively. Significant improvements in surface morphology and luminescence characteristics of the films resulted from the structural defect elimination. Threading dislocations were shown to be responsible for the surface morphological instability that has previously complicated the growth of planar a-plane GaN by HYPE, MBE, and MOCVD. This dissertation further describes planar m-plane GaN films and free-standing wafers that have now been produced by HVPE. Free-standing 48 mm diameter m-plane GaN wafers were grown directly on (100) gamma-LiAlO2 substrates. These wafers were largely free of bulk defects that had previously plagued m-plane GaN films grown by HVPE. Just as with their a-plane counterparts, these m-plane GaN films contained high threading dislocation and stacking fault densities. LEO of m-plane GaN films was demonstrated and found effective for reducing extended defect densities in the films. Elimination of stacking faults from the overgrown material showed that the commonly observed "slate" surface morphology is a manifestation of faulting in the crystal. Fault-free m-plane GaN exhibits step-flow-like surfaces with RMS roughness of ˜0.6 nm. In summary, smooth, high-quality a- and m-plane GaN templates can now be grown by HVPE for use in the fabrication of nonpolar nitride devices.

Haskell, Benjamin Allen

245

GaN/AlGaN HEMTs grown by hydride vapor phase epitaxy on AlN/SiC substrates  

NASA Astrophysics Data System (ADS)

GaN/AlGaN high electron mobility transistors (HEMTs) were fabricated on layer structures grown by metal organic chemical vapor deposition on hydride vapor phase epitaxy grown AlN epi-layers on 6H-SiC substrates. The presence of the AlN provides an insulating buffer for effective inter-device isolation, producing isolation currents in the 10 -9 A range. These initial HEMTs exhibit saturated drain source current of >400 mA/mm with maximum transconductance of >70 mS/mm. The devices show lower degrees of current collapse relative to more conventional HEMTs fabricated on sapphire substrates, suggesting that the lower defect density is beneficial in reducing surface state trap concentration.

LaRoche, J. R.; Luo, B.; Ren, F.; Baik, K. H.; Stodilka, D.; Gila, B.; Abernathy, C. R.; Pearton, S. J.; Usikov, A.; Tsvetkov, D.; Soukhoveev, V.; Gainer, G.; Rechnikov, A.; Dimitriev, V.; Chen, G.-T.; Pan, C.-C.; Chyi, J.-I.

2004-01-01

246

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

247

Cigarette smoking and asthma  

Microsoft Academic Search

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

C. Suppli Ulrik; P. Lange

2001-01-01

248

How Youths get Cigarettes.  

National Technical Information Service (NTIS)

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

2002-01-01

249

PATTERNS OF CIGARETTE SMOKING. PA'ITERNS OF CIGARETTE SMOKING  

E-print Network

PART I: PATTERNS OF CIGARETTE SMOKING. #12;PA'ITERNS OF CIGARETTE SMOKING Introduction This chapter traces the evolution of cigarette smoking among successive generations of American women and men during onset of wide- spread cigarette use, in the rate of diffusion of smoking among each new birth cohort

Gabrieli, John

250

Tension at the Surface: Which Phase Is More Important, Liquid or Vapor?  

PubMed Central

Tension at the surface is a most fundamental physicochemical property of a liquid surface. The concept of surface tension has widespread implications in numerous natural, engineering and biomedical processes. Research to date has been largely focused on the liquid side; little attention has been paid to the vapor—the other side of the surface, despite over 100 years of study. However, the question remains as to whether the vapor plays any role, and to what extent it affects the surface tension of the liquid. Here we show a systematic study of the effect of vapor on the surface tension and in particular, a surprising observation that the vapor, not the liquid, plays a dominant role in determining the surface tension of a range of common volatile organic solutions. This is in stark contrast to results of common surfactants where the concentration in the liquid plays the major role. We further confirmed our results with a modified adsorption isotherm and molecular dynamics simulations, where highly structured, hydrogen bonded networks, and in particular a solute depletion layer just beneath the Gibbs dividing surface, were revealed. PMID:20011532

Wang, Wei; Biswas, M. Elias; Chen, P.

2009-01-01

251

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

252

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

253

Metallic 1T phase source/drain electrodes for field effect transistors from chemical vapor deposited MoS2  

NASA Astrophysics Data System (ADS)

Two dimensional transition metal dichalcogenides (2D TMDs) offer promise as opto-electronic materials due to their direct band gap and reasonably good mobility values. However, most metals form high resistance contacts on semiconducting TMDs such as MoS2. The large contact resistance limits the performance of devices. Unlike bulk materials, low contact resistance cannot be stably achieved in 2D materials by doping. Here we build on our previous work in which we demonstrated that it is possible to achieve low contact resistance electrodes by phase transformation. We show that similar to the previously demonstrated mechanically exfoliated samples, it is possible to decrease the contact resistance and enhance the FET performance by locally inducing and patterning the metallic 1T phase of MoS2 on chemically vapor deposited material. The device properties are substantially improved with 1T phase source/drain electrodes.

Kappera, Rajesh; Voiry, Damien; Yalcin, Sibel Ebru; Jen, Wesley; Acerce, Muharrem; Torrel, Sol; Branch, Brittany; Lei, Sidong; Chen, Weibing; Najmaei, Sina; Lou, Jun; Ajayan, Pulickel M.; Gupta, Gautam; Mohite, Aditya D.; Chhowalla, Manish

2014-09-01

254

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

255

Vaporizer performance  

NASA Astrophysics Data System (ADS)

This paper examines the nature of the flow leaving a vaporizer, its dependence on the flowrates of air and kerosene fuel, the inlet air temperature, and the possible consequences for the performance of a combustor fueled by the vaporizer. A phase Doppler velocimeter was used to examine the distribution of droplet diameters, velocities of the droplets, and the liquid-fuel flux at the exit. Measurements are also reported which show the nature of the two-phase flow away from the vaporizer exits and in important regions within a combustor corresponding to a one-sixth annular sector of a reverse-flow arrangement. The distribution of droplets within the combustor was observed and photographs of the combusting flow are presented.

Liu, C. H.; Perez-Ortiz, B. M.; Whitelaw, J. H.

256

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

257

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

258

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

NASA Astrophysics Data System (ADS)

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 manganese was doped into the lattice structure, forming solid solution instead of precipitation. Magnetic property measurements revealed that the as-doped Zn1-xMnxO nanowires exhibit ferromagnetic behavior with Curie temperature around 37 K.

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

2003-11-01

259

Photoresponse properties of large-area MoS2 atomic layer synthesized by vapor phase deposition  

NASA Astrophysics Data System (ADS)

Photoresponse properties of a large area MoS2 atomic layer synthesized by vapor phase deposition method without any catalyst are studied. Scanning electron microscopy, atomic force microscopy, Raman spectrum, and photoluminescence spectrum characterizations confirm that the two-dimensional microstructures of MoS2 atomic layer are of high quality. Photoelectrical results indicate that the as-prepared MoS2 devices have an excellent sensitivity and a good reproducibility as a photodetector, which is proposed to be ascribed to the potential-assisted charge separation mechanism.

Luo, Siwei; Qi, Xiang; Ren, Long; Hao, Guolin; Fan, Yinping; Liu, Yundan; Han, Weijia; Zang, Chen; Li, Jun; Zhong, Jianxin

2014-10-01

260

Rapid solid-phase crystallization of high-rate, hot-wire chemical-vapor-deposited hydrogenated amorphous silicon  

NASA Astrophysics Data System (ADS)

Solid-phase crystallization of hydrogenated amorphous silicon thin films deposited by hot-wire (HW) and plasma-enhanced (PE) chemical vapor deposition was studied using in situ optical monitoring. HW films crystallized at least five times faster than PE films, independent of H and O concentration, deposition rate (2-110Å/s), and nanovoid density due to reduced enthalpy barriers to both nucleation and final crystallization, which may be related to the presence of larger regions of highly ordered Si in the films.

Young, David L.; Stradins, Paul; Xu, Yueqin; Gedvilas, Lynn; Reedy, Bob; Mahan, A. H.; Branz, Howard M.; Wang, Qi; Williamson, D. L.

2006-10-01

261

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

262

A GaAs metalorganic vapor phase epitaxy growth process to reduce Ge outdiffusion from the Ge substrate  

SciTech Connect

A barrier based on GaAs for controlling the Ge out diffusion has been developed by metalorganic vapor phase epitaxy. It is based on a thin GaAs layer (50 nm) grown at a low temperature ({approx_equal}500 deg. C) on top of a predeposition layer, showing that GaAs prevents the Ge diffusing when it is grown at a low temperature. Additionally, two different predeposition monolayers have been compared, concluding that when the Ga is deposited first, the diffusions across the GaAs/Ge heterointerface decrease.

Galiana, B.; Rey-Stolle, I.; Algora, C. [Instituto de Energia Solar-UPM, ETSI de Telecomunicacion, Avda. Complutense s/n, Madrid 28040 (Spain); Volz, K.; Stolz, W. [Material Sciences Center (WZMW), Philipps University of Marburg, Marburg 35032 (Germany)

2008-04-14

263

Morphological and structural evolution during thermally physical vapor phase growth of PbI2 polycrystalline thin films  

NASA Astrophysics Data System (ADS)

PbI2 polycrystalline thin films have been prepared by using a thermally physical vapor phase growth in vacuum. X-ray diffraction measurement and atomic force microscope analysis show that the structural change of the films occurs depending on growth condition. The width of the Urbach tail of the films indicates that the disordered structure inside the grains changes relying on preparation condition. It is found that the structure of the films is sensitive to growth parameter. A microstructure evolution model with respect to grain orientation is developed to explain the morphological and structural variation process during the films growth.

Sun, Hui; Zhu, Xinghua; Yang, Dingyu; Yang, Jun; Gao, Xiuying; Li, Xu

2014-11-01

264

Vapor-phase esterification of acetic acid with ethanol catalyzed by a macroporous sulfonated styrene-divinylbenzene (20%) resin  

SciTech Connect

The kinetics of the vapor-phase (85-120/sup 0/C) esterification of acetic acid with ethyl alcohol, at atmospheric pressure, catalyzed by a macroporous sulfonated styrene-divinylbenzene (DVB;20%) resin, has been studied. A simple first-order model (r = kp/sub 1/) fits experimental kinetic data properly for a constant reactants ratio. Discussion by means of L-H-H-W models shows that the rate-controlling step is the surface reaction with a single-site mechanism. The apparent activation energy is 4000 cal/mol.

Gimenez, J.; Costa, J.; Cervera, S.

1987-02-01

265

Growth and characterization of gallium nitride bulk crystals via vapor phase transport  

NASA Astrophysics Data System (ADS)

Free-standing single crystals of bulk GaN were grown via unseeded vapor phase transport at 1130°C on hexagonal BN surfaces via direct reaction of Ga with ammonia. The temperature and stability of the Ga source were critical in terms of uniform nucleation and growth. The source temperature was maintained at 1260°C to minimize a rapid reaction leading to the formation of GaN and the subsequent decomposition beneath the surface and consequent spattering of Ga. A maximum crystal growth temperature of 1130°C was determined in which the GaN growth kinetics were much greater than decomposition. The number of nucleation events was reduced and the crystal size increased by a novel nucleation technique wherein NH3 was introduced at high temperatures. The resulting crystals were either needles or platelets depending on the process variables employed. Low V/III ratios achieved via ammonia flow rates ?75sccm and/or ammonia total pressures ?430Torr favored lateral growth. The average lateral growth rate for the platelets was ˜50mum/hr; the average vertical growth rate for the needles was ˜500mum/hr. Growth rates in all other directions for each of these two morphologies were very low. Seeded growth of both needle and platelet crystals was also achieved; however, the growth rate decreased at longer times and higher pressures due to reaction with H2 from the increased decomposition of ammonia. Nitrogen dilution of ammonia reduced the amount of hydrogen generated as a result of ammonia decomposition and increased the kinetic barrier to desorption of reactants from the GaN surface and then alleviated the enhanced decomposition of GaN crystals. A 2mm x 1.5mm needle and a 2.3mm x 1.8mm x 0.3mm platelet of GaN were grown with minimal decomposition in a 66.7%NH3 + 33.3%N 2 gas mixture. Excellent crystalline quality was confirmed by Raman spectroscopy and Photoluminescence. Crystal growth using a Ga- 5at%Al source was conducted in an attempt to increase growth rate and inhibit decomposition. No notable change in growth rate was observed and hollow crystals were formed, indicating that Al promotes vertical growth under otherwise similar conditions for GaN growth. In addition, fine-grained AlN was formed within the binary Ga-Al source, thus, the supply of Al was progressively reduced. Nucleation control via addition of Si resulted in a slightly reduced number of larger crystals. X-ray Photoelectron Spectroscopy suggested that amorphous silicon nitride was formed on the BN substrate and nucleation rate was slightly reduced. Silicon was not detected within the sensitivity of Energy Dispersive Spectroscopy. Raman spectroscopy revealed insignificant amount of Si present in the crystal. Smoother surface morphology of the crystals grown in the presence of Si was observed by Scanning Electron Microscopy.

Shin, Hyunmin

266

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

267

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

268

Phase transitions in the liquid-vapor interface of dilute alloys of Bi in Ga: New experimental studies  

SciTech Connect

We report the results of measurements of x-ray reflectivity and grazing incidence x-ray diffraction from the liquid-vapor interfaces of four dilute alloys of Bi in Ga with mole fractions x{sub Bi} = 0.0032, 0.0023, 0.00037, and 0.000037. The monolayer coverage of the alloys with x{sub Bi} = 0.0023, and x{sub Bi} = 0.00037 is about 0.85 and only very slightly temperature dependent. The monolayer coverage in the lowest-concentration alloy, with x{sub Bi} = 0.000037, ranged from 0.82 at 29 C to 0.58 at 110 C. In none of these alloys, down to the lowest temperature used, 29 C, can we find any evidence for crystallization of the Bi monolayer that segregates as the outermost stratum of the liquid-vapor interface. Drawing on theoretical arguments we propose that the transitions inferred from the second-harmonic generation and plasma generation studies of dilute Bi in Ga alloys are from the liquid state to the hexatic state of the Bi monolayer. The data for the alloy with x{sub Bi} = 0.000037 suggest that near 80 C there is a disordered phase-to-disordered phase transition.

Li, Dongxu; Jiang, Xu; Yang, Bin; Rice, Stuart A. (UC)

2010-07-19

269

Source proximity reflected in spatial and temporal variability in particle and vapor phase Hg concentrations in Detroit, MI  

NASA Astrophysics Data System (ADS)

Vapor-phase Hg, particulate Hg, and total suspended particulate matter were collected from 1 April 1996-31 October 1996 at two sites located in industrial areas of northeast and southwest Detroit, at a suburban residential site 2 km west of Detroit, and at a rural site 60 km west of Detroit as part of a larger study designed to assess the Hg cycling within the urban area. Near-source short-range transport can cause large differences in pollutant concentration and deposition within a small geographic area. Hg deposition and the resulting impact on the local environment is a result not only of the ambient concentrations present, but of the chemical form and physical properties of the pollutant. All site-to-site differences in vapor phase Hg concentration were statistically significant ( p<0.05) with mean concentrations ranging from 1.6-2.8 ng m -3. The mean particulate Hg concentrations ranged from 12.0-54.0 pg m -3 with concentrations at the less industrialized sites significantly lower than those at the industrialized sites ( p<0.05). Hg associated with coarse particles (diameter?2.5 ?m) had a median daily contribution of 37% to the total (range 4-68%) in south-west Detroit vs. a median daily contribution of 20% at the rural sampling site (range 6-37%).

Gildemeister, Amy E.; Graney, Joseph; Keeler, Gerald J.

270

Phase transited and vapor-induced dual capsular system (DCS) for achieving delayed and osmotic release of cefadroxil.  

PubMed

In the present study, an intestinal pH, disintegrating and non-disintegrating dual capsular system using formaldehyde vapor and phase transition technique, respectively, was developed to achieve delayed as well as improved osmotic flow for the model drug cefadroxil. Formaldehyde vapor was used to attain gastric resistance to the outer gelatin capsule, which disintegrated at the intestinal pH to give a non-disintegrating asymmetric membrane capsule (AMC). The AMC was prepared via dry phase inversion process. The effects of different formulation variables were studied based on 2³ factorial design, namely, level of osmogen, ethylcellulose, and pore former, apart from studying the effects of varying osmotic pressure, agitation intensity, and intentional defect on drug release. Scanning electron microscopy showed an outer dense non-porous and an inner lighter porous region for the prepared asymmetric membrane. Statistical test was applied for in-vitro drug release at P?>?0.05. The best formulation in the design closely corresponded to the extra design checkpoint formulation by a similarity (f?) value of 95.28. The drug release was independent of the agitation intensity and intentional defect of the film but dependent on the osmotic pressure of the dissolution medium. The release kinetics followed zero-order, and mechanism of release was Fickian diffusion. PMID:20482448

Philip, Anil K; Philip, Betty

2011-10-01

271

Large-scale cubic InN nanocrystals by a combined solution- and vapor-phase method under silica confinement.  

PubMed

Large-scale cubic InN nanocrystals were synthesized by a combined solution- and vapor-phase method under silica confinement. Nearly monodisperse cubic InN nanocrystals with uniform spherical shape were dispersed stably in various organic solvents after removal of the silica shells. The average size of InN nanocrystals is 5.7 ± 0.6 nm. Powder X-ray diffraction results indicate that the InN nanocrystals are of high crystallinity with a cubic phase. X-ray photoelectron spectroscopy and energy-dispersive spectroscopy confirm that the nanocrystals are composed of In and N elements. The InN nanocrystals exhibit infrared photoluminescence at room temperature, with a peak energy of ~0.62 eV, which is smaller than that of high-quality wurtzite InN (~0.65-0.7 eV) and is in agreement with theoretical calculations. The small emission peak energy of InN nanocrystals, as compared to other low-cost solution or vapor methods, reveals the superior crystalline quality of our samples, with low or negligible defect density. This work will significantly promote InN-based applications in IR optoelectronic device and biology. PMID:22224725

Chen, Zhuo; Li, Yanan; Cao, Chuanbao; Zhao, Songrui; Fathololoumi, Saeed; Mi, Zetian; Xu, Xingyan

2012-01-18

272

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

273

Cigarette Ads and Youth.  

ERIC Educational Resources Information Center

Points out ways the tobacco industry markets products to youth, including paid advertisements, sponsorship of sporting events, music concerts, and magazines. Relates several focal points for smoking prevention, which include deglamorization of cigarette advertisements and making smoking socially undesirable. (LS)

Carol, Julia

1988-01-01

274

Real-Time Optical Monitoring and Simulations of Gas Phase Kinetics in InN Vapor Phase Epitaxy at High Pressure  

NASA Technical Reports Server (NTRS)

Understanding the kinetics of nucleation and coalescence of heteroepitaxial thin films is a crucial step in controlling a chemical vapor deposition process, since it defines the perfection of the heteroepitaxial film both in terms of extended defect formation and chemical integrity of the interface. The initial nucleation process also defines the film quality during the later stages of film growth. The growth of emerging new materials heterostructures such as InN or In-rich Ga(x)In(1-x)N require deposition methods operating at higher vapor densities due to the high thermal decomposition pressure in these materials. High nitrogen pressure has been demonstrated to suppress thermal decomposition of InN, but has not been applied yet in chemical vapor deposition or etching experiments. Because of the difficulty with maintaining stochiometry at elevated temperature, current knowledge regarding thermodynamic data for InN, e.g., its melting point, temperature-dependent heat capacity, heat and entropy of formation are known with far less accuracy than for InP, InAs and InSb. Also, no information exists regarding the partial pressures of nitrogen and phosphorus along the liquidus surfaces of mixed-anion alloys of InN, of which the InN(x)P(1-x) system is the most interesting option. A miscibility gap is expected for InN(x)P(1-x) pseudobinary solidus compositions, but its extent is not established at this point by experimental studies under near equilibrium conditions. The extension of chemical vapor deposition to elevated pressure is also necessary for retaining stoichiometric single phase surface composition for materials that are characterized by large thermal decomposition pressures at optimum processing temperatures.

Dietz, Nikolaus; Woods, Vincent; McCall, Sonya D.; Bachmann, Klaus J.

2003-01-01

275

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

276

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

NASA Technical Reports Server (NTRS)

The goal of this program is to demonstrate that a dichlorosilane-based reductive chemical vapor deposition (CVD) process is capable of producing, at low cost, high quality polycrystalline silicon. Physical form and purity of this material will be consistent with LSA material requirements for use in the manufacture of high efficiency solar cells. Four polysilicon deposition runs were completed in an intermediate size reactor using dichlorosilane fed from 250 pound cylinders. Results from the intermediate size reactor are consistent with those obtained earlier with a small experimental reactor. Modifications of two intermediate size reactors were completed to interface with the dichlorosilane process demonstration unit (PDU).

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

1982-01-01

277

27 CFR 41.38 - Cigarettes.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Cigarettes. 41.38 Section 41.38 Alcohol... IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO... Classification of Large Cigars and Cigarettes § 41.38 Cigarettes. For...

2010-04-01

278

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...IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED... Taxes Tax Rates § 41.34 Cigarette papers. Cigarette papers...

2010-04-01

279

27 CFR 41.35 - Cigarette tubes.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Cigarette tubes. 41.35 Section 41...IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED... Taxes Tax Rates § 41.35 Cigarette tubes. Cigarette tubes...

2010-04-01

280

A low phase noise microwave frequency synthesis for a high-performance cesium vapor cell atomic clock.  

PubMed

We report the development, absolute phase noise, and residual phase noise characterization of a 9.192?GHz microwave frequency synthesis chain devoted to be used as a local oscillator in a high-performance cesium vapor cell atomic clock based on coherent population trapping (CPT). It is based on frequency multiplication of an ultra-low phase noise 100 MHz oven-controlled quartz crystal oscillator using a nonlinear transmission line-based chain. Absolute phase noise performances of the 9.192?GHz output signal are measured to be -42, -100, -117 dB?rad(2)/Hz and -129 dB?rad(2)/Hz at 1 Hz, 100 Hz, 1 kHz, and 10 kHz offset frequencies, respectively. Compared to current results obtained in a state-of-the-art CPT-based frequency standard developed at LNE-SYRTE, this represents an improvement of 8 dB and 10 dB at f = 166 Hz and f = 10 kHz, respectively. With such performances, the expected Dick effect contribution to the atomic clock short term frequency stability is reported at a level of 6.2 × 10(-14) at 1 s integration time, that is a factor 3 higher than the atomic clock shot noise limit. Main limitations are pointed out. PMID:25273756

François, B; Calosso, C E; Danet, J M; Boudot, R

2014-09-01

281

A low phase noise microwave frequency synthesis for a high-performance cesium vapor cell atomic clock  

NASA Astrophysics Data System (ADS)

We report the development, absolute phase noise, and residual phase noise characterization of a 9.192 GHz microwave frequency synthesis chain devoted to be used as a local oscillator in a high-performance cesium vapor cell atomic clock based on coherent population trapping (CPT). It is based on frequency multiplication of an ultra-low phase noise 100 MHz oven-controlled quartz crystal oscillator using a nonlinear transmission line-based chain. Absolute phase noise performances of the 9.192 GHz output signal are measured to be -42, -100, -117 dB rad2/Hz and -129 dB rad2/Hz at 1 Hz, 100 Hz, 1 kHz, and 10 kHz offset frequencies, respectively. Compared to current results obtained in a state-of-the-art CPT-based frequency standard developed at LNE-SYRTE, this represents an improvement of 8 dB and 10 dB at f = 166 Hz and f = 10 kHz, respectively. With such performances, the expected Dick effect contribution to the atomic clock short term frequency stability is reported at a level of 6.2 × 10-14 at 1 s integration time, that is a factor 3 higher than the atomic clock shot noise limit. Main limitations are pointed out.

François, B.; Calosso, C. E.; Danet, J. M.; Boudot, R.

2014-09-01

282

Magnetic property variation with vapor-phase alteration in the Bishop Tuff, and implications for paleointensity studies  

NASA Astrophysics Data System (ADS)

To obtain reliable estimates of the absolute strength of the geomagnetic field, samples must contain fine-grained (single domain) particles of magnetic minerals, which are thermally stable enough to withstand the arduous measurement process. Ash flow tuffs (ignimbrites) usually fit this first requirement, but may also contain coarser grained material. Ignimbrites may have a complicated thermal and/or chemical magnetic remanence and complex magnetic mineralogies due to emplacement and post-emplacement alteration conditions. The origin and nature of their magnetic remanence must be known in order to interpret the paleointensity. We examined ignimbrites from the 0.76 Ma Bishop Tuff, collecting samples from three stratigraphic sections of the Owens' river gorge that complement two previously sampled sections. Four of the Owens' river gorge sites are within the zone of vapor-phase alteration, three of which are in the zone of fumarolic mounds, but not associated with any specific fumaroles. Within each section there is a range in degree of welding, and between sections there were variations in emplacement and post-emplacement conditions. Previous ?18O studies show ?18O varies considerably with depth within the fumarole zone, where values are dramatically depleted due to meteoric-hydrothermal alteration; however, more densely welded material lower in the same sections did not experience alteration because of their lower permeability. We therefore made an evaluation of the effects of vapor-phase alteration on the ignimbrite's magnetization. We observe a significant decrease in magnetic susceptibility in two sections within the fumarole zone with a sharp increase in the densely welded tuff, which corroborates the ?18O evidence. Hysteresis loops also show the effect of the vapor-phase alteration on the magnetic mineralogy. Coincident with the decrease in susceptibility, at least, one section has wasp-waisted hysteresis loops indicating two coercivity fractions. The high-coercivity fraction is thought to be titanohematite resulting from the alteration process. These effects seem to be spatially heterogeneous however; the decrease in susceptibility and distorted hysteresis loops are not observed at all of the sections within the fumarole zone. Previous work suggest that despite its complex alteration the Bishop Tuff gives an internally consistent estimate of the paleofield; modified Thellier-Thellier experiments are underway to investigate this further. Ignimbrites are globally abundant and many are well dated making them possibly valuable sources of much needed absolute paleointensity information.

Avery, M. S.; Gee, J. S.; Bowles, J. A.; Jackson, M. J.

2012-12-01

283

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

284

Structural changes during vapor-phase deposition of polycrystalline-PbI 2 films  

NASA Astrophysics Data System (ADS)

Lead iodide (PbI 2) polycrystalline thin films with [0 0 1] and [1 1 0] orientations have been grown using a physical vapor-deposition method on substrates coated with ITO or gold electrodes. The films orientation as function of the deposition conditions, such as substrate temperature and coating material, was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Four different types of structures of PbI 2 films deposited on ITO were identified and named A, B, C and D, where each structure is stable in its own temperature range. Changes of structure during the growth process due to the temperature range change were demonstrated. Moreover, the dependence of the temperature range and film structure on substrate coating materials was found. The electrical properties and detector response correlation with film structure have been summarized.

Schieber, M.; Zamoshchik, N.; Khakhan, O.; Zuck, A.

2008-06-01

285

DrugFacts: Electronic Cigarettes (e-Cigarettes)  

MedlinePLUS

... and delivers nicotine but with less of the toxic chemicals produced by burning tobacco leaves. Because they ... as if they may be a safer, less toxic alternative to conventional cigarettes. E-Cigarette Use by ...

286

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

287

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

E-print Network

that some youth are initiat- ing use of the addictive drug nicotine with e-cigarettes.1 E-cigarettes are aggressively adver- tised on television, on the radio, on the Internet, and in magazines, and e-cig- arettes, chocolate, bubble gum, and gummy bear). E-cigarette advertising promises to deliver nicotine, the addictive

Derisi, Joseph

288

Dioxins in cigarette smoke  

SciTech Connect

Dioxins in cigarettes, smoke, and ash were determined using gas chromatography/mass spectrometry. The total concentration of polychlorinated dibenzo-p-dioxins (PCDDs) in cigarette smoke was approximately 5.0 micrograms/m3 at the maximum level, whereas various congeners from tetra-octa-chlorodibenzo-p-dioxin (-CDD) were detected. Particullary, the total concentration of hepta-CDD congeners was the highest among these congeners. Mass fragmentograms of various PCDD congeners were similar to those in flue gas samples collected from a municipal waste incinerator. The PCDD congeners that were not present in the cigarettes were found in the smoke samples. The 2,3,7,8-TCDD toxic equivalent value--an index for effects on humans--for total PCDDs in smoke was 1.81 ng/m3 using the toxic factor of the United States Environment Protection Agency. Daily intake of PCDDs by smoking 20 cigarettes was estimated to be approximately 4.3 pg.kg body weight/day. This value was close to that of the ADIs: 1-5 pg.kg body weight/day reported in several countries. A heretofore unrecognized health risk was represented by the presence of PCDDs in cigarette smoke.

Muto, H.; Takizawa, Y.

1989-05-01

289

Performance of a six-port simulated moving-bed pilot plant for vapor-phase adsorption separations  

SciTech Connect

A simulated moving-bed (SMB) pilot plant, characterized by two unique features, the number of ports (6 instead of 24, as in most industrial applications) and the fluid phase (vapor rather than liquid), has been built and operated. Such a plant has proven capable to achieve complete separation for a mixture of m- and p-xylene using isopropylbenzene as desorbent and KY zeolites as adsorbent. The dynamic behavior of the unit has been investigated and compared with model predictions, both in terms of approach to cyclic steady state as well as of responses to typical inputs. The role of the key design parameters on the steady-state separation performance of the unit has been analyzed experimentally, demonstrating the consistency with the predictions of the Equilibrium Theory.

Storti, G. (Univ. Degli Studi Di Padova (Italy)); Mazzotti, M.; Furlan, L.T.; Morbidelli, M.; Carra, S. (Politecnico Di Milano, (Italy))

1992-11-01

290

Growth and orientation of GaN epilayers on NdGaO3 by hydride vapor phase epitaxy  

Microsoft Academic Search

Growth characteristics of GaN on NdGaO3 (011) and (101) substrates by hydride vapor phase epitaxy are investigated. The epitaxial relationship is found to be GaN(0001)\\/NdGaO3 (011) with GaN [10-10]\\/\\/NdGaO3 [100] for NdGaO3 (011) and GaN(11-24)\\/NdGaO3(101) with GaN[11-2-4]\\/\\/NdGaO3 [10-1] for the NdGaO3 (101). When the GaN is directly grown on NdGaO3substrates around 1000°C, no deposits of GaN are obtained due to

A. Wakahara; T. Nishida; K. Kawano; A. Yoshida; Y. Seki; O. Oda

1998-01-01

291

Thermodynamics on hydride vapor phase epitaxy of AlN using AlCl3 and NH3  

NASA Astrophysics Data System (ADS)

A thermodynamic analysis on hydride vapor phase epitaxy (HVPE) of AlN using AlCl3 and NH3 was performed. Regardless of the carrier gas used, partial pressures of Al-containing gaseous species [AlCl3, AlCl2, AlCl and (AlCl3)2] in equilibrium with AlN are significantly low in the temperature range of 500-1500 °C when the input V/III ratio is above 1. This means that the driving force for AlN growth (?PAl) becomes almost equal to the input partial pressure of AlCl3, which is quite different from HVPE of GaN. The good agreement between the calculated and experimental growth rates shows that HVPE of AlN is thermodynamically controlled.

Kumagai, Y.; Takemoto, K.; Kikuchi, J.; Hasegawa, T.; Murakami, H.; Koukitu, A.

292

Successful natural stress-induced separation of hydride vapor phase epitaxy-grown GaN layers on sapphire substrates  

NASA Astrophysics Data System (ADS)

This paper presents the behavior of GaN layers on sapphire substrates in successful natural stress-induced separation. It was revealed that a separation plane was formed in the middle of a hydride vapor phase epitaxy-grown GaN layer under specific conditions. One possible reason is that the proper temperature gradient produces a driving force for the separation during the cooling process. No dislocation and no cracks generated through the cooling process. As a result, a single piece of 2? GaN wafer with a crack-free mirror surface was obtained. The full width at half maximum of X-ray rocking curve and dislocation density of the freestanding GaN wafer were less than 65 arcsec and 8×106 cm-2, respectively, indicating the high crystalline quality.

Yamane, K.; Ueno, M.; Furuya, H.; Okada, N.; Tadatomo, K.

2012-11-01

293

Hydride Vapor-Phase Epitaxy of c-Plane AlGaN Layers on Patterned Sapphire Substrates  

NASA Astrophysics Data System (ADS)

Growth of Al x Ga1- x N layers by hydride vapor-phase epitaxy on patterned sapphire substrates is investigated. The pattern consists of honeycombs which by their orientation and size promote the formation of coalesced c-plane-oriented Al x Ga1- x N layers with reduced crack density. The orientation of parasitic crystallites in the honeycomb openings is investigated using scanning electron microscopy and electron back-scatter diffraction. Crystallites with their [ .0] and [52.3] directions parallel to the vertical growth direction of the Al0.3Ga0.7N layer are observed and successfully overgrown by a 20- ?m-thick fully coalesced c-plane-oriented layer.

Richter, E.; Fleischmann, S.; Goran, D.; Hagedorn, S.; John, W.; Mogilatenko, A.; Prasai, D.; Zeimer, U.; Weyers, M.; Tränkle, G.

2014-04-01

294

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

295

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

296

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

297

Quantifying The Uncertainties Associated With Analytical-Model Approximations In Vapor-Phase Pump-Test Analysis  

NASA Astrophysics Data System (ADS)

Soil vapor extraction (SVE) is a proven method for remediation of nonaqueous phase liquids (NAPLs) in the vadose zone. Knowledge of the average gas-phase permeability and water content in the clean-up zone is important for design and operation of SVE systems. SVE pump tests are frequently used to assess these parameters. SVE pump-test analyses are usually analyzed using simplified analytical models for gas flow in porous media. Typically, model-input values for gas-phase permeability and water content are varied until the global errors between the calculated and measured gas pressures are minimized. These optimized values are assumed to be equal to the actual gas permeability and water content. For this research, hypothetical data sets are generated for idealized SVE operations in a radially symmetric aquifer using a numerical multiphase-flow model. Using a mathematical-inversion technique, we evaluate the uncertainties associated with the typical assumptions inherent in analytical models for nearly homogeneous confined and "leaky" vadose zones. The influences of several variables and processes that are typically not accounted for in the analytical models are assessed. These include variable water content, anisotropy, nonisothermal conditions, variable mass flow rate, gas compressibility, and linearization of the PDE used for the analytical solutions.

McCray, J. E.; Neville, C. J.

2001-05-01

298

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

299

Metalorganic Vapor Phase Epitaxy Growth of m-Plane GaN Using LiAlO2 Substrates  

NASA Astrophysics Data System (ADS)

The crystalline, surface, and optical properties of the m-plane GaN layer grown on the LiAlO2 (LAO) substrate by metalorganic vapor phase epitaxy (MOVPE) were demonstrated. The low temperature growth of the GaN buffer layer, performed in the nitrogen ambient, could lead to the smooth surface morphology. Because of the small lattice mismatch between GaN and the LAO substrate, the low-density line-shaped defects, possibly originated from stacking faults, were observed. In addition, high phase purity of the m-plane GaN epilayer was shown in the high resolution X-ray diffraction (HRXRD) spectrum. The different behavior was found for donor-bound exciton (D0X) and defect-related transitions, characterized by the temperature-dependent photoluminescence (PL) measurement. These results suggest that the nitridation process and low temperature growth of the GaN buffer layer under nitrogen ambient could be suitable for realizing smooth and high phase purity m-plane GaN on LAO substrates.

Cheng, An-Ting; Su, Yan-Kuin; Lai, Wei-Chih; Chen, Ying-Zhi

2008-04-01

300

MW Spectroscopy Coupled with Ultrafast UV Laser Vaporization: Succinic Acid in the Gas Phase  

NASA Astrophysics Data System (ADS)

Recent lab and field measurements have indicated critical roles of organic acids in enhancing new atmospheric aerosol formation. In order to understand the nucleation process, here we report an experimental and theoretical investigation of chemical structure of succinic acid. We have used the technique of Fourier Transform Microwave Spectroscopy (FTMW). Succinic acid was vaporized by UV ultrafast laser ablation to suppress thermal decomposition processes^a and seeded into an expanding stream of Ne forming a supersonic jet. The rotational spectrum detected the presence of a single most stable conformation in the cm- mm- wave regions for which accurate rotational and centrifugal distortion parameters have been determined. The study was extended to all monosubstituted isotopic species (^{13}C, ^{18}O, D(O)), which were positively identified, leading to an accurate determination of the effective and substitution structures of the molecule. The experimental study was supplemented by ab initio (MP2) and DFT (M06-2X and B3LYP) calculations. ^{a} E. J. Cocinero, A. Lesarri, P. écija, F. J. Basterretxea, J. U. Grabow, J. A. Fernández and F. Castaño, Angew. Chem. Int. Ed., 51, 3119-3124, 2012.

Mendez, Estibaliz; Ecija, Patricia; Cocinero, Emilio J.; Castano, Fernando; Basterretxea, Francisco J.; Godfrey, Peter D.; McNaughton, Don; Jahn, Michaela K.; Nair, K. P. Rajappan; Grabow, Jens-Uwe

2013-06-01

301

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

302

Proceedings of the Symposium on Fundamental Gas-Phase and Surface Chemistry of Vapor-Phase Materials Synthesis,  

E-print Network

to remove silanols and water from oxide thin films is not viable for TEOS/ozone applications as it negates-Phase Materials Synthesis, PV98-28, p. 153,The Electrochemical Society, 1998. IN SITU STUDIES OF TEOS/OZONE CVD are described that show this layer to have a thickness of ca. 2-mm. Fiber optic approaches are described

Taylor, James H.

303

Vapor-phase metalation by atomic layer deposition in a metal-organic framework.  

PubMed

Metal-organic frameworks (MOFs) have received attention for a myriad of potential applications including catalysis, gas storage, and gas separation. Coordinatively unsaturated metal ions often enable key functional behavior of these materials. Most commonly, MOFs have been metalated from the condensed phase (i.e., from solution). Here we introduce a new synthetic strategy capable of metallating MOFs from the gas phase: atomic layer deposition (ALD). Key to enabling metalation by ALD In MOFs (AIM) was the synthesis of NU-1000, a new, thermally stable, Zr-based MOF with spatially oriented -OH groups and large 1D mesopores and apertures. PMID:23829224

Mondloch, Joseph E; Bury, Wojciech; Fairen-Jimenez, David; Kwon, Stephanie; DeMarco, Erica J; Weston, Mitchell H; Sarjeant, Amy A; Nguyen, SonBinh T; Stair, Peter C; Snurr, Randall Q; Farha, Omar K; Hupp, Joseph T

2013-07-17

304

Transfer of amplitude and phase modulation to a different wavelength using coherently prepared sodium vapor  

E-print Network

, pre- serving the spectral power distribution in the process 38 . But scattering stimulated information content of an optical field from one spectral band to another with good efficiency, high fidelity of light 1,28 . EIT and related ideas have led to efficient infrared up conversion 29,30 , efficient phase

Stroud Jr., Carlos R.

305

Prediction of methanol loss in vapor phase during gas hydrate inhibition using Arrhenius-type functions  

Microsoft Academic Search

Gas hydrate formation in natural gas and NGL systems can block pipelines, equipment, and instruments, restricting or interrupting flow leading to safety hazards to production\\/transportation systems and to substantial economic risks. The amount of hydrate inhibitor to be injected not only must be sufficient to prevent freezing of the inhibitor water phase, but also must be sufficient to provide for

Alireza Bahadori; Hari B. Vuthaluru

2010-01-01

306

Bulk Property Modification of Fiber Forming Polymers using Vapor Phase Techniques  

NASA Astrophysics Data System (ADS)

Atomic layer deposition provides the opportunity to introduce nanoscale inorganic coatings to organic polymers creating coatings with varied compositions of finish and distinctive interfaces. Prior research has shown that ALD materials nucleation on polymers varies in composition and structure based on how the precursor interacts with the polymer chemistry and the process conditions. To study this in more detail, in-situ quartz crystal microgravimetry is employed to understand the infiltration and saturation behavior of trimethyl aluminum in polymer thin films. Emphasis is placed on understanding reactive vapor diffusion into polymers as the exposure temperature is varied. Potential growth mechanisms based on the temperature dependent observations in this work are proposed which leads to the understanding of hybrid organic-inorganic formation in polymers. Furthermore, polymers which have subtle variations in microstructure are explored to elucidate the nucleation behavior of inorganic coatings on polymers in more detail. Specifically, in-situ quartz crystal microgravimetry is employed to understand the nucleation behavior of alumina ALD in a series of poly-n-methacrylate and polyester thin films. The work indicates the effect that a subtle change in polymer microstructure has on the properties of the polymer film and the resultant absorption/desorption characteristics during TMA/water exposures. The effect of % crystallinity on the infiltration mechanism is also investigated in polymer films with varied crystallinities. Finally, the effect of the hybrid modification on the mechanical behavior of fibrous materials is also explored. In particular this dissertation highlights the process-property relationships between modified and unmodified fibers infiltrated with TMA. The results indicate that the peak load and elongation of the fibers increase with exposure to TMA. Therefore, this work has important implications on high impact applications as well as the introduction of inorganic material properties to flexible polymer systems.

Padbury, Richard Paul

307

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

308

Weathering mechanisms and their effects on the landsliding of ignimbrite subject to vapor-phase crystallization in the Shirakawa pyroclastic flow, northern Japan  

Microsoft Academic Search

Ignimbrite, which is consolidated by vapor-phase crystallization, is weathered in humid regions to form a special type of weathering profile that consists of a hydrated zone, an exfoliated zone, and a disintegrated zone from the depth to the ground surface, with each zone having a basal front. The ignimbrite is hydrated first and loses a significant amount of phosphorous at

M Chigira; M Nakamoto; E Nakata

2002-01-01

309

This paper presents the model for pattern formation in the course of thermodynamically stable and unstable crystal growth from vapor phase, which is in uenced by rapid spatio-  

E-print Network

stable and unstable crystal growth from vapor phase, which is in uenced by rapid spatio- temporal of spatiotemporal chaos as the growth rate increases. INTRODUCTION Recent experimental work done in the group crystal surfaces structures are formed by the combined action of the deposition, faceting instability

Khenner, Mikhail

310

The formation of PdCx over Pd-based catalysts in vapor-phase vinyl acetate synthesis: does a PdAu alloy catalyst resist carbide formation?  

E-print Network

The formation of PdCx over Pd-based catalysts in vapor-phase vinyl acetate synthesis: does a Pd­Au alloy catalyst resist carbide formation? Y.-F. Han, D. Kumar, C. Sivadinarayana, A. Clearfield, and D acetate (VA) was investigated over Pd/SiO2 catalysts with two different Pd particle sizes, as well as over

Goodman, Wayne

311

Photoluminescence from intermediate phase silicon structure and nanocrystalline silicon in plasma enhanced chemical vapor deposition grown Si\\/SiO2 multilayers  

Microsoft Academic Search

Amorphous Si\\/SiO2 multilayers (MLs) on silicon wafers were fabricated in a plasma enhanced chemical vapor deposition system via cycles of silicon deposition and plasma oxidation. The structural and optical properties of the MLs were characterized using transmission electron microscopy, Raman scattering and room temperature photoluminescence (PL) measurements. Intermediate phase silicon structure (IPSS), which is intermediate in order between the continuous

P. G. Han; Z. Y. Ma; Z. B. Wang; X. Zhang

2008-01-01

312

A facile vapor-phase hydrothermal method for direct growth of titanate nanotubes on a titanium substrate via a distinctive nanosheet roll-up mechanism.  

PubMed

We present a facile vapor-phase hydrothermal approach for direct growth of vertically aligned titanate nanotubes on a titanium foil substrate. The resultant nanotubes display external diameters of 50-80 nm and walls with an average thickness of 10 nm that consist of more than 10 titanate layers. This is in strong contrast to the titanate nanotubes obtained from alkaline liquid-phase hydrothermal methods, which are generally smaller than 12 nm in external diameter and have walls consisting of less than five titanate layers. Importantly, the investigation confirmed that under vapor-phase hydrothermal conditions, the nanotubes were formed via a distinctive nanosheet roll-up mechanism that differs remarkably from those of conventional liquid-phase hydrothermal processes. For the first time, a coaxial circular cylinder crystal structure of the resultant nanotubes was confirmed. PMID:22035232

Liu, Porun; Zhang, Haimin; Liu, Hongwei; Wang, Yun; Yao, Xiangdong; Zhu, Guangshan; Zhang, Shanqing; Zhao, Huijun

2011-11-30

313

Metalorganic vapor phase epitaxy of wide-gap II VI semiconductors for optoelectronic applications: current status and future trends  

NASA Astrophysics Data System (ADS)

The current status and future trends to overcome the major problems of wide-gap II-VI compounds grown by metalorganic vapor phase epitaxy (MOVPE) which are p-type doping and the understanding of interface properties of {ZnSSe}/{ZnSe-based} heterostructures will be discussed. Since a low growth temperature is required to reduce defects and impurities and to increase the sticking coefficient of dopant atoms, a matched precursor combination of zinc and selenium compounds or an additional growth assistance (e.g. plasma stimulation) must be employed. The optical and electrical properties of ZnSe doped with nitrogen will be discussed. Emphasis will be put on the fact that most of the MOVPE grown ZnSe:N layers remain highly resistive or that they show only low free hole concentrations. Occurring compensation mechanisms such as parasitic compensating donors associated with nitrogen or compensating nitrogen-hydrogen complexes may be the reason. The ability of MOVPE to handle high vapor pressure elements such as sulphur favours this technology for the growth of sophisticated quantum wells and superlattices to achieve electrical and optical confinement in laser structures and to push the emission wavelength further into the blue. Scanning transmission electron microscope, photoluminescence (PL) and X-ray measurements were used for the analysis of the interface properties. Growth optimization of {ZnSSe}/{ZnSe} interfaces results in monolayer fluctuations at the interfaces. High excitation PL experiments show that room temperature stimulated emission is possible with this kind of structures. To realize high bit rate data transmission in the blue spectral range at 2.7 eV the physical properties of optoelectronic modulators based on {ZnSSe}/{ZnSe} superlattices were examined.

Heuken, Michael

1995-01-01

314

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

315

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

316

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

317

[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

318

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

319

Effect of Mo Dispersion Size and Water Vapor on Oxidation of Two-Phase Directionally Solidified NiAl-9Mo In-Situ Composites  

SciTech Connect

Oxidation of two-phase NiAl-9Mo eutectics with 3 different growth rates/2nd phase Mo dispersion sizes were investigated at 900 C in air and air with 10% water vapor. Good oxidation resistance via alumina formation was observed in dry air, with Mo volatilization loss minimized by fine submicron Mo dispersions. However, extensive Mo volatilization and in-place internal oxidation of prior Mo phase regions was observed in wet air oxidation. Ramifications of this phenomenon for the development of multi-phase high-temperature alloys are discussed

Brady, Michael P [ORNL] [ORNL; Bei, Hongbin [ORNL] [ORNL; Meisner, Roberta Ann [ORNL] [ORNL; Lance, Michael J [ORNL] [ORNL; Tortorelli, Peter F [ORNL] [ORNL

2014-01-01

320

Water Vapor: Distribution and Trends  

Microsoft Academic Search

Water in the gaseous phase, water vapor, is the most significant atmospheric trace constituent vis-` a-vis climate, weather, hydro- logy, and atmospheric chemistry. Water vapor is the most abundant atmospheric greenhouse gas, and without it the planet's sur- face temperature would be well below freezing. Phase changes involving water vapor - the condensation and evaporation pro- cesses - involve exchanges

Dian J Seidel

2002-01-01

321

A new look at radicals in cigarette smoke.  

PubMed

Radicals in cigarette smoke have been proposed to contribute to the harm caused by cigarette smoking. For the first time, using HPLC and high-resolution mass spectrometry analysis of stable radical adducts, we have identified specific radical species in cigarette smoke: 7 acyl and 11 alkylaminocarbonyl radicals. Their combined abundance measured in fresh whole smoke from a single 2R4F cigarette is approximately 225 nmol (1.4 x 10(17) radicals). The fiberglass Cambridge filter pad conventionally employed to separate the gas phase from mainstream smoke was found to reduce the apparent yield of these radicals, introducing artifacts of measurement. The long-accepted steady-state mechanism for the formation of carbon-centered radicals in cigarette smoke involving NO2 chemistry cannot account for these newly identified radicals, and it does not in general appear to be a major source of carbon-centered radicals in fresh mainstream cigarette smoke. Consequently, we suggest that the precise nature of radicals in cigarette smoke warrants reexamination. PMID:17530742

Bartalis, Judit; Chan, W Geoffrey; Wooten, Jan B

2007-07-01

322

Cigarette smoke inhibition of ion transport in canine tracheal epithelium  

SciTech Connect

To determine the effect of cigarette smoke on airway epithelial ion transport, the electrical properties and transepithelial Na and Cl fluxes were measured in canine tracheal epithelium. In vivo, the inhalation of the smoke from one cigarette acutely and reversibly decreased the electrical potential difference across the tracheal epithelium. In vitro, exposure of the mucosal surface of the epithelium to cigarette smoke decreased the short circuit current and transepithelial resistance. The decrease in short circuit current was due to an inhibition of the rate of Cl secretion with minimal effect on the rate of Na absorption. The effect of cigarette smoke was reversible, was not observed upon exposure of the submucosal surface to smoke, and was most pronounced when secretion was stimulated. The particulate phase of smoke was largely responsible for the inhibitory effect, since filtering the smoke minimized the effect. The effect of cigarette smoke was not prevented by addition of antioxidants to the bathing solutions, suggesting that the inhibition of Cl secretion cannot be entirely attributed to an oxidant mechanism. These results indicate that cigarette smoke acutely inhibits active ion transport by tracheal epithelium, both in vivo and in vitro. This effect may explain, in part, both the abnormal mucociliary clearance and the airway disease observed in cigarette smokers.

Welsh, M.J.

1983-06-01

323

Recombinogenic activity of fresh cigarette smoke in Saccharomyces cerevisiae.  

PubMed

A procedure for determining the effect of fresh cigarette smoke on gene conversion in yeast. Saccharomyces cerevisiae D7, is described. Cigarette smoke, generated by a 2-sec, 40-ml puff, once per minute, was puffed into an open-end tube. The smoke was drawn through an exposure vessel containing a continuously stirred, stationary-phase yeast cell suspension, 1-58 sec after generation. Frequency of gene conversion was estimated in samples taken at intervals after the start of exposure. Under these conditions, a five-fold increase in mitotic gene conversion in yeast strain D7 was obtained from exposure to 20 puffs of fresh whole smoke from University of Kentucky Reference Cigarettes (2R1), to 75 puffs from the gas phase of these cigarettes, and to 45 puffs from an acetate filter version (2R1F). Selective removal of genetically active components by acetate filters is suggested since the reduction in recombinogenic activity (55%) is greater than the reduction in total particulate matter yield (25%) of the cigarette. The results indicate that 1) the procedure provides a practical bioassay for determining the effects of fresh smoke on gene conversion in yeast, without external metabolic activation; 2) the gas phase of smoke has recombinogenic activity; and 3) standard acetate filters may selectively remove genetically active components of cigarette smoke. PMID:6762250

Gairola, C C; Griffith, R B

1981-01-01

324

Surface-initiated Ring-opening Metathesis Polymerization in the Vapor Phase: An Efficient Method for Grafting Cyclic Olefins of Low Strain Energies  

PubMed Central

Surface grafting of cyclic olefins with low strain energies, including cyclopentene (CP), 1,4-cyclohexadiene (CHD), cycloheptene (CHP), cis-cyclooctene (CO), cis,cis-1,5-cyclooctadiene (COD), 1,3,5,7-cyclooctatetraene (COT), cyclododecene (CD), and trans,trans,cis-1,5,9-cyclododecatriene (CDT), were explored using ring-opening metathesis polymerization in the vapor phase. These monomers do not polymerize when SiROMP is carried out in solution due to pronounced chain transfer on surfaces where chains are in close proximities. In the vapor phase, however, chain transfer is suppressed at the solid-vapor interfaces, which permits the polymerization of most of these monomers. A minimal required strain energy of 2.2 kcal/mol was determined in this study, which is significantly lower than the estimated 13.3 kcal/mol for SiROMP carried out in solution, indicating that the enhancement in monomer polymerizability is significant using the vapor phase approach. A series of polyalkenamers with controlled fraction of unsaturation from 8% to 50% along the polymer backbone were grafted to solid substrates. It was observed that the logarithm of largest grafted layer thickness obtained before the removal of chain transfer products – which correlates with the extent of polymerization – scales with monomer strain energy. This confirms that the release of ring strain is the thermodynamic driving force for SiROMP. It was also found that although chain transfer is suppressed in the vapor phase, it is important in monomer/polymer systems where the fraction of unsaturated bonds is high. In these cases, grafted polymer thickness is dominated by chain transfer, rather than by monomer strain energy. A quantitative relationship is established for estimating graft thickness of a particular monomer using its strain energy and fraction of unsaturated bonds in the monomer. PMID:21469729

Lerum, Maria Felisa Z.; Chen, Wei

2011-01-01

325

Electronic cigarettes: human health effects  

PubMed Central

Objective With the rapid increase in use of electronic nicotine delivery systems (ENDS), such as electronic cigarettes (e-cigarettes), users and non-users are exposed to the aerosol and product constituents. This is a review of published data on the human health effects of exposure to e-cigarettes and their components. Methods Literature searches were conducted through September 2013 using multiple electronic databases. Results Forty-four articles are included in this analysis. E-cigarette aerosols may contain propylene glycol, glycerol, flavourings, other chemicals and, usually, nicotine. Aerosolised propylene glycol and glycerol produce mouth and throat irritation and dry cough. No data on the effects of flavouring inhalation were identified. Data on short-term health effects are limited and there are no adequate data on long-term effects. Aerosol exposure may be associated with respiratory function impairment, and serum cotinine levels are similar to those in traditional cigarette smokers. The high nicotine concentrations of some products increase exposure risks for non-users, particularly children. The dangers of secondhand and thirdhand aerosol exposure have not been thoroughly evaluated. Conclusions Scientific evidence regarding the human health effects of e-cigarettes is limited. While e-cigarette aerosol may contain fewer toxicants than cigarette smoke, studies evaluating whether e-cigarettes are less harmful than cigarettes are inconclusive. Some evidence suggests that e-cigarette use may facilitate smoking cessation, but definitive data are lacking. No e-cigarette has been approved by FDA as a cessation aid. Environmental concerns and issues regarding non-user exposure exist. The health impact of e-cigarettes, for users and the public, cannot be determined with currently available data. PMID:24732161

Callahan-Lyon, Priscilla

2014-01-01

326

Graphical Interface for the Study of Gas-Phase Reaction Kinetics: Cyclopentene Vapor Pyrolysis  

NASA Astrophysics Data System (ADS)

The undergraduate laboratory experiment on the pyrolysis of gaseous cyclopentene has been modernized to improve safety, speed, and precision and to better reflect the current practice of physical chemistry. It now utilizes virtual instrument techniques to create a graphical computer interface for the collection and display of experimental data. An electronic pressure gauge has replaced the mercury manometer formerly needed in proximity to the 500 °C pyrolysis oven. Students have much better real-time information available to them and no longer require multiple lab periods to get rate constants and acceptable Arrhenius parameters. The time saved on manual data collection is used to give the students a tour of the computer interfacing hardware and software and a hands-on introduction to gas-phase reagent preparation using a research-grade high-vacuum system. This includes loading the sample, degassing it by the freeze-pump-thaw technique, handling liquid nitrogen and working through the logic necessary for each reconfiguration of the diffusion pump section and the submanifolds.

Marcotte, Ronald E.; Wilson, Lenore D.

2001-06-01

327

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

NASA Astrophysics Data System (ADS)

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. Fer?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.

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

2013-02-01

328

Mechanism of arsenic incorporation and electrical properties in CdTe layers grown by metalorganic vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

The As doping mechanism in (100) CdTe layers grown on (100) GaAs by atmospheric-pressure metalorganic vapor phase epitaxy was studied. Triethylarsine (TEAs) was used as a dopant source. The source materials used were dimethylcadmium (DMCd) and diethyltelluride (DETe). The As incorporation was enhanced by decreasing the DETe flow rate under a fixed DMCd flow condition, and by lowering the growth temperature. Assuming 100% activation of As, the As incorporation efficiency was estimated to be about 0.1%. The As incorporation was dominated by the sticking rate of the As species onto the Cd species. The hole concentration was controlled from 2×1015 to 3×1016 cm-3 in proportion to the TEAs flow rate below 1×10-7 mol/min. Those doped layers showed hole mobilities as high as 75 cm2/V s. Low-temperature photoluminescence (PL) studies revealed that a neutral-acceptor bound-exciton at 1.5901 eV is due to a substitutional As acceptor on the Te site. The As ionization energy was about 90 meV from the PL and electrical measurements.

Ekawa, Mitsuru; Yasuda, Kazuhito; Ferid, Touati; Saji, Manabu; Tanaka, Akikazu

1992-03-01

329

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 Li2S offers the possibility to overcome these challenges, but no synthetic technique exists for fine-tailoring Li2S at the nanoscale. Herein we report a vapor-phase atomic layer deposition (ALD) method for the atomic-scale-controllable synthesis of Li2S. Besides a comprehensive investigation of the ALD Li2S growth mechanism, we further describe the high performance of the resulting amorphous Li2S 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 Li2S 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

330

Influence of source gas supply sequence on hydride vapor phase epitaxy of AlN on (0001) sapphire substrates  

NASA Astrophysics Data System (ADS)

AlN layers were grown on (0001) sapphire substrates by hydride vapor phase epitaxy (HVPE) at 1100 °C with a source gas supply sequence of (1) NH3 preflow or (2) AlCl3 preflow. An Al-polarity AlN layer without inclusion of a N-polarity region was grown when AlCl3 was preflown to the sapphire surface prior to AlN growth, while N- and Al-polarity regions were both present in the same AlN layer when NH3 was preflown, since growth was performed on a nitrided sapphire surface. Compared with the AlN layers grown with NH3 preflow, the Al-polarity AlN layers grown with AlCl3 preflow had improved crystalline structural quality, a low concentration of oxygen impurity, and a photoabsorption edge energy of 6.08 eV, which is close to an ideal value. Therefore, the source gas supply sequence has a significant influence on the growth of AlN layers on (0001) sapphire substrates. Thus, preflow of AlCl3 gas to a sapphire surface prior to AlN growth is a key process for high crystalline quality AlN layer growth with uniform Al-polarity on (0001) sapphire substrates by HVPE.

Togashi, Rie; Nagashima, Toru; Harada, Manabu; Murakami, Hisashi; Kumagai, Yoshinao; Yanagi, Hiroyuki; Koukitu, Akinori

2012-12-01

331

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

332

Remediation of nonaqueous phase liquid polluted sites using surfactant-enhanced air sparging and soil vapor extraction.  

PubMed

A two-dimensional laboratory sand tank was installed to study the remediation efficiency of surfactant-enhanced air sparging (-SEAS) coupled with soil vapor extraction (SVE) in nonaqueous phase liquid (NAPL) polluted sites. During initial stages of remediation, it was more reasonable to use conventional air sparging coupled with SVE. When most free NAPLs were removed and contaminant removal rate was maintained at a relatively low level, surfactant was added to the groundwater. During enhanced remediation, lower interfacial tension caused residual NAPLs in the porous media to slightly migrate, making the downstream contaminant concentration somewhat higher. The polluted area, however, was not more enlarged than before. The decrease in surface tension resulted in increased air saturation in the groundwater and the extent of the air influence zone. After 310 hours, 78.7% of the initial chlorobenzene mass had volatilized, 3.3% had migrated out of the sand profile, 17.5% was in the vadose zone, and 0.5% remained in the groundwater, thus revealing that SEAS/SVE can effectively improve the remediation of NAPL polluted sites. PMID:23472329

Qin, Chuan-Yu; Zhao, Yong-Sheng; Su, Yan; Zheng, Wei

2013-02-01

333

Photoemission spectroscopy and atomic force microscopy investigation of vapor-phase codeposited silver/poly(3-hexylthiophene) composites.  

PubMed

Nanocomposite matrices of silver/poly(3-hexylthiophene) (P3HT) were prepared in ultrahigh vacuum through vapor-phase codeposition. Change in microstructure, chemical nature, and electronic properties with increasing filler (Ag) content were investigated using in situ XPS and UPS, and ambient AFM. At least two chemical binding states occur between Ag nanoparticles and sulfur in P3HT at the immediate contact layer, but no evidence of interaction between Ag and carbon (in P3HT) was found. AFM images reveal a change in Ag nanoparticles size with concentration which modifies the microstructure and the average roughness of the surface. Under codeposition, P3HT largely retains its conjugated structures, which is evidenced by the similar XPS and UPS spectra to those of P3HT films deposited on other substrates. We demonstrate here that the magnitude of the barrier height for hole injection (epsilon(v)(F)) and the position of the highest occupied band edge (HOB) with respect to the Fermi level of Ag may be controlled and changed by adjusting the metal (Ag) content in the composite. Furthermore, UPS reveals distinct features related to the C 2p (sigma states) in the 5-12 eV regions, indicating the presence of ordered P3HT, which is different from solution processed films. PMID:20356149

Scudiero, L; Wei, Haoyan; Eilers, Hergen

2009-12-01

334

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

335

Metalorganic vapor phase epitaxial growth of red and infrared vertical-cavity surface-emitting laser diodes  

NASA Astrophysics Data System (ADS)

Metalorganic vapor phase epitaxy (MOVPE) is used for the growth of vertical-cavity surface-emitting laser (VCSEL) diodes. MOVPE exhibits a number of important advantages over the more commonly-used molecular-beam epitaxial (MBE) techniques, including ease of continuous compositional grading and carbon doping for low-resistance p-type distributed Bragg reflectors (DBRs), higher growth rates for rapid throughput and greater versatility in choice of materials and dopants. Planar gain-guided red VCSELs based on AlGaInP/AlGaAs heterostructures lase continuous-wave at room temperature, with voltage thresholds between 2.5 and 3 V and maximum power outputs of over 0.3 mW. Top-emitting infra-red (IR) VCSELs exhibit the highest power-conversion (wall-plug) efficiencies (21%), lowest threshold voltage (1.47 V), and highest single mode power (4.4 mW from an 8 ?m device) yet reported. These results establish MOVPE as a preferred growth technique for this important new family of photonic devices.

Schneider, R. P.; Lott, J. A.; Lear, K. L.; Choquette, K. D.; Crawford, M. H.; Kilcoyne, S. P.; Figiel, J. J.

1994-12-01

336

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

337

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

338

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

339

Patterning and overgrowth of nanostructure quantum well wire arrays by LP-MOVPE (low pressure Metalorganic Vapor Phase Epitaxy)  

SciTech Connect

Nanometer scale GaAs Quantum Well Wire (QWW) arrays with lateral dimensions in the range of 10--70 nm and a period of 200 nm have been fabricated in the GaAs/AlGaAs system using x-ray nanolithography patterning and overgrowth by a low pressure Metalorganic Vapor Phase Epitaxy (LP-MOVPE) technique. The QWW structures were either fabricated by post-growth patterning of a thin GaAs film on a AlGaAs-coated substrate followed by AlGaAs deposition, or by continuous in-situ deposition of a GaAs/AlGaAs QWW structure on a prepatterned GaAs substrate. Although cross-sectional transmission electron microscopy showed no structural defects in either QWW fabrication process, photoluminescence (PL) was only observed in the in-situ-deposited structures. Strong polarization dependence of the PL peak with respect to wire orientation has been confirmed and evidence of lateral confinement was observed. 17 refs., 4 figs.

Karam, N.H.; Mastrovito, A.; Haven, V. (Spire Corp., Bedford, MA (USA)); Ismail, K. (International Business Machines Corp., Yorktown Heights, NY (USA). Thomas J. Watson Research Center); Pennycook, S. (Oak Ridge National Lab., TN (USA)); Smith, H.I. (Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Electrical Engineering and Computer Science)

1990-06-01

340

Controlled Vapor Phase Growth of Single Crystalline, Two-Dimensional GaSe Crystals with High Photoresponse  

SciTech Connect

Abstract Compared with their bulk counterparts, atomically thin two-dimensional (2D) crystals exhibit new physical properties, and have the potential to enable next-generation electronic and optoelectronic devices. However, controlled synthesis of large uniform monolayer and multi-layer 2D crystals is still challenging. Here, we report the controlled synthesis of 2D GaSe crystals on SiO2/Si substrates using a vapor phase deposition method. For the first time, uniform, large (up to ~60 m in lateral size), single-crystalline, triangular monolayer GaSe crystals were obtained and their atomic resolution structure were characterized. The size, density, shape, thickness, and uniformity of the 2D GaSe crystals were shown to be controllable by growth duration, growth region, growth temperature, and argon carrier gas flow rate. The theoretical modeling of the electronic structure and Raman spectroscopy demonstrate a direct-to-indirect bandgap transition and progressive confinement-induced bandgap shifts for 2D GaSe crystals. The 2D GaSe crystals show p-type semiconductor characteristics and high photoresponsivity (~1.7 A/W under white light illumination) comparable to exfoliated GaSe nanosheets. These 2D GaSe crystals are potentially useful for next-generation electronic and optoelectronic devices such as photodetectors and field-effect transistors.

Li, Xufan [ORNL; Lin, Ming-Wei [ORNL; Zhang, Huidong [University of Tennessee, Knoxville (UTK); Puretzky, Alexander A [ORNL; Idrobo Tapia, Juan C [ORNL; Ma, Cheng [ORNL; Chi, Miaofang [ORNL; Yoon, Mina [ORNL; Rouleau, Christopher M [ORNL; Kravchenko, Ivan I [ORNL; Geohegan, David B [ORNL; Xiao, Kai [ORNL

2014-01-01

341

International cigarette labelling practices  

Microsoft Academic Search

DESIGNCross-sectional study.PARTICIPANTSMembers 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 MEASURESPresence 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.RESULTSForty-five

Macksood Aftab; Deborah Kolben; Peter Lurie

1999-01-01

342

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

343

She smoked a cigarette : elle fumait une cigarette ou elle fuma une cigarette Prtrit simple et construction de la tlicit  

E-print Network

1 1 She smoked a cigarette : elle fumait une cigarette ou elle fuma une cigarette ? Prétérit simple a cigarette and held it in her bright red lips. When she took it out the cigarette had a pattern of fine red traduction de la phrase en italique par S. Mayoux, dans l'édition française2 : Elle fumait une cigarette qu

Paris-Sud XI, Université de

344

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... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes §...

2010-04-01

345

27 CFR 40.352 - Cigarette tubes.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Cigarette tubes. 40.352 Section 40.352... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes §...

2010-04-01

346

27 CFR 41.35 - Cigarette tubes.  

Code of Federal Regulations, 2011 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.35 Cigarette tubes. Cigarette tubes...

2011-04-01

347

27 CFR 41.35 - Cigarette tubes.  

Code of Federal Regulations, 2012 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.35 Cigarette tubes. Cigarette tubes...

2012-04-01

348

27 CFR 40.352 - Cigarette tubes.  

Code of Federal Regulations, 2012 CFR

...AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.352 Cigarette...

2012-04-01

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27 CFR 41.34 - Cigarette papers.  

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.34 Cigarette papers. Cigarette...

2014-04-01

350

27 CFR 41.34 - Cigarette papers.  

Code of Federal Regulations, 2012 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.34 Cigarette papers. Cigarette...

2012-04-01

351

27 CFR 40.351 - Cigarette papers.  

Code of Federal Regulations, 2011 CFR

...AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.351 Cigarette papers....

2011-04-01

352

27 CFR 40.352 - Cigarette tubes.  

Code of Federal Regulations, 2013 CFR

...AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.352 Cigarette...

2013-04-01

353

27 CFR 41.35 - Cigarette tubes.  

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.35 Cigarette tubes. Cigarette tubes...

2014-04-01

354

27 CFR 41.35 - Cigarette tubes.  

Code of Federal Regulations, 2013 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.35 Cigarette tubes. Cigarette tubes...

2013-04-01

355

27 CFR 40.351 - Cigarette papers.  

Code of Federal Regulations, 2012 CFR

...AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.351 Cigarette papers....

2012-04-01

356

27 CFR 41.34 - Cigarette papers.  

Code of Federal Regulations, 2013 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.34 Cigarette papers. Cigarette...

2013-04-01

357

27 CFR 40.352 - Cigarette tubes.  

...AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.352 Cigarette...

2014-04-01

358

27 CFR 40.352 - Cigarette tubes.  

Code of Federal Regulations, 2011 CFR

...AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.352 Cigarette...

2011-04-01

359

27 CFR 40.351 - Cigarette papers.  

Code of Federal Regulations, 2013 CFR

...AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.351 Cigarette papers....

2013-04-01

360

27 CFR 40.351 - Cigarette papers.  

...AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes Taxes § 40.351 Cigarette papers....

2014-04-01

361

27 CFR 41.34 - Cigarette papers.  

Code of Federal Regulations, 2011 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Tax Rates § 41.34 Cigarette papers. Cigarette...

2011-04-01

362

Origin of the bimodal distribution of low-pressure metal-organic-vapor-phase-epitaxy grown InGaAs\\/GaAs quantum dots  

Microsoft Academic Search

The formation process of a bimodal distribution of low-pressure metal-organic-vapor-phase-epitaxy (LP-MOVPE) grown InGaAs\\/GaAs quantum dots (QDs) is studied by transmission electronic microscopy. We demonstrate that in our growth conditions, the deposition of an InGaAs layer on an already existing array of InAs formed QDs leads to the nucleation of a second dots population. The InAs QDs nucleation is diffusion limited,

G. Saint-Girons; G. Patriarche; A. Mereuta; I. Sagnes

2002-01-01

363

High quality GaN layers grown by hydride vapor phase epitaxy — a high resolution X-ray diffractometry and synchrotron X-ray topography study  

Microsoft Academic Search

GaN films of different thicknesses grown on 6H-SiC (00.1) by hydride vapor-phase epitaxy(HVPE) method were characterized by high resolution X-ray diffractometry and synchrotron X-ray topography. Calculations of thermal stresses gave approximately same results as experimental stress indicating that most of the stress in the film is due to the difference in thermal expansion coefficient between the film and substrate. The

J Chaudhuri; C Ignatiev; S Stepanov; D Tsvetkov; A Cherenkov; V Dmitriev; Z Rek

2000-01-01

364

High Output Power InGaN Ultraviolet Light-Emitting Diodes Fabricated on Patterned Substrates Using Metalorganic Vapor Phase Epitaxy  

Microsoft Academic Search

Ultraviolet (UV) light-emitting diodes (LEDs) with an InGaN multi-quantum-well (MQW) structure were fabricated on a patterned sapphire substrate (PSS) using a single growth process of metalorganic vapor phase epitaxy. In this study, the PSS with parallel grooves along the sapphire direction was fabricated by standard photolithography and subsequent reactive ion etching (RIE). The GaN layer grown by lateral epitaxy on

Kazuyuki Tadatomo; Hiroaki Okagawa; Youichiro Ohuchi; Takashi Tsunekawa; Yoshiyuki Imada; Munehiro Kato; Tsunemasa Taguchi; H. Kudo

2001-01-01

365

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

366

Effect of impregnation protocol on physical characteristics and adsorptive properties of sulfur impregnated carbon for vapor-phase mercury  

SciTech Connect

Removal efficiency of commercially available sulfur-impregnated carbon (HGR) and bituminous coal-based activated carbon impregnated with sulfur at 250 C, 400 C and 600 C (BPL-S) for vapor-phase elemental mercury was evaluated under various process conditions. Based on the fixed-bed breakthrough experiments, both HGR and BPL-S carbon exhibited improved mercury removal efficiency compared to the virgin carbon (BPL). However, the BPL-S series had higher mercury uptake capacity than that of HGR for the influent mercury concentration of 55 g/m{sup 3} and at the operating temperature of 140 C. For the BPL-S series, impregnation temperature was an important factor which affected the capacity for mercury uptake. BPL-S impregnated at 600 C (BPL-S-600) had the highest removal capacity, while BPL-S-400 exhibited slightly lower capacity. BPL-S-250 exhibited significantly lower capacity when compared to BPL-S-600 and BPL-S-400. The actual sulfur content for HGR and BPL-S series were almost the same (10%), except BPL-S-250 which had much higher sulfur content of 36%. Specific surface area, as determined by the BET method, and bonding between sulfur and carbon, as determined by thermogravimetric analysis (TGA), were also dependent on the impregnation procedure. Higher impregnation temperatures promote more uniform distribution of low molecular weight sulfur allotropes on the carbon surface. Pore size distribution study showed the detailed micro-structure of these activated carbons. Most of the pores of HGR carbon have radius between 15--24 , while the radius of BPL-S pores was between 15--35 . As the impregnation temperature decreases, the portion of larger pores also decreases from BPL-S-600 to BPL-S-250.

Liu, W.; Korpiel, J.A.; Vidic, R.D. [Univ. of Pittsburgh, PA (United States). Dept. of Civil and Environmental Engineering

1997-12-31

367

The influence of sapphire substrate orientation on crystalline quality of GaN films grown by hydride vapor phase epitaxy  

NASA Astrophysics Data System (ADS)

GaN films were grown by hydride vapor phase epitaxy on sapphire substrates with orientations c-(0 0 0 1), a-(1 1 2bar 0), m-(1 0 1bar 0) and r-(1 0 1bar 2) using N 2 as a carrier gas. The crystalline perfection of the grown films was studied by X-ray diffraction, by optical microscopy and scanning electron microscopy and by microcathodoluminescence (MCL). It was found that, for c- and a-oriented sapphire substrates, the GaN films showed (0 0 0 1) orientation, for m-oriented sapphire the films showed semi-polar (1 0 1bar 3) orientation, while for r-sapphire substrates GaN layers with non-polar a(1 1 2bar 0) orientation could be grown. The surface morphology of the GaN films and their crystalline structure strongly depended on the substrate orientation. With increasing the layer thickness the halfwidth of the X-ray rocking curves monotonically decreased which points to improvement of the crystalline quality. The best quality films were grown for the c- and r-oriented substrates: respectively, 460 arcseconds at the thickness of 400 mm, 600 arcseconds at the thickness of 300 ?m. For m-oriented substrates the halfwidth was 1300 arcseconds at comparable thickness. The density of stacking faults for semi-polar and non-polar films was determined by MCL imaging. The linear density of stacking faults was found to be 5×10 4 cm -1 for films grown on m-oriented sapphire substrates and 5103 cm -1 for a-GaN films grown on r-sapphire.

Govorkov, Anatolij; Donskov, Alexsandr; Diakonov, Lev; Kozlova, Yulia; Malahov, Sergej; Markov, Alexsandr; Mezhennyi, Mikhail; Pavlov, Vladimir; Polykov, Alexsandr; Yugova, Tatiana

2009-12-01

368

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

369

The effect of state cigarette tax increases on cigarette sales, 1955 to 1988.  

PubMed Central

We evaluated the effect of state cigarette tax increases on cigarette sales in the 50 states for the years 1955 to 1988. State cigarette tax increases were associated with an average decline in cigarette consumption of three cigarette packs per capita (about 2.4%). Larger tax increases were associated with larger declines in consumption. Raising state cigarette taxes appears to be an effective public health intervention that can reduce cigarette consumption and its associated health consequences. PMID:1536343

Peterson, D E; Zeger, S L; Remington, P L; Anderson, H A

1992-01-01

370

Dynamical Jahn-Teller effects in the near ultraviolet vapor phase absorption spectra of perrhenyl chloride, ReO3Cl, and pertechnyl chloride, TcO3Cl  

Microsoft Academic Search

The near ultraviolet vapor phase absorption spectra of perrhenyl chloride and pertechnyl chloride have been observed over a range of vapor pressures and path lengths. There are several similarities in the overall features of the spectra for the two molecules. Each spectrum shows evidence of two electronic transitions at wavelengths greater than 2000 Å the longer wave-length band system of

Alan Guest; Helen Elaine Howard-Lock; Colin James Lyne Lock

1978-01-01

371

Sample introduction with graphite furnace electrothermal vaporization into an inductively coupled plasma: effects of streaming conditions and gaseous phase additives  

NASA Astrophysics Data System (ADS)

A laboratory-made graphite furnace electrothermal vaporizer (GF-ETV) was applied with two alternative versions of the exit part. In one of the versions the vapor streams upward through the transverse hole of the longitudinally heated tube (upward streaming: UPS), while with the other version the vapor streams toward one of the ends of the tube (end-on streaming: ENS). Volatile (Cd, Zn) and medium volatile elements (Cu, Mg, Mn) were applied in multi-element solutions, in the mass range of 4-10 ?g for each analyte. Net line intensities were compared for the two versions, and also for applying toluene or carbon tetrachloride vapor in the furnace atmosphere. Using pure argon as the internal furnace gas, the line intensities of the medium volatile elements Cu and Mg were lower for the ENS than for the UPS by approximately 40%. This was in agreement with findings of other authors for similar systems, and was explained by condensation of vapors on cooler parts of the graphite tube, close to the outlet end. On the other hand, the UPS and ENS provided similar line intensities for Cu and Mg when CCl 4 vapor (0.5% v/v) was used in the internal furnace gas as a result of the formation of volatile chlorides, which do not condense in the graphite tube. Recently published transport efficiency data, including our own results, are evaluated with respect of design characteristics, operating conditions, applied analytes and chemical modifiers/carriers.

Kántor, Tibor

2000-05-01

372

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

373

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

374

Genetic effects of fresh cigarette smoke in Saccharomyces cerevisiae.  

PubMed

Ability of fresh cigarette smoke from University of Kentucky reference cigarette 2R1 to induce gene conversion, reverse mutation and mitotic crossing-over in strain D7 of Saccharomyces cerevisiae was examined. A closed cell suspension-recycle system using 2 peristaltic pumps interconnected to a single-port reverse-phase smoking machine was developed to provide complete exposure of cells to smoke within 0.2--10 sec of its generation. The exposed cells showed a dose-dependent increase in the frequency of all the 3 genetic endpoints examined. Cell age was an important factor with younger cells being more sensitive than older. Filtration studies showed that the gas phase possessed as much as 25% of the total whole-smoke activity. Activated charcoal reduced the activity of smoke in direct proportion to its amount in the filter. Acetate filter did not appreciably alter the activity. A comparison of whole smoke from various cigarettes showed that: (1) the nicotine content of a cigarette does not affect the genetic activity of smoke; (2) burley and flue-cured tobaccos have differential activity in gene conversion and reverse mutation systems; and (3) the genetic effects of whole smoke are not peculiar to tobacco pyrolysis because similar effects are produced by smokes from lettuce and other non-tobacco cigarettes. It is concluded that the yeast D7 system can be used effectively for the quantitative evaluation of genetic effects of smoke from different cigarettes, and both whole cigarette smoke and its gas phase possess mutagenic as well as recombinogenic activity that can be modified by the use of filters. PMID:6755230

Gairola, C

1982-09-01

375

Geographic patterns of cigarette butt waste in the urban environment  

PubMed Central

Background This reports the initial phase of a study to quantify the spatial pattern of cigarette butt waste in an urban environment. Methods Geographic Information Systems (GIS) was used to create a weighted overlay analysis model which was then applied to the locations of businesses where cigarettes are sold or are likely to be consumed and venues where higher concentrations of butts may be deposited. The model's utility was tested using a small-scale litter audit in three zip codes of San Diego, California. Results We found that cigarette butt waste is highly concentrated around businesses where cigarettes are sold or consumed. The mean number of butts for predicted high waste sites was 38.1 (SD 18.87), for predicted low waste sites mean 4.8 (SD 5.9), p<0.001. Conclusions Cigarette butt waste is not uniformly distributed in the urban environment, its distribution is linked to locations and patterns of sales and consumption. A GIS and weighted overlay model may be a useful tool in predicting urban locations of greater and lesser amounts of cigarette butt waste. These data can in turn be used to develop economic cost studies and plan mitigation strategies in urban communities. PMID:21504924

Novotny, Thomas E

2011-01-01

376

Sampling and analysis of cigarette smoke using the solid adsorbent Tenax  

SciTech Connect

The commercial introduction of ultra-low-tar delivery cigarette products has posed challenges in the analysis of their smoke constituents. The application of solid sorbent trapping and thermal desorption, programmed-temperature glass-capillary-column gas chromatography has proven useful for both gas phase and particulate matter analyses. In gas phase analysis the cigarette is smoked directly through a Cambridge filter and Tenax trap, and in whole smoke analysis through the Tenax trap alone. For cigarettes having deliveries of < 1 mg tar/cigarette the entire trap content, or a fraction thereof, is desorbed at 250/sup 0/C in the injection port of the gas chromatograph, and the cryothermally trapped organic desorbate is separated by programmed temperature gas chromatography. Tenax used to trap smoke from higher tar delivery cigarettes is duluted with clean Tenax and homogenized before analysis. Quantitation is made by the method of external standards, the RSD for smoke components averaging generally +-20%. Higher RSD's of +-60% in the case of some ultra-low cigarette smoke components may be influenced by mainstream enrichment by sidestream smoke drifting near the air dilution vents in the filter rod. This method of analysis when applied to whole smoke can determine the entire cigarette delivery of many gas phase and particulate matter components, and has sufficient sensitivity that flavor related components in cigarette smoke are analyzable. The distribution of some semivolatile components between gas and particulate phases has been determined by application of this method and is reported.

Higgins, C.E.; Griest, W.H.; Guerin, M.R.

1984-05-01

377

THE PRICE OF CIGARETTES AND THE PROFITS OF CIGARETTE MANUFACTURERS WITH AND WITHOUT  

E-print Network

of cigarettes and the profits of the domestic tobacco-producing divisions of U.S. cigarette manufacturers. I remain high. There are no close substitutes for cigarettes as a product. Other tobacco productsTHE PRICE OF CIGARETTES AND THE PROFITS OF CIGARETTE MANUFACTURERS WITH AND WITHOUT FEDERAL

Gabrieli, John

378

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

379

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

380

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

381

Experimental and textural investigation of welding: effects of compaction, sintering, and vapor-phase crystallization in the rhyolitic Rattlesnake Tuff  

NASA Astrophysics Data System (ADS)

The abrupt changes in character of variably welded pyroclastic deposits have invited decades of investigation and classification. We conducted two series of experiments using ash from the nonwelded base of the rhyolitic Rattlesnake Tuff of Oregon, USA, to examine conditions of welding. One series of experiments was conducted at atmospheric pressure (1 At) in a muffle furnace with variable run times and temperature and another series was conducted at 5 MPa and 600 °C in a cold seal apparatus with variable run times and water contents. We compared the results to a suite of incipiently to densely welded, natural samples of the Rattlesnake Tuff. Experiments at 1 At required a temperature above 900 °C to produce welding, which is in excess of the estimated pre-eruptive magmatic temperature of the tuff. The experiments also yielded globular clast textures unlike the natural tuff. During the cold-seal experiments, the gold sample capsules collapsed in response to sample densification. Textures and densities that closely mimic the natural suite were produced at 5 MPa, 600 °C and 0.4 wt.% H 2O, over run durations of hours to 2 days. Clast deformation and development of foliation in 2-week runs were greater than in natural samples. Both more and less water reduced the degree of welding at otherwise constant run conditions. For 5 MPa experiments, changes in the degree of foliation of shards and of axial ratios of bubble shards and non-bubble (mainly platy) shards, are consistent with early densification related to compaction and partial rotation of shards into a foliation. Subsequent densification was associated with viscous deformation as indicated by more sintered contacts and deformation of shards. Sintering (local fusion of shard-shard contacts) was increasingly important with longer run times, higher temperatures, and greater pressures. During runs with high water concentrations, sintering was rare and adhesion between clasts was dominated by precipitation of sublimates in pore spaces. A few tenths wt.% H 2O in the rhyolite glass promote the development of welding by sharp reduction of glass viscosity. Large amounts of water inhibit welding by creating surface sublimates that interfere with sintering and may exert fluid pressure counter to lithostatic load if sintering and vapor-phase sublimates seal permeability in the tuff.

Grunder, Anita L.; Laporte, Didier; Druitt, Tim H.

2005-04-01

382

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

383

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

384

Youths' understandings of cigarette advertisements.  

PubMed

This study addresses two questions: (1) when youths are exposed to advertisements for cigarettes, do they primarily see advertisements for brands or products, and (2) is there a relationship between youths' understandings of cigarette advertisements and their susceptibility to smoking? A sample of 271 participants ranging in age from 7 to 12 viewed a series of print advertisements that included cigarette and non-tobacco-related ads. While viewing each ad, participants were asked to indicate what they thought the advertisement was trying to sell. Responses were coded into one of three categories reflecting important differences in participants' comprehension of each advertisement - no understanding, product category understanding, or brand understanding. Results show that youths typically understand the type of product an advertisement is promoting; however, the levels of brand understanding observed for cigarette advertisements were low in an absolute sense, and significantly lower than brand understanding of non-tobacco-related advertisements. Results also show that understanding cigarette ads as promoting specific brands of cigarettes is positively related to susceptibility to smoking. Taken together, these findings provide a glimpse of the psychological mechanisms that may underlie the well established link between exposure to cigarette advertising and youth smoking. PMID:18812253

Freeman, Dan; Brucks, Merrie; Wallendorf, Melanie; Boland, Wendy

2009-01-01

385

Waterpipe Tobacco and Cigarette Smoking  

Microsoft Academic Search

Methods: Participants (N31; M21.4 years, SD2.3) reporting monthly waterpipe use (M5.2 uses\\/month, SD4.0) and weekly cigarette smoking (M9.9 cigarettes\\/day, SD6.4) completed a crossover study in which they each smoked a waterpipe for a maximum of 45 minutes, or a single cigarette. Outcome measures included expired-air carbon monoxide (CO) 5 minutes after session's end, and blood carboxyhemoglobin (COHb), plasma nicotine, heart

Thomas Eissenberg; Alan Shihadeh

2009-01-01

386

The effect of cigarette taxes on cigarette consumption.  

PubMed Central

OBJECTIVES: This paper reexamines the work of Meier and Licari in a previous issue of the Journal. METHODS: The impact of excise taxes on cigarette consumption and sales was measured via standard regression analysis. RESULTS: The 1983 federal tax increase is shown to have an anomalous effect on the regression results. When those data are excluded, there is no significant difference between state and federal tax increases. Further investigation suggests that firms raised cigarette prices substantially in the years surrounding the 1983 federal tax increase, which accounts for the relatively large decrease in consumption during this period. CONCLUSIONS: Federal excise taxes per se do not appear to be more effective than state excise taxes in terms of reducing cigarette consumption. The reaction of cigarette firms to government policies appears to be an important determinant of the success of antismoking initiatives. PMID:9663167

Showalter, M H

1998-01-01

387

Decreased respiratory symptoms in cannabis users who vaporize  

PubMed Central

Cannabis smoking can create respiratory problems. Vaporizers heat cannabis to release active cannabinoids, but remain cool enough to avoid the smoke and toxins associated with combustion. Vaporized cannabis should create fewer respiratory symptoms than smoked cannabis. We examined self-reported respiratory symptoms in participants who ranged in cigarette and cannabis use. Data from a large Internet sample revealed that the use of a vaporizer predicted fewer respiratory symptoms even when age, sex, cigarette smoking, and amount of cannabis used were taken into account. Age, sex, cigarettes, and amount of cannabis also had significant effects. The number of cigarettes smoked and amount of cannabis used interacted to create worse respiratory problems. A significant interaction revealed that the impact of a vaporizer was larger as the amount of cannabis used increased. These data suggest that the safety of cannabis can increase with the use of a vaporizer. Regular users of joints, blunts, pipes, and water pipes might decrease respiratory symptoms by switching to a vaporizer PMID:17437626

Earleywine, Mitch; Barnwell, Sara Smucker

2007-01-01

388

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

389

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

390

Incorporating Phase-Dependent Polarizability in Non-Additive Electrostatic Models for Molecular Dynamics Simulations of the Aqueous Liquid-Vapor Interface.  

PubMed

We discuss a new classical water force field that explicitly accounts for differences in polarizability between liquid and vapor phases. The TIP4P-QDP (4-point transferable intermolecular potential with charge dependent-polarizability) force field is a modification of the original TIP4P-FQ fluctuating charge water force field of Rick et al.(1) that self-consistently adjusts its atomic hardness parameters via a scaling function dependent on the M-site charge. The electronegativity (?) parameters are also scaled in order to reproduce condensed-phase dipole moments of comparable magnitude to TIP4P-FQ. TIP4P-QDP is parameterized to reproduce experimental gas-phase and select condensed-phase properties. The TIP4P-QDP water model possesses a gas phase polarizability of 1.40 Å(3) and gas-phase dipole moment of 1.85 Debye, in excellent agreement with experiment and high-level ab initio predictions. The liquid density of TIP4P-QDP is 0.9954(±0.0002) g/cm(3) at 298 K and 1 atmosphere, and the enthalpy of vaporization is 10.55(±0.12) kcal/mol. Other condensed-phase properties such as the isobaric heat capacity, isothermal compressibility, and diffusion constant are also calculated within reasonable accuracy of experiment and consistent with predictions of other current state-of-the-art water force fields. The average molecular dipole moment of TIP4P-QDP in the condensed phase is 2.641(±0.001) Debye, approximately 0.02 Debye higher than TIP4P-FQ and within the range of values currently surmised for the bulk liquid. The dielectric constant, ? = 85.8 ± 1.0, is 10% higher than experiment. This is reasoned to be due to the increase in the condensed phase dipole moment over TIP4P-FQ, which estimates ? remarkably well. Radial distribution functions for TIP4P-QDP and TIP4P-FQ show similar features, with TIP4P-QDP showing slightly reduced peak heights and subtle shifts towards larger distance interactions. Since the greatest effects of the phase-dependent polarizability are anticipated in regions with both liquid and vapor character, interfacial simulations of TIP4P-QDP were performed and compared to TIP4P-FQ, a static polarizability analog. Despite similar features in density profiles such as the position of the GDS and interfacial width, enhanced dipole moments are observed for the TIP4P-QDP interface and onset of the vapor phase. Water orientational profiles show an increased preference (over TIP4P-FQ) in the orientation of the permanent dipole vector of the molecule within the interface; an enhanced z-induced dipole moment directly results from this preference. Hydrogen bond formation is lower, on average, in the bulk for TIP4P-QDP than TIP4P-FQ. However, the average number of hydrogen bonds formed by TIP4P-QDP in the interface exceeds that of TIP4P-FQ, and observed hydrogen bond networks extend further into the gaseous region. The TIP4P-QDP interfacial potential, calculated to be -11.98(±0.08) kcal/mol, is less favorable than that for TIP4P-FQ by approximately 2% as a result of a diminished quadrupole contribution. Surface tension is calculated within a 1.3% reduction from the experimental value. Results reported demonstrate TIP4P-QDP as a model comparable to the popular TIP4P-FQ while accounting for a physical effect previously neglected by other water models. Further refinements to this model, as well as future applications are discussed. PMID:23133341

Bauer, Brad A; Warren, G Lee; Patel, Sandeep

2009-02-10

391

Controlling the size of InAs quantum dots on Si 1? x Ge x \\/Si(0 0 1) by metalorganic vapor-phase epitaxy  

Microsoft Academic Search

The formation of III–V InAs quantum dots (QDs) on group-IV Si1?xGex\\/Si(001) was investigated by metalorganic vapor-phase epitaxy. Two types of QDs, round-shaped QDs and giant QDs elongated in the [110] or [1,?1,0] direction, were observed in a growth condition of low V\\/III ratios. An increase in the V\\/III ratio and AsH3 preflow during the cooling process was found to suppress

Kenichi Kawaguchi; Hiroji Ebe; Mitsuru Ekawa; Akio Sugama; Yasuhiko Arakawa

2009-01-01

392

Ultra-thin in InAlP\\/InGaAs heterojunctins grown by metal-organic vapor-phase epitaxy  

Microsoft Academic Search

This paper reports the metal-organic vapor-phase epitaxy (MOVPE) growth of ultra-thin InAlP\\/InGaAs heterojunctions for use as wet-etching stoppers in InP-based high electron mobility transistors (HEMTs) and as barriers in resonant tunneling diodes (RTDs). InAlP\\/InGaAs modulation-doped (MD) heterojunctions with high electron mobility were successfully grown. Practical wet-etching selectivity in even 2-nm-thick InAlP etch stoppers was demonstrated. High peak current density (jP)

Hiroki Sugiyama; Haruki Yokoyama; Naoteru Shigekawa; Takatomo Enoki; Atsushi Teranishi; Safumi Suzuki; Masahiro Asada

2009-01-01

393

Transmission electron microscopy study of the InP\\/InGaAs and InGaAs\\/InP heterointerfaces grown by metalorganic vapor-phase epitaxy  

Microsoft Academic Search

InP\\/InGaAs and InGaAs\\/InP interfaces in heterostructures grown by metalorganic vapor-phase epitaxy (MOVPE) have been studied by transmission electron microscopy (TEM). Cross-sectional TEM 002 dark field images of the direct (InP-InGaAs) and inverted (InGaAs-InP) interfaces revealed a great difference in abruptness. Whereas the direct interface is always well defined and flat, the inverted one is compositionally graded and shows surface undulations.

Jean Decobert; Gilles Patriarche

2002-01-01

394

Hydride Vapor Phase Epitaxy of GaN on NdGaO3 Substrate and Realization of Freestanding GaN Wafers with 2-inch Scale  

Microsoft Academic Search

GaN thick film is grown on NdGaO3 substrate using hydride vapor phase epitaxy. To avoid decomposition of NdGaO3 substrate by NH3, a low-temperature grown GaN protective layer is adopted. Using NdGaO3 substrate and a low-temperature GaN protective layer simultaneously, 2-inch-scale GaN wafers are realized. The photoluminescence (PL) spectrum indicates strong band-edge emission without deep-level related emission. Both plan-view transmission electron

Akihiro Wakahara; Takenori Yamamoto; Kouji Ishio; Akira Yoshida; Youji Seki; Keiji Kainosho; Osamu Oda

2000-01-01

395

1.3-{micro}m buried-heterostructure lasers using a CH{sub 4} reactive-ion-etched mesa structure grown by metalorganic vapor phase epitaxy  

SciTech Connect

This paper reports on the study of using dry etching and metalorganic vapor phase epitaxy (MOVPE) to fabricate of buried-heterostructure (BH) lasers. With a dry-etched mesa, there was anomalously large Zn diffusion into the mesa structure and it seriously degraded the lasing characteristics. Therefore, the authors inserted a buffer layer between the side wall of the dry-etched mesa and the p-InP current blocking layer. The buffer layer almost entirely eliminates Zn diffusion without changing the mesa geometry unlike the wet-etching treatment of the mesa structure. Fabricated lasers show high performance, high uniformity and good reliability.

Kondo, Y.; Kishi, K.; Itoh, M.; Oohashi, H.; Itaya, Y.; Yamamoto, M. [NTT Opto-electronics Labs., Atsugi, Kanagawa (Japan)

1996-12-31

396

Implementation of diffractive optical element in four-wave mixing scheme for ex situ characterization of hydride vapor phase epitaxy-grown GaN layers  

NASA Astrophysics Data System (ADS)

A holographic beam splitter has been integrated into a picosecond four-wave mixing (FWM) scheme. This modification significantly simplified the procedure of dynamic grating recording, thus making the FWM technique an easy-to-use tool for the holographic characterization of wide band gap materials. The novel FWM scheme was applied for characterization of hydride vapor phase epitaxy-grown undoped GaN layers of different thickness. It allowed the determination of carrier lifetime, diffusion coefficient, and carrier diffusion length by optical means, as well as the study of carrier recombination peculiarities with respect to dislocation and excess carrier density.

Jarasiunas, K.; Aleksiejunas, R.; Malinauskas, T.; Gudelis, V.; Tamulevicius, T.; Tamulevicius, S.; Guobiene, A.; Usikov, A.; Dmitriev, V.; Gerritsen, H. J.

2007-03-01

397

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

398

Gas phase photocatalytic degradation on TiOâ pellets of volatile chlorinated organic compounds from a soil vapor extraction well  

Microsoft Academic Search

The mineralization of trichloroethylene (TCE) and tetrachloroethylene (PCE) in gas stream from a soil vapor extraction (SVE) well was demonstrated with an annular photocatalytic reactor packed with porous TiOâ pellets in field trials at the Savannah River Site in Aiken, SC. The TiOâ pellets were prepared using a sol-gel method. The experiments were performed at 55 to 60°C using space

S. Yamazaki-Nishida; H. W. Read; J. K. Nagano; M. A. Anderson; S. Cervera-March; T. R. Jarosch; C. A. Eddy-Dilek

1993-01-01

399

Gas phase photocatalytic degradation on TIO2 pellets of volatile chlorinated organic compounds from a soil vapor extraction well  

Microsoft Academic Search

The degradation of trichloroethylene (TCE, Cl2C=CHCl) and tetrachloroethylene (PCE, Cl2C=CCI2) in a gas stream from a soil vapor extraction (SVE) well was demonstrated with an annular photocatalytic reactor packed with porous TiO2 pellets in a field trial at the Savannah River Site in Aiken, SC. The TiO2 pellets were prepared using a sol?gel method. The experiments were performed at 55

Harry W. Read; Joyce K. Nagano; Tim Jarosch; Carol Eddy; Marc A. Anderson

1994-01-01

400

27 CFR 40.215 - Notice for cigarettes.  

Code of Federal Regulations, 2010 CFR

... 2010-04-01 false Notice for cigarettes. 40.215 Section 40.215 Alcohol... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO... Packages § 40.215 Notice for cigarettes. Every package of cigarettes...

2010-04-01

401

27 CFR 40.23 - Cigarette tax rates.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Cigarette tax rates. 40.23 Section 40... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes § 40.23 Cigarette tax rates. Cigarettes are...

2010-04-01

402

27 CFR 41.32 - Cigarette tax rates.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Cigarette tax rates. 41.32 Section...IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED... Taxes Tax Rates § 41.32 Cigarette tax rates. Cigarettes are...

2010-04-01

403

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 broadening of the reciprocal lattice points that was measured using high-resolution X-ray diffraction as well. The fitting of the reciprocal space maps allowed the character of the threading dislocations to be described quantitatively in terms of the fractions of edge and screw dislocations. It was found that the threading dislocation density increases with increasing compressive residual stress. Furthermore, the dislocation density and the residual stress decrease with increasing thickness of the GaN layers. The edge component of the threading dislocations was dominant in all samples. Still, some differences in the character of the dislocations were observed for different templates.

Barchuk, M.; Röder, C.; Shashev, Y.; Lukin, G.; Motylenko, M.; Kortus, J.; Pätzold, O.; Rafaja, D.

2014-01-01

404

(abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary  

NASA Technical Reports Server (NTRS)

The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.

Williams, R. M.; Jeffries-Nakamura, B.; Ryan, M. A.; Underwood, M. L.; O'Connor, D.; Kikkert, S.

1993-01-01

405

19 CFR 11.3 - Package and notice requirements for cigars and cigarettes; package requirements for cigarette...  

Code of Federal Regulations, 2013 CFR

...Package and notice requirements for cigars and cigarettes; package requirements for cigarette papers and tubes. 11.3 Section 11...Package and notice requirements for cigars and cigarettes; package requirements for cigarette...

2013-04-01

406

19 CFR 11.2a - Release from Customs custody without payment of tax on cigars, cigarettes and cigarette papers...  

Code of Federal Regulations, 2012 CFR

...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. 11.2a Section 11.2a...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. Cigars,...

2012-04-01

407

19 CFR 11.3 - Package and notice requirements for cigars and cigarettes; package requirements for cigarette...  

Code of Federal Regulations, 2011 CFR

...Package and notice requirements for cigars and cigarettes; package requirements for cigarette papers and tubes. 11.3 Section 11...Package and notice requirements for cigars and cigarettes; package requirements for cigarette...

2011-04-01

408

19 CFR 11.2a - Release from Customs custody without payment of tax on cigars, cigarettes and cigarette papers...  

Code of Federal Regulations, 2013 CFR

...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. 11.2a Section 11.2a...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. Cigars,...

2013-04-01

409

19 CFR 11.3 - Package and notice requirements for cigars and cigarettes; package requirements for cigarette...  

...Package and notice requirements for cigars and cigarettes; package requirements for cigarette papers and tubes. 11.3 Section 11...Package and notice requirements for cigars and cigarettes; package requirements for cigarette...

2014-04-01

410

19 CFR 11.3 - Package and notice requirements for cigars and cigarettes; package requirements for cigarette...  

Code of Federal Regulations, 2012 CFR

...Package and notice requirements for cigars and cigarettes; package requirements for cigarette papers and tubes. 11.3 Section 11...Package and notice requirements for cigars and cigarettes; package requirements for cigarette...

2012-04-01

411

19 CFR 11.2a - Release from Customs custody without payment of tax on cigars, cigarettes and cigarette papers...  

Code of Federal Regulations, 2011 CFR

...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. 11.2a Section 11.2a...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. Cigars,...

2011-04-01

412

19 CFR 11.2a - Release from Customs custody without payment of tax on cigars, cigarettes and cigarette papers...  

...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. 11.2a Section 11.2a...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. Cigars,...

2014-04-01

413

19 CFR 11.2a - Release from Customs custody without payment of tax on cigars, cigarettes and cigarette papers...  

Code of Federal Regulations, 2010 CFR

...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. 11.2a Section 11.2a...Customs custody without payment of tax on cigars, cigarettes and cigarette papers and tubes. Cigars,...

2010-04-01

414

19 CFR 11.3 - Package and notice requirements for cigars and cigarettes; package requirements for cigarette...  

Code of Federal Regulations, 2010 CFR

...Package and notice requirements for cigars and cigarettes; package requirements for cigarette papers and tubes. 11.3 Section 11...Package and notice requirements for cigars and cigarettes; package requirements for cigarette...

2010-04-01

415

Size-dependent phase diagram of nanoscale alloy drops used in vapor--liquid--solid growth of semiconductor nanowires.  

PubMed

We use in situ observations during high-temperature transmission electron microscopy to quantify the exchange of semiconductor material between Au-Ge vapor--liquid--solid seed drops and Ge nanowires (NWs). By performing simultaneous measurements under identical conditions on arrays with systematic variations in NW diameter, we establish the nanoscale size dependence of the temperature-dependent equilibrium composition of the Au-Ge binary alloy. We find a significantly enhanced Ge solubility for drops on thin NWs compared to thicker ones. The controlled modification of the surface of the NW by an ordered carbon shell leads to drastic changes in the solubility. PMID:20731466

Sutter, Eli A; Sutter, Peter W

2010-08-24

416

Electronic cigarettes for smoking cessation.  

PubMed

Electronic cigarettes (e-cigarettes) are novel vaporising devices that, similar to nicotine replacement treatments, deliver nicotine but in lower amounts and less swiftly than tobacco smoking. However, they enjoy far greater popularity than these medications due in part to their behaviour replacement characteristics. Evidence for their efficacy as cessation aids, based on several randomised trials of now obsolete e-cigarettes, suggests a modest effect equivalent to nicotine patch. E-cigarettes are almost certainly far less harmful than tobacco smoking, but the health effects of long-term use are as yet unknown. Dual use is common and almost as harmful as usual smoking unless it leads to quitting. Population effects, such as re-normalising smoking behaviour, are a concern. Clinicians should be knowledgeable about these products. If patients who smoke are unwilling to quit or cannot succeed using evidence-based approaches, e-cigarettes may be an option to be considered after discussing the limitations of current knowledge. PMID:25303892

Bullen, Christopher

2014-11-01

417

Scrambled and fried: cigarette smoke exposure causes antral follicle destruction and oocyte dysfunction through oxidative stress.  

PubMed

Cigarette smoke is a reproductive hazard associated with pre-mature reproductive senescence and reduced clinical pregnancy rates in female smokers. Despite an increased awareness of the adverse effects of cigarette smoke exposure on systemic health, many women remain unaware of the adverse effects of cigarette smoke on female fertility. This issue is compounded by our limited understanding of the molecular mechanisms behind cigarette smoke induced infertility. In this study we used a direct nasal exposure mouse model of cigarette smoke-induced chronic obstructive pulmonary disease to characterise mechanisms of cigarette-smoke induced ovotoxicity. Cigarette smoke exposure caused increased levels of primordial follicle depletion, antral follicle oocyte apoptosis and oxidative stress in exposed ovaries, resulting in fewer follicles available for ovulation. Evidence of oxidative stress also persisted in ovulated oocytes which escaped destruction, with increased levels of mitochondrial ROS and lipid peroxidation resulting in reduced fertilisation potential. Microarray analysis of ovarian tissue correlated these insults with a complex mechanism of ovotoxicity involving genes associated with detoxification, inflammation, follicular activation, immune cell mediated apoptosis and membrane organisation. In particular, the phase I detoxifying enzyme cyp2e1 was found to be significantly up-regulated in developing oocytes; an enzyme known to cause molecular bioactivation resulting in oxidative stress. Our results provide a preliminary model of cigarette smoke induced sub-fertility through cyp2e1 bioactivation and oxidative stress, resulting in developing follicle depletion and oocyte dysfunction. PMID:23693141

Sobinoff, A P; Beckett, E L; Jarnicki, A G; Sutherland, J M; McCluskey, A; Hansbro, P M; McLaughlin, E A

2013-09-01

418

Vaporization and Autoignition Characteristics of Ethanol and 1-  

E-print Network

Vaporization and Autoignition Characteristics of Ethanol and 1- propanol Droplets: Influence vaporization, which involves heat, mass and momentum transfer processes in gas and liquid phases to improve efficiency of internal combustion engines generally. Both vaporization and autoigni- tion

Paris-Sud XI, Université de

419

Relative Ignition Propensity of Test Market Cigarettes.  

National Technical Information Service (NTIS)

The Federal Trade Commission (FTC) requested that the National Institute of Standards and Technology (NIST) conduct tests to determine whether a test market cigarette made with a slower burning paper would reduce the risk that such a cigarette, if dropped...

R. G. Gann, K. D. Steckler, S. Ruitberg, W. F. Guthrie, M. S. Levenson

2001-01-01

420

27 CFR 41.38 - Cigarettes.  

Code of Federal Regulations, 2011 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Classification of Large Cigars and Cigarettes § 41.38...

2011-04-01

421

27 CFR 41.38 - Cigarettes.  

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Classification of Large Cigars and Cigarettes § 41.38...

2014-04-01

422

27 CFR 41.38 - Cigarettes.  

Code of Federal Regulations, 2012 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Classification of Large Cigars and Cigarettes § 41.38...

2012-04-01

423

27 CFR 41.38 - Cigarettes.  

Code of Federal Regulations, 2013 CFR

...TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Taxes Classification of Large Cigars and Cigarettes § 41.38...

2013-04-01

424

Cadmium determination in cigarettes available in Nigeria  

Microsoft Academic Search

± 0.46 ?g\\/g) compared to the Nigerian brands (1.10 ± ± ± ± 0.35 ?g\\/g). Relatively lower Cd values were observed in cigarettes from developing countries (~ 1.3 ?g\\/g) compared to brands from developed countries (>1.3 ?g\\/g). The average Cd content of cigarettes available in Nigeria is 1.28 ?g per cigarette and a person who smokes 20 cigarettes per day

425

Determination of methane concentrations in water in equilibrium with sI methane hydrate in the absence of a vapor phase by in situ Raman spectroscopy  

USGS Publications Warehouse

Most submarine gas hydrates are located within the two-phase equilibrium region of hydrate and interstitial water with pressures (P) ranging from 8 to 60 MPa and temperatures (T) from 275 to 293 K. However, current measurements of solubilities of methane in equilibrium with hydrate in the absence of a vapor phase are limited below 20 MPa and 283.15 K, and the differences among these data are up to 30%. When these data were extrapolated to other P-T conditions, it leads to large and poorly known uncertainties. In this study, in situ Raman spectroscopy was used to measure methane concentrations in pure water in equilibrium with sI (structure one) methane hydrate, in the absence of a vapor phase, at temperatures from 276.6 to 294.6 (??0.3) K and pressures at 10, 20, 30 and 40 (??0.4%) MPa. The relationship among concentration of methane in water in equilibrium with hydrate, in mole fraction [X(CH4)], the temperature in K, and pressure in MPa was derived as: X(CH4) = exp [11.0464 + 0.023267 P - (4886.0 + 8.0158 P)/T]. Both the standard enthalpy and entropy of hydrate dissolution at the studied T-P conditions increase slightly with increasing pressure, ranging from 41.29 to 43.29 kJ/mol and from 0.1272 to 0.1330 kJ/K ?? mol, respectively. When compared with traditional sampling and analytical methods, the advantages of our method include: (1) the use of in situ Raman signals for methane concentration measurements eliminates possible uncertainty caused by sampling and ex situ analysis, (2) it is simple and efficient, and (3) high-pressure data can be obtained safely. ?? 2007 Elsevier Ltd. All rights reserved.

Lu, W.; Chou, I.-M.; Burruss, R.C.

2008-01-01

426

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

427

Functionalization of paraffinic hydrocarbons by heterogeneous vapor-phase oxidation III. Conversion of the C sub 2 -C sub 7 alkane series  

SciTech Connect

A new promising area of research in the field of vapor-phase heterogeneous catalysis is the functionalization of paraffinic hydrocarbons. At present, the selective oxidation of {und n}-butane to maleic anhydride is the only process which is highly selective and operative on a commercial scale. The peculiar characteristics of selectivity, the basis for interest in this reaction, are principally related to the specific nature of the active phase, vanadyl pyrophosphate. This catalyst is the only active phase discovered which is truly selective: however, the activity/selectivity is strictly related to the method of preparation. The aim of this work is to investigate if it is possible to extend the utilization of a (VO){sub 2}P{sub 2}O{sub 7} catalyst highly active/selective in {und n}-butane. Propane conversion has been studied on V-P-O catalysts where low selectivities to methanol or acrylic acid were found and on Ce-Te-Mo-O oxides doped with CdX{sub 2} (X=F, C1) that give low yields of acrolein. The aims of this paper are to explore the mild oxidation of the other alkanes using the same active phase as for {und n}-butane and to obtain a better understanding of the transformation of {und n}-butane to maleic anhydride.

Centti, G.; Trifiro, F. (Department of Industrial Chemistry and Materials, Bologna (Italy))

1987-08-01

428

Autocatalytic isomerizations of the two most stable conformers of carbonic acid in vapor phase: double hydrogen transfer in carbonic acid homodimers.  

PubMed

The cis-cis [(cc)] and cis-trans [(ct)] conformers of carbonic acid (H2CO3) are known as the two most stable conformers based on the different orientations of two OH functional groups present in the molecule. To explain the interconversion of the (cc)-conformer to its (ct)-conformer, the rotation of one of the two indistinguishable OH functional groups present in the (cc)-conformer has been shown until now as the effective isomerization mechanism. Moreover, the (ct)-conformer, which is slightly energetically disfavored over the (cc)-conformer, has been considered as the starting point for the decomposition of H2CO3 into CO2 and H2O molecules. Experimentally, on the other hand, the infrared (IR) and Raman spectroscopy of the crystalline H2CO3 polymorphs suggest that the most possible basic building blocks of H2CO3 polymorphs consist of only and exclusively the (cc)-conformers. However, the sublimations of these crystalline H2CO3 polymorphs result both the (cc)- and (ct)-conformers in the vapor phase with the (cc)-conformer being the major species. In this article, we first report the high level ab initio calculations investigating the energetics of the autocatlytic isomerization mechanism between the two most stable conformers of carbonic acid in the vapor phase. The calculations 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. The results of the present study specifically and strongly suggest that double hydrogen transfer within the eight-membered cyclic doubly hydrogen-bonded (H-bonded) ring interface of the H2CO3 homodimer formed between two (cc)-conformers is ultimately the starting mechanism for the isomerization of the (cc)-conformer to its (ct)-conformer, especially, during the sublimation of the H2CO3 polymorphs, which result in the vapor phase concentration of the (cc)-conformer at the highest levels. PMID:24878165

Ghoshal, Sourav; Hazra, Montu K

2014-07-01

429

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 ci