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1

Hot atom chemistry and radiopharmaceuticals  

SciTech Connect

The chemical products made in a cyclotron target are a combined result of the chemical effects of the nuclear transformation that made the radioactive atom and the bulk radiolysis in the target. This review uses some well-known examples to understand how hot atom chemistry explains the primary products from a nuclear reaction and then how radiation chemistry is exploited to set up the optimal product for radiosynthesis. It also addresses the chemical effects of nuclear decay. There are important principles that are common to hot atom chemistry and radiopharmaceutical chemistry. Both emphasize short-lived radionuclides and manipulation of high specific activity nuclides. Furthermore, they both rely on radiochromatographic separation for identification of no-carrieradded products.

Krohn, Kenneth A.; Moerlein, Stephen M.; Link, Jeanne M.; Welch, Michael J. [University of Washington, Department of Radiology, Molecular Imaging Center, 1959 NE Pacific St., Box 356004, Seattle, WA 98195-6004 (United States); Washington University, Department of Radiology, Division of Radiological Sciences, 510 South Kingshighway, St. Louis, MO 63110 (United States); University of Washington, Department of Radiology, Molecular Imaging Center, 1959 NE Pacific St., Box 356004, Seattle, WA 98195-6004 (United States); Washington University, Department of Radiology, Division of Radiological Sciences, 510 South Kingshighway, St. Louis, MO 63110 (United States)

2012-12-19

2

Plutonium-244, supernova and hot atom chemistry.  

NASA Astrophysics Data System (ADS)

Re-examination of a vast amount of xenon isotope data reveals that the carbonaceous chondrites and some of the lunar fines began retaining their xenon when the ratio of 244Pu to 238U in the solar system was 0.113 to 0.262 (atom/atom) about 4,900 million years ago. Excess 129Xe from the decay of 129I is conspicuously missing in most of these samples, indicating that either a) the last supernova exploded more than 150 to 200 million years prior to the time the carbonaceous chondrites began to retain their xenon, or b) fine-grained interstellar diamond crystals found in the carbonaceous chondrites may have played the role of a "fission product catcher" for a quantitative retention of 244Pu fission xenon, while allowing the excess 129Xe from the weak-beta decay of 129I to escape from the meteorites.

Kuroda, P. K.

3

HOT-ATOM CHEMISTRY OF OXYACIDS OF HALOGENS. I. BROMATE  

Microsoft Academic Search

The behavior of recoil bromine atoms arising from the (n, gamma ) ; reaction on bromate samples in various physical states was studied. The samples ; irradiated with neutrons were bromate crystals, aqueous bromate solutions, and ; anion exchange resins loaded with bromate ions. A large fraction of radioactive ; bromine atoms appeared in a chemical form of bromide which

N. Saito; I. Tomita; M. Furukawa

1959-01-01

4

Interstellar Chemistry - Hot-Ion Reactions  

NASA Astrophysics Data System (ADS)

We have explored the possible significance on interstellar chemistry of translation ally excited ions (`hot ions') produced in exothermic reactions, focusing on weaknesses that remain in existing gas-phase models of cloud chemistry. Particular instances are the lack of success in accounting for observed abundances of NH3, N2H+ and cyanopolyacetylenes. When `hot-ion' reactions are included in the ion-molecule model we obtain predicted abundances in cold clouds like TMC-1, agreeing very well with observations (to better than one order of magnitude) for virtually all smaller molecules included in the model. In particular, the discrepancies for NH3, N2H+ and cyanopolyacetylenes no longer arise. This occurs in the time regime 106.3-106.5 yr [note that this is not the time where the abundance of complex species go through a maximum (˜105.5 yr) but somewhat later] and not for very old clouds (age > 107.5 yr). If we use rate constants for hydrogen atom abstraction reactions based on current estimates of their activation energies, then the `hot-ion' reactions do not lead to a noticeable increase in the production of longer chain hydrocarbons. However, for smaller values of these activation energies (for example, those that might make the rate constants around 10-11 cm-3 s-1), such hot-ion reactions could dramatically increase the efficiency of carbon-chain building by gas-phase reactions. Therefore, these hot-ion processes may ultimately prove to be the basis of the build-up of these larger species in cold clouds. If the build-up of long chains is to be attributed to the effect of these hot-ion reactions, then the unexpectedly gradual decline in the abundances of CnH, with increasing n, is readily explained. It seems plausible to attribute the irregular variation in these abundances to the enhanced rate of ion-dipolar processes as compared with ion-non-polar reactions, although such influences are more pronounced at greater cloud ages (> 107.5 yr).

Brown, R. D.; Cragg, D. M.; Bettens, R. P. A.

1990-08-01

5

Collision Density of Hot Atoms. II  

Microsoft Academic Search

Analytical and stochastic methods are used to investigate hot-atom reactions for relatively low-energy hot atoms such as those produced by photochemical processes. Collision densities for hot atoms are presented for several reactive systems in which the reaction probability and the threshold energy are varied. Solutions for the collision density obtained by analytical methods and independently by stochastic methods were in

D. M. Chapin; M. D. Kostin

1967-01-01

6

Chemistry in the cold, warm, and hot interstellar medium  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the chemistry that occurs in the cold dense interstellar medium and as temperatures rise above standard interstellar cloud values due to star formation or other energetic processes. During the warm up to the hot core stage (100-300 K), a radical photochemistry on grain surfaces leads to the formation of complex organic molecules (COMs), which then desorb into the gas, where they are detected. At still higher temperatures, it is necessary to consider a large number of additional gas-phase reactions that become important. We emphasize a new high-temperature gas-phase network that is capable of being used in simulations of the chemistry that occurs at temperatures up to 800-1000 K. Examples are given. It is also possible that a very high temperature surface chemistry, in which species other than atomic hydrogen stick to grains via strong chemisorption forces, occurs.

Herbst, E.

2013-06-01

7

Photo-thermo-chemistry of hot atmospheres  

NASA Astrophysics Data System (ADS)

We have developed a new model to study the atmosphere of exoplanets adapted to the characteristics of the atmospheres of hot Jupiters and hot Neptunes. Such a model appears essential to interpret recent and future observations, to predict the composition and to understand the formation and the evolution of these planetary bodies. As the chemistry of nitrogen compounds is not well constrained, we investigated several sub-networks for nitrogen-bearing species and investigate their impact on the predicted abundances and spectra of HD 189733b. We present these results. An important problem of photochemicalmodels is the lack of high temperature photochemical data. In order to improve this situation, we have begun a campaign of measurement of VUV absorption cross section at high temperature for H2O, CO2 and NH3. We will present the influence of these new experimental data on the thermo-photochemicalmodel.

Venot, O.; Hébrard, E.; Agundez, M.; Dobrijevic, M.; Selsis, F.; Hersant, F.; Bounaceur, R.; Bénilan, Y.; Gazeau, M.-C.; Fray, N.; Iro, N.

2012-09-01

8

Cold Light from Hot Atoms and Molecules  

NASA Astrophysics Data System (ADS)

The introduction of rare earth atoms and molecules into lighting discharges led to great advances in efficacy of these lamps. Atoms such as Dy, Ho and Ce provide excellent radiation sources for lighting applications, with rich visible spectra, such that a suitable combination of these elements can provide high quality white light. Rare earth molecules have also proved important in enhancing the radiation spectrum from phosphors in fluorescent lamps. This paper reviews some of the current aspects of lighting research, particularly rare earth chemistry and radiation, and the associated fundamental atomic and molecular data.

Lister, Graeme; Curry, John J.

2011-05-01

9

Cold Light from Hot Atoms and Molecules  

SciTech Connect

The introduction of rare earth atoms and molecules into lighting discharges led to great advances in efficacy of these lamps. Atoms such as Dy, Ho and Ce provide excellent radiation sources for lighting applications, with rich visible spectra, such that a suitable combination of these elements can provide high quality white light. Rare earth molecules have also proved important in enhancing the radiation spectrum from phosphors in fluorescent lamps. This paper reviews some of the current aspects of lighting research, particularly rare earth chemistry and radiation, and the associated fundamental atomic and molecular data.

Lister, Graeme [OSRAM SYLVANIA, CRSL, 71 Cherry Hill Drive, Beverly, MA (United States); Curry, John J. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

2011-05-11

10

The Chemistry of Silicon in Hot Molecular Cores  

NASA Astrophysics Data System (ADS)

The gas phase chemistry of hot molecular cores is thought to depend upon the composition of evaporated ice mantle material and its subsequent gas phase reactions. We have modelled the silicon chemistry in these conditions from an SiH4 precursor and find substantial fractional abundances of SiO, H2SiO and HNSi on a timescale of a few 104 yr.

Mackay, D. D. S.

1995-02-01

11

Interstellar Alcohols and the Chemistry of Hot Cores  

NASA Astrophysics Data System (ADS)

Gas-phase methanol and ethanol have been observed in hot cores, the warm remnants of a molecular cloud in which massive star formation has recently occurred. The newborn stars heat the surrounding gas and dust, evaporating ice mantles containing alcohols which can then participate in gas-phase reactions. Model calculations show that methanol, ethanol, propanol, and butanol drive a chemistry which can form several esters and ethers; our models show that methyl ethyl ether and diethyl ether should form in detectable quantities in cores rich in methanol and ethanol. These reactions can also explain the low observed abundance of gas-phase ethanol in some hot core sources. Possible grain surface mechanisms for the formation of these alcohols will also be presented. We acknowledge support via a DOE fellowship (MEK), a NAS/NRC research associateship at NASA Ames (SBC), a SERC grant to the UMIST Astrophysics Group (TJM), and a grant from NASA's Astrophysics Theory Program (AGGMT).

Kress, M. E.; Charnley, S. B.; Tielens, A. G. G. M.; Millar, T. J.

1994-12-01

12

The early days of atomic absorption spectrometry in clinical chemistry  

Microsoft Academic Search

An account is given of the first applications of atomic absorption spectrometry in clinical chemistry. These include the determination of calcium and magnesium in blood serum and of these elements, together with a range of heavy metals, in urine.

J. B Willis

1999-01-01

13

Atomic and Molecular Clusters in Membrane Mimetic Chemistry,  

National Technical Information Service (NTIS)

Attention in this review is focused on novel chemistries developed by the use of surfactant assembly incorporated atomic and molecular clusters. Aqueous micelles, reversed micelles, microemulsions, vesicles, polymerized vesicles, monolayers, deposited org...

J. H. Fendler

1987-01-01

14

The early days of atomic absorption spectrometry in clinical chemistry  

NASA Astrophysics Data System (ADS)

An account is given of the first applications of atomic absorption spectrometry in clinical chemistry. These include the determination of calcium and magnesium in blood serum and of these elements, together with a range of heavy metals, in urine.

Willis, J. B.

1999-12-01

15

Femtosecond two-photon photoassociation of hot magnesium atoms: A quantum dynamical study using thermal random phase wavefunctions.  

PubMed

Two-photon photoassociation of hot magnesium atoms by femtosecond laser pulses, creating electronically excited magnesium dimer molecules, is studied from first principles, combining ab initio quantum chemistry and molecular quantum dynamics. This theoretical framework allows for rationalizing the generation of molecular rovibrational coherence from thermally hot atoms [L. Rybak, S. Amaran, L. Levin, M. Tomza, R. Moszynski, R. Kosloff, C. P. Koch, and Z. Amitay, Phys. Rev. Lett. 107, 273001 (2011)]. Random phase thermal wavefunctions are employed to model the thermal ensemble of hot colliding atoms. Comparing two different choices of basis functions, random phase wavefunctions built from eigenstates are found to have the fastest convergence for the photoassociation yield. The interaction of the colliding atoms with a femtosecond laser pulse is modeled non-perturbatively to account for strong-field effects. PMID:24182021

Amaran, Saieswari; Kosloff, Ronnie; Tomza, Micha?; Skomorowski, Wojciech; Paw?owski, Filip; Moszynski, Robert; Rybak, Leonid; Levin, Liat; Amitay, Zohar; Berglund, J Martin; Reich, Daniel M; Koch, Christiane P

2013-10-28

16

Presentation of Atomic Structure in Turkish General Chemistry Textbooks  

ERIC Educational Resources Information Center

|Research in science education has recognized the importance of teaching atomic structure within a history and philosophy of science perspective. The objective of this study is to evaluate general chemistry textbooks published in Turkey based on the eight criteria developed in previous research. Criteria used referred to the atomic models of…

Niaz, Mansoor; Costu, Bayram

2009-01-01

17

Presentation of Atomic Structure in Turkish General Chemistry Textbooks  

ERIC Educational Resources Information Center

Research in science education has recognized the importance of teaching atomic structure within a history and philosophy of science perspective. The objective of this study is to evaluate general chemistry textbooks published in Turkey based on the eight criteria developed in previous research. Criteria used referred to the atomic models of…

Niaz, Mansoor; Costu, Bayram

2009-01-01

18

Chemistry of hot springs along the Eastern Lau Spreading Center  

NASA Astrophysics Data System (ADS)

The Eastern Lau Spreading Center (ELSC) is the southernmost part of the back-arc spreading axis in the Lau Basin, west of the Tonga trench and the active Tofua volcanic arc. Over its 397-km length it exhibits large and systematic changes in spreading rate, magmatic/tectonic processes, and proximity to the volcanic arc. In 2005, we collected 81 samples of vent water from six hydrothermal fields along the ELSC. The chemistry of these waters varies both within and between vent fields, in response to changes in substrate composition, temperature and pressure, pH, water/rock ratio, and input from magmatic gases and subducted sediment. Hot-spring temperatures range from 229° to 363 °C at the five northernmost fields, with a general decrease to the south that is reversed at the Mariner field. The southernmost field, Vai Lili, emitted water at up to 334 °C in 1989 but had a maximum venting temperature of only 121 °C in 2005, due to waning activity and admixture of bottom seawater into the subseafloor plumbing system. Chloride varies both within fields and from one field to another, from a low of 528 mmol/kg to a high of 656 mmol/kg, and may be enriched by phase separation and/or leaching of Cl from the rock. Concentrations of the soluble elements K, Rb, Cs, and B likewise increase southward as the volcanic substrate becomes more silica-rich, especially on the Valu Fa Ridge. Iodine and ? 7Li increase southward, and ? 11B decreases as B increases, apparently in response to increased input from subducted sediment as the arc is approached. Species that decrease southward as temperature falls are Si, H 2S, Li, Na/Cl, Fe, Mn, and 87Sr/ 86Sr, whereas pH, alkalinity, Ca, and Sr increase. Oxygen isotopes indicate a higher water/rock ratio in the three systems on Valu Fa Ridge, consistent with higher porosity in more felsic volcanic rocks. Vent waters at the Mariner vent field on the Valu Fa Ridge are significantly hotter, more acid and metal-rich, less saline, and richer in dissolved gases and other volatiles, including H 2S, CO 2, and F, than the other vent fields, consistent with input of magmatic gases. The large variations in geologic and geophysical parameters produced by back-arc spreading along the ELSC, which exceed those along mid-ocean ridge spreading axes, produce similar large variations in the composition of vent waters, and thus provide new insights into the processes that control the chemistry of submarine hot springs.

Mottl, Michael J.; Seewald, Jeffrey S.; Wheat, C. Geoffrey; Tivey, Margaret K.; Michael, Peter J.; Proskurowski, Giora; McCollom, Thomas M.; Reeves, Eoghan; Sharkey, Jessica; You, C.-F.; Chan, L.-H.; Pichler, Thomas

2011-02-01

19

Nanoscale atoms in solid-state chemistry.  

PubMed

We describe a solid-state material formed from binary assembly of atomically precise molecular clusters. [Co6Se8(PEt3)6][C60]2 and [Cr6Te8(PEt3)6][C60]2 assembled into a superatomic relative of the cadmium iodide (CdI2) structure type. These solid-state materials showed activated electronic transport with activation energies of 100 to 150 millielectron volts. The more reducing cluster Ni9Te6(PEt3)8 transferred more charge to the fullerene and formed a rock-salt-related structure. In this material, the constituent clusters are able to interact electronically to produce a magnetically ordered phase at low temperature, akin to atoms in a solid-state compound. PMID:23744780

Roy, Xavier; Lee, Chul-Ho; Crowther, Andrew C; Schenck, Christine L; Besara, Tiglet; Lalancette, Roger A; Siegrist, Theo; Stephens, Peter W; Brus, Louis E; Kim, Philip; Steigerwald, Michael L; Nuckolls, Colin

2013-06-06

20

The Chemistry of Metal-Rich Hot Neptunes  

NASA Astrophysics Data System (ADS)

Neptune-mass planets with very high metallicities (100-3000 times solar) will exhibit an interesting continuum of atmospheric compositions in between the so-called “hot Neptune” and “Super Earth” exoplanet categories. If its metallicity is only slightly enhanced over solar, a Neptune-mass planet would have a photospheric composition similar to that predicted for any hydrogen-dominated, Jupiter-mass planet possessing a similar thermal structure and experiencing a similar incident stellar flux. Hydrogen-poor Super Earths, on the other hand, could have a variety of atmospheric compositions (e.g., Schaefer et al. 2011, arXiv:1108.4660), ranging from H2O-, CO2-, or N2-dominated atmospheres, to more exotic high-temperature SiO and metal-rich atmospheres, depending on the planet’s mass, evolutionary history, incident stellar flux, and effective temperature. A Neptune-mass planet can become metal rich through efficient hydrogen escape (e.g., for less-massive, close-in planets) or through inefficient accretion of H2, as has been suggested for our own solar-system “ice giant” Neptune, where carbon is enriched by 40-70 times solar (e.g., Karkoschka and Tomasko 2011, Icarus 211, 780) and oxygen may be enriched as much as 440 times solar (e.g., Lodders and Fegley 1994, Icarus 112, 368). We explore the predicted equilibrium and disequilibrium chemistry of generic hot Neptunes with metallicities varying from 1-3000 times solar and discuss observational consequences. The models are applied to the case of GJ 436b, where we find that methane will be the dominant carbon carrier until very high metallicities, near 2000x solar, at which point the planet can have roughly equal proportions of CO, H2, and CO2, with methane becoming a more minor constituent. We compare our model results with Spitzer infrared secondary-eclipse data for GJ436b. This work was supported by the NASA PATM program.

Moses, Julianne I.; Richardson, M. R.; Madhusudhan, N.; Line, M. R.; Visscher, C.; Fortney, J. J.

2012-10-01

21

A collisional-radiative average atom model for hot plasmas  

SciTech Connect

A collisional-radiative `average atom` (AA) model is presented for the calculation of opacities of hot plasmas not in the condition of local thermodynamic equilibrium (LTE). The electron impact and radiative rate constants are calculated using the dipole oscillator strengths of the average atom. A key element of the model is the photon escape probability which at present is calculated for a semi infinite slab. The Fermi statistics renders the rate equation for the AA level occupancies nonlinear, which requires iterations until the steady state. AA level occupancies are found. Detailed electronic configurations are built into the model after the self-consistent non-LTE AA state is found. The model shows a continuous transition from the non-LTE to the LTE state depending on the optical thickness of the plasma. 22 refs., 13 figs., 1 tab.

Rozsnyai, B.F.

1996-10-17

22

Pre-cometary ice composition from hot core chemistry.  

PubMed

Pre-cometary ice located around star-forming regions contains molecules that are pre-biotic compounds or pre-biotic precursors. Molecular line surveys of hot cores provide information on the composition of the ice since it sublimates near these sites. We have combined a hydrostatic hot core model with a complex network of chemical reactions to calculate the time-dependent abundances of molecules, ions, and radicals. The model considers the interaction between the ice and gas phase. It is applied to the Orion hot core where high-mass star formation occurs, and to the solar-mass binary protostar system IRAS 16293-2422. Our calculations show that at the end of the hot core phase both star-forming sites produce the same prebiotic CN-bearing molecules. However, in the Orion hot core these molecules are formed in larger abundances. A comparison of the calculated values with the abundances derived from the observed line data requires a chemically unprocessed molecular cloud as the initial state of hot core evolution. Thus, it appears that these objects are formed at a much younger cloud stage than previously thought. This implies that the ice phase of the young clouds does not contain CN-bearing molecules in large abundances before the hot core has been formed. The pre-biotic molecules synthesized in hot cores cause a chemical enrichment in the gas phase and in the pre-cometary ice. This enrichment is thought to be an important extraterrestrial aspect of the formation of life on Earth and elsewhere. PMID:16225436

Tornow, Carmen; Kührt, Ekkehard; Motschmann, Uwe

2005-10-01

23

Analytical chemistry in a new analytical hot cell facility  

Microsoft Academic Search

The Remote Analytical Laboratory is a new facility at the Idaho Chemical Processing Plant designed to handle samples from the processing of spent nuclear fuel. It consists of a cold laboratory for analyzing process make-up samples, a warm laboratory for analyzing low-level (<100 mR\\/h) radioactive samples, and a hot cell for analyzing high-level radioactive samples. The hot cell is built

M. A. Wade; F. W. Dykes; J. H. Goettsche; A. L. Lewis; P. C. Lewis; P. C. Marushia; J. A. Murphy; S. D. Reeder; D. R. Trannell; L. E. Trejo

1985-01-01

24

Infusing the Chemistry Curriculum with Green Chemistry Using Real-World Examples, Web Modules, and Atom Economy in Organic Chemistry Courses  

ERIC Educational Resources Information Center

Green chemistry is the awareness of the damaging environmental effects due to chemical research and inventions. There is emphasis on a need to include green chemistry in synthesis with atom economy in organic chemistry curriculum to ensure an environmentally conscious future generation of chemists, policy makers, health professionals and business…

Cann, Michael C.; Dickneider, Trudy A.

2004-01-01

25

Infusing the Chemistry Curriculum with Green Chemistry Using Real-World Examples, Web Modules, and Atom Economy in Organic Chemistry Courses  

ERIC Educational Resources Information Center

|Green chemistry is the awareness of the damaging environmental effects due to chemical research and inventions. There is emphasis on a need to include green chemistry in synthesis with atom economy in organic chemistry curriculum to ensure an environmentally conscious future generation of chemists, policy makers, health professionals and business…

Cann, Michael C.; Dickneider, Trudy A.

2004-01-01

26

Atomic Structure. Independent Learning Project for Advanced Chemistry (ILPAC). Unit S2.  

ERIC Educational Resources Information Center

|This unit on atomic structure is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit consists of two levels. Level one focuses on the atomic nucleus. Level two focuses on the arrangement of extranuclear electrons, approaching atomic orbitals through both electron bombardment and…

Inner London Education Authority (England).

27

Coherent anti-Stokes Raman scattering (CARS) detection or hot atom reaction product internal energy distributions  

SciTech Connect

Coherent anti-Stokes Raman spectroscopy (CARS) is being utilized to investigate the rovibrational energy distributions produced by reactive and nonreactive collisions of translationally hot atoms with simple molecules. Translationally hot H atoms are produced by ArF laser photolysis of HBr. Using CARS we have monitored, in a state-specific and time-resolved manner, rotational excitation of HBr (v = 0), vibrational excitation of HBr and H/sub 2/, rovibrational excitation of H/sub 2/ produced by the reaction H + HBr ..-->.. H/sub 2/ + Br, and Br atom production by photolysis of HBr.

Quick, C.R. Jr.; Moore, D.S.

1983-01-01

28

Basic actinide chemistry and physics research in close cooperation with hot laboratories: ACTILAB  

NASA Astrophysics Data System (ADS)

Basic research in actinide chemistry and physics is indispensable to maintain sustainable development of innovative nuclear technology. Actinides, especially minor actinides of americium and curium, need to be handled in special facilities with containment and radiation shields. To promote and facilitate actinide research, close cooperation with the facilities and sharing of technical and scientific information must be very important and effective. A three-year-program "Basic actinide chemistry and physics research in close cooperation with hot laboratories", ACTILAB, was started to form the basis of sustainable development of innovative nuclear technology. In this program, research on actinide solid-state physics, solution chemistry and solid-liquid interface chemistry is made using four main facilities in Japan in close cooperation with each other, where basic experiments with transuranium elements can be made. The 17O-NMR measurements were performed on (Pu0.91Am0.09)O2 to study the electronic state and the chemical behaviour of Am and Cm ions in electrolyte solutions was studied by distribution experiments.

Minato, K.; Konashi, K.; Fujii, T.; Uehara, A.; Nagasaki, S.; Ohtori, N.; Tokunaga, Y.; Kambe, S.

2010-03-01

29

Chemistry of Nuclear Recoil 18F Atoms. V. Mechanism and Systematics in CH3CF3  

Microsoft Academic Search

Nuclear recoil 18F atoms undergo hot F-for-F and F-for-H atomic substitution and hot F-for-CH3 and F-for-CF3 alkyl replacement reactions in CH3CF3. The primary absolute yields corresponding to these processes are 3.56 ± 0.07, 8.22 ± 0.09, 5.79 ± 0.31, and 8.5 ± 2.5 % (estimated value), respectively. The total primary hot yield for organic products is 26.1 ± 2.5 %,

Kenneth A. Krohn; Norris J. Parks; John W. Root

1971-01-01

30

Possibility of nonexistence of hot and superhot hydrogen atoms in electrical discharges  

NASA Astrophysics Data System (ADS)

Recently, the existence of extremely energetic hydrogen atoms in electrical discharges has been proposed in the literature with large controversy, from the analysis of the anomalous broadening of hydrogen Balmer lines. In this paper, the velocity distribution of H atoms and the profiles of the emitting atom lines created by the exothermic reaction H2++H2?H3++H+?E are calculated, as a function of the internal energy defect ?E . The shapes found for the non-Maxwell-Boltzmann distributions resulting in non-Gaussian line profiles raise serious arguments against the existence of hot and superhot H atoms as it has been proposed, at least with those temperatures.

Loureiro, J.; Amorim, J.

2010-09-01

31

Volatile organic compound ratios as probes of halogen atom chemistry in the Arctic  

NASA Astrophysics Data System (ADS)

Volatile organic compound concentration ratios can be used as indicators of halogen chemistry that occurs during ozone depletion events in the Arctic during spring. Here we use a combination of modeling and measurements of [acetone]/[propanal] as an indicator of bromine chemistry, and [isobutane]/[n-butane] and [methyl ethyl ketone]/[n-butane] are used to study the extent of chlorine chemistry during four ozone depletion events during the Polar Sunrise Experiment of 1995. Using a 0-D photochemistry model in which the input of halogen atoms is controlled and varied, the approximate ratio of [Br]/[Cl] can be estimated for each ozone depletion event. It is concluded that there must be an additional source of propanal (likely from the snowpack) to correctly simulate the VOC chemistry of the Arctic, and that the ratio of Br atoms to Cl atoms can vary greatly during ozone depletion events.

Cavender, A. E.; Biesenthal, T. A.; Bottenheim, J. W.; Shepson, P. B.

2007-08-01

32

Volatile organic compound ratios as probes of halogen atom chemistry in the Arctic  

NASA Astrophysics Data System (ADS)

Volatile organic compound concentration ratios can be used as indicators of halogen chemistry that occurs during ozone depletion events in the Arctic during spring. Here we use a combination of modeling and measurements of [acetone]/[propanal] as an indicator of bromine chemistry, and [isobutane]/[n-butane] and [methyl ethyl ketone]/[n-butane] are used to study the extent of chlorine chemistry during four ozone depletion events during the Polar Sunrise Experiment of 1995. Using a 0-D photochemistry model in which the input of halogen atoms is controlled and varied, the approximate ratio of [Br]/[Cl] can be estimated for each ozone depletion event. It is concluded that there must be an additional source of propanal (likely from the snowpack) to correctly simulate the VOC chemistry of the Arctic, and further evidence that the ratio of Br atoms to Cl atoms can vary greatly during ozone depletion events is presented.

Cavender, A. E.; Biesenthal, T. A.; Bottenheim, J. W.; Shepson, P. B.

2008-03-01

33

Dry soldering with hot filament produced atomic hydrogen  

DOEpatents

A system is disclosed for chemically transforming metal surface oxides to metal that is especially, but not exclusively, suitable for preparing metal surfaces for dry soldering and solder reflow processes. The system employs one or more hot, refractory metal filaments, grids or surfaces to thermally dissociate molecular species in a low pressure of working gas such as a hydrogen-containing gas to produce reactive species in a reactive plasma that can chemically reduce metal oxides and form volatile compounds that are removed in the working gas flow. Dry soldering and solder reflow processes are especially applicable to the manufacture of printed circuit boards, semiconductor chip lead attachment and packaging multichip modules. The system can be retrofitted onto existing metal treatment ovens, furnaces, welding systems and wave soldering system designs. 1 fig.

Panitz, J.K.G.; Jellison, J.L.; Staley, D.J.

1995-04-25

34

Transition wavelengths for helium atom in weakly coupled hot plasmas  

NASA Astrophysics Data System (ADS)

We have investigated the effect of surrounding plasmas on several singly excited and doubly excited meta-stable bound states of helium atom using highly correlated basis functions for singly excited S, P, D states and CI-type basis functions for doubly excited meta-stable D states. Plasma effect is taken care of by using a screened Coulomb (Yukawa) potential obtained from the Debye model that admits a variety of plasma conditions, and such a model plays an important role in plasma spectroscopy. The wavelengths for transitions from the 1snp 1P° (n=2,3)?1s21Se, 1snp 3P° (n=2,3)?1s2s 3Se, 2pnp 1Pe (n=3,4)?1s2p 1P°, 2pnp 3Pe (n=2,3)?1s2p 3P°, 2pnd 1D° (n=3,4)?1s3d 1De, 2pnd 3D° (n=3,4)?1s3d 3De, 2p3p 1Pe?2pnd 1D° (n=3,4), 2pnd 1D°(n=3, 4)?2p4p 1Pe, 2pnp 3Pe (n=2,3)?2p3d 3D°, and 2pnp 3Pe (n=2,3)?2p4d 3D° of helium atom in plasmas for various Debye lengths are reported.

Kar, Sabyasachi; Ho, Y. K.

2007-09-01

35

Single-collision studies of hot atom energy transfer and chemical reaction. Final report  

SciTech Connect

This report discusses research in the collision dynamics of translationally hot atoms, with funding with DOE for the project ``Single-Collision Studies of Hot Atom Energy Transfer and Chemical Reaction,`` Grant Number DE-FG03-85ER13453. The work reported here was done during the period September 9, 1988 through October 31, 1991. During this period this DOE-funded work has been focused on several different efforts: (1) experimental studies of the state-to-state dynamics of the H + RH {yields} H{sub 2} R reactions where RH is CH{sub 4}, C{sub 2}H{sub 6}, or C{sub 3}H{sub 8}, (2) theoretical (quasiclassical trajectory) studies of hot hydrogen atom collision dynamics, (3) the development of photochemical sources of translationally hot molecular free radicals and characterization of the high resolution CARS spectroscopy of molecular free radicals, (4) the implementation of stimulated Raman excitation (SRE) techniques for the preparation of vibrationally state-selected molecular reactants.

Valentini, J.J. [Columbia Univ., New York, NY (United States)

1991-12-31

36

Single-collision studies of hot atom energy transfer and chemical reaction  

SciTech Connect

This report discusses research in the collision dynamics of translationally hot atoms, with funding with DOE for the project Single-Collision Studies of Hot Atom Energy Transfer and Chemical Reaction,'' Grant Number DE-FG03-85ER13453. The work reported here was done during the period September 9, 1988 through October 31, 1991. During this period this DOE-funded work has been focused on several different efforts: (1) experimental studies of the state-to-state dynamics of the H + RH {yields} H{sub 2} R reactions where RH is CH{sub 4}, C{sub 2}H{sub 6}, or C{sub 3}H{sub 8}, (2) theoretical (quasiclassical trajectory) studies of hot hydrogen atom collision dynamics, (3) the development of photochemical sources of translationally hot molecular free radicals and characterization of the high resolution CARS spectroscopy of molecular free radicals, (4) the implementation of stimulated Raman excitation (SRE) techniques for the preparation of vibrationally state-selected molecular reactants.

Valentini, J.J. (Columbia Univ., New York, NY (United States))

1991-01-01

37

Chemical Principles Revisited: Updating the Atomic Theory in General Chemistry.  

ERIC Educational Resources Information Center

|Presents a descriptive overview of recent achievements in atomic structure to provide instructors with the background necessary to enhance their classroom presentations. Topics considered include hadrons, quarks, leptons, forces, and the unified fields theory. (JN)|

Whitman, Mark

1984-01-01

38

Symmetry in chemistry from the hydrogen atom to proteins  

PubMed Central

The last 2 decades have seen discoveries in highly excited states of atoms and molecules of phenomena that are qualitatively different from the “planetary” model of the atom, and the near-rigid model of molecules, characteristic of these systems in their low-energy states. A unified view is emerging in terms of approximate dynamical symmetry principles. Highly excited states of two-electron atoms display “molecular” behavior of a nonrigid linear structure undergoing collective rotation and vibration. Highly excited states of molecules described in the “standard molecular model” display normal mode couplings, which induce bifurcations on the route to molecular chaos. New approaches such as rigid–nonrigid correlation, vibrons, and quantum groups suggest a unified view of collective electronic motion in atoms and nuclear motion in molecules.

Kellman, Michael E.

1996-01-01

39

Alcohol chemistry in the Galactic Center molecular clouds. A gigantic Hot Core  

NASA Astrophysics Data System (ADS)

We have carried out a systematic study of CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO and CS in different Galactic Center (GC) molecular clouds. Figure 1 shows the relative abundances of those molecules with respect to CH3OH in the GC as function of the CH3OH abundance. The CH3OH abundance between sources in the GC varies in nearly two orders of magnitude. The abundance ratio of these molecules relative to CH3OH is basically independent of the CH3OH abundances and only varies in a factor of ~ 4 - 8. The abundance ratio of CS relative to CH3OH seem to vary by a factor of 60. Our data are compared with observations of the same molecules in short-lived objects like the hot cores. The abundance and the abundance ratios of the complex molecules relative to CH3OH in massive hot cores are similar to that found in the GC clouds. Alcohol related chemistry is believed to be driven by gas phase reactions after evaporation of alcohols from grain mantles. Gas phase chemistry based in the ejection of alcohols from grains (see Charnley et al. 1995; Horn et al. (2004)) can not explain the observed abundances of HCOOCH3 in the GC and the rather constant relative abundances of the other complex molecules. Our data suggest that basically all the molecules related to alcohol chemistry could be produced on grain mantles and/or depleted from gas phase after their formation. This interpretation requires frequent shocks in the GC region to keep the high abundances of these molecules in gas phase and a rather uniform average composition of the icy grain mantles. The molecular clouds associated with the Sickle and the Thermal Radio Arches (TRA), which seem to be affected by UV radiation, see Rodriguez-Fernandez et al. (2001), show lower abundances of C2H5OH relative to CH3OH which could be explained by shock ejection and photo dissociation conditions.

Requena Torres, M. A.; Martín-Pintado, J.; Rodríguez-Franco, A.; Martín, S.; Rodríguez-Fer?Ndez, N. J.

40

Atom-resolved surface chemistry using scanning tunneling microscopy  

NASA Astrophysics Data System (ADS)

We use scanning tunneling microscopy to investigate the reactivity of the dangling-bond states of Si(111)-(7×7). The reaction with NH3 is used as a prototype. We find that Si rest atoms are more reactive than Si adatoms and that center adatoms are more reactive than corner adatoms. Using atom-resolved electronic spectra, we probe the dangling-bond states on both clean and NH3-exposed surfaces. We find significant interactions and charge transfer between sites which strongly influence surface reactivity.

Wolkow, R.; Avouris, Ph.

1988-03-01

41

Density dependence of the atomic transition probabilities in hot, dense plasmas  

SciTech Connect

The atomic properties and transition probabilities of highly ionized aluminum in hot, dense plasmas were studied. In particular, we present computational results of the variations with density of the following atomic parameters: atomic potential and screening factor (due to both bound and free electrons), free-electron distribution, atomic wave functions, binding energies, line shifts, and, finally, transition probabilities and oscillator strengths. The calculations were carried out using the ion-sphere model (ISM) which treats the bound and free electrons in the atom self-consistently in a central potential. This potential is produced by the combination of the nuclear Coulomb field together with contributions by the bound- and free-electron charge distributions. The results indicate an increasing effect of the plasma on the atomic properties with increasing plasma density. Particularly, the free-electron screening reduces the atomic potential, pushes the atomic wave functions away from the nucleus, and reduces the binding energy of the bound electrons. The transition probability also decreases monotonically with density up to the ionization limit of the upper state beyond which it drops to zero. The computational results are compared to those expected from a homogeneous free-electron spatial distribution.

Salzmann, D.; Szichman, H.

1987-01-15

42

Atomic force microscopy study of micrometric pattern replica by hot embossing lithography  

Microsoft Academic Search

Strong PolyMethylMetAcrilate (PMMA) resist recoveries, occurring in the centre of micro-scale structures replicated by hot embossing lithography (HEL), have been evidenced after the de-moulding stage. A statistical study by atomic force microscopy clearly reveals that, for a fixed pattern size, the heights and the widths of these recoveries decrease when the imprint temperature goes up and increase with the imprint

Laurence Ressier; Christel Martin; Jean Pierre Peyrade

2004-01-01

43

Microstructural development of a gas-atomized and hot-pressed super-? 2 alloy  

Microsoft Academic Search

A variety of heat treatments have been employed to explore the microstructure in Ti-25Al-10Nb-3V-lMo alloy prepared by gas\\u000a atomization and hot pressing. These treatments include quenching by oil cooling and water cooling and aging at temperatures\\u000a between 530 C and 950 C. Quenching transformations from the ?-phase field include the formation ofO phase in oil quenching and ? (disordered) +O

R. Xu; Y. Y. Cui; D. M. Xu; D. Li; Q. C. Li; Z. Q. Hu

1996-01-01

44

Two-color ghost interference with photon pairs generated in hot atoms  

SciTech Connect

We report on an experimental observation of a two-photon ghost interference experiment. A distinguishing feature of our experiment is that the photons are generated via a non-degenerated spontaneous four-wave mixing process in a hot atomic ensemble; therefore the photon has narrow bandwidth. Besides, there is a large difference in frequency between two photons in a pair. Our works may be important to achieve more secure, large transmission capacity long-distance quantum communication.

Ding Dongsheng; Zhou Zhiyuan; Shi Baosen; Zou Xubo; Guo Guangcan [Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026 (China)

2012-09-15

45

Progress Report (1980-1982) for the Chemistry Division, Bhabha Atomic Research Centre, Bombay, India.  

National Technical Information Service (NTIS)

The research and development (R and D) activities of the Chemistry Division of the Bhabha Atomic Research Centre, Bombay, during the period 1980-1982 are reported in the form of summaries. Basic research activities are being carried out in the areas of in...

R. P. Patel Prithvi Raj

1983-01-01

46

Progress toward atomic layer epitaxy of diamond using radical chemistry  

NASA Astrophysics Data System (ADS)

A method for atomic layer epitaxy (ALE) of diamond using radical reactants under medium vacuum conditions is being developed. Precursor molecules are injected into a stream of thermally-dissociated fluorine atoms, generating radicals in a chemically specific way. We have grown diamond particles at rates of approximately 0.1 micrometers/hr on polycrystalline copper and nickel wire substrates seeded by diamond particles from continuous flows of F/F2, H2, and C2H3 or CH4 at substrate temperatures of 500-600 C and reactor pressures between 10(exp-3) and 10(exp-1) Torr. Identification of diamond with submicron lateral resolution was made using electron microprobe x-ray fluorescence wavelength dispersive spectroscopy.

Gat, R.; Hukka, T. I.; Develyn, M. P.

1993-05-01

47

The coordination and atom transfer chemistry of titanium porphyrin complexes  

SciTech Connect

Preparation, characterization, and reactivity of ({eta}{sup 2}- alkyne)(meso-tetratolylpoprphrinato)titanium(II) complexes are described, along with inetermetal oxygen atom transfer reactions involving Ti(IV) and Ti(III) porphyrin complexes. The {eta}{sup 2}- alkyne complexes are prepared by reaction of (TTP)TiCl{sub 2} with LiAlH{sub 4} in presence of alkyne. Structure of (OEP)Ti({eta}{sup 2}-Ph-C{triple_bond}C-Ph) (OEP=octaethylporphryin) was determined by XRD. The compounds undergo simple substitution to displace the alkyne and produce doubly substituted complexes. Structure of (TTP)Ti(4-picoline){sub 2} was also determined by XRD. Reaction of (TTP)Ti{double_bond}O with (OEP)Ti-Cl yields intermetal O/Cl exchange, which is a one-electron redox process mediated by O atom transfer. Also a zero-electron redox process mediated by atom transfer is observed when (TTP)TiCl{sub 2} is reacted with (OEP)Ti{double_bond}O.

Hays, J.A.

1993-11-05

48

Environmentally protected hot-stage atomic force microscope for studying thermo-mechanical deformation in microelectronic devices  

Microsoft Academic Search

A commercial atomic force microscope (AFM) was equipped with a hot stage for conducting thermal cycling experiments up to 398 K, as well as a vacuum and purge system to provide a protective environment during heating. Two different hot-stage configurations, one for studying features in the plane of a microelectronic device, and the other for studying features on its cross

T. E. Shultz; I. Dutta

2004-01-01

49

Beating the density limit by continuously loading a dipole trap from millikelvin-hot magnesium atoms  

NASA Astrophysics Data System (ADS)

We load 105 magnesium atoms in a dipole trap from a millikelvin-hot magneto-optical trap (MOT) using a continuous-loading scheme. Light-assisted two-body processes limit the maximum achievable density in a MOT, resulting in a reduced transfer efficiency into a dipole trap when using the conventional sequential scheme. It is overcome in a continuous-loading scheme where a loss channel is opened in the MOT. This allows the accumulation of atoms in the dipole trap over the trap lifetime, determined by collisions with the background gas. This results in a significantly higher number of trapped atoms even at a lower steady-state peak density in the MOT.

Riedmann, M.; Kelkar, H.; Wübbena, T.; Pape, A.; Kulosa, A.; Zipfel, K.; Fim, D.; Rühmann, S.; Friebe, J.; Ertmer, W.; Rasel, E.

2012-10-01

50

All-atomic generation and noise-quadrature filtering of squeezed vacuum in hot Rb vapor  

NASA Astrophysics Data System (ADS)

With our all-atomic squeezing and filtering setup, we demonstrate control over the noise amplitudes and manipulation of the frequency-dependent squeezing angle of a squeezed vacuum quantum state by passing it through an atomic medium with electromagnetically induced transparency (EIT). We generate low sideband frequency squeezed vacuum using the polarization self-rotation effect in a hot Rb vapor cell, and input it into a second atomic vapor subject to EIT conditions. We use the frequency-dependent absorption of the EIT window to demonstrate an example of squeeze amplitude attenuation and squeeze angle rotation of the quantum noise quadratures of the squeezed probe. These studies have implications for quantum memory and storage as well as gravitational wave interferometric detectors.

Horrom, Travis; Romanov, Gleb; Novikova, Irina; Mikhailov, Eugeniy E.

2013-01-01

51

Measurement of the Impact of Halogen Atom Chemistry on Volatile Organic Compounds in the Arctic  

NASA Astrophysics Data System (ADS)

It is well known that ozone and mercury depletion events occur in the Arctic during spring, around the time of polar sunrise. It has been suggested that halogen atoms, in particular bromine, play an important role in the onset of these depletion events, during which chlorine chemistry is also occurring. A variety of carbonyl compounds are produced when chlorine atoms react with VOCs, and destruction of aldehydes is seen as a result of bromine atom chemistry. Thus, these two halogen atoms impact the distribution of carbonyl compounds, and the ketone/aldehyde ratio is sensitive to the levels of chlorine and bromine that are present. During a field study in Barrow, Alaska, January - March of 2005, a variety of alkanes, ketones and aldehydes were measured using a preconcentrating autosampler-gas chromatograph-mass spectrometer from an inland site, and via Tenax-based sampling and GC-FID analysis in the vicinity of the Barrow lead. Additionally, ambient samples were collected in canisters and analyzed off-site, and the results from those canisters were used to evaluate the data collected with the instruments mentioned above. Here we discuss what can be learned about the sources and reactions of these compounds by examining the relationships between these species and ozone during a time period ranging from pre-polar sunrise, when ozone is not depleted, to post-polar sunrise, when substantial surface halogen chemistry is occurring.

Cavender, A.; Tackett, P.; Keil, A.; Shepson, P.; Young, V.

2005-12-01

52

Atomic theories of phyllosilicates: Quantum chemistry, statistical mechanics, electrostatic theory, and crystal chemistry  

Microsoft Academic Search

This paper is a review atomic-level studies of phyllosilicates. Included are quantum chemical, crystal chemical, electrostatic, and statistical mechanical investigations. Five themes are proposed for future research: short-range water-clay, clay-clay, and ion-clay potentials; structure of defects and edges; structure and properties of interlayer water; chemical reaction and phyllosilicate edges; and electron transfer and transport. 106 refs., 3 figs., 5 tabs.

William F. Bleam

1993-01-01

53

Physics and chemistry in the process of hot-wire deposition of thin film silicon  

NASA Astrophysics Data System (ADS)

Hotwire Chemical Vapor Deposition (CVD) has been used in preparing high quality low hydrogen content hydrogenated amorphous or polycrystalline silicon thin film in recent years. Comparing to the most commonly used glow discharge method, Hotwire CVD has the potential of high speed deposition avoiding the damage caused by ion bombardment associated with plasma. Although device quality thin films have been prepared by this method, and some empirical optimized deposition conditions have been established, the mechanisms controlling this technique are not clear. A homebuild threshold ionization mass spectrometer was constructed in this lab, allowing the radicals to be observed with high sensitivity. Hydrogen dissociation on the hot metal surface was studied first both by the direct detection of hydrogen atoms from the hot surface and the temperature change due to the hydrogen dissociation, it was confirmed that the activation energy of this process is around 2.25eV, the same as the dissociation in the gas phase. Further, we observed a first order dependence of hydrogen dissociation probability on the hydrogen pressure. This observation contradicts previously reported models of second order desorption. The monosilicon radicals Si and SiH3 were observed. It was observed that the silane decomposition on the hot surface is mainly a function of filament temperature, but the species released from that surface also depend on the surface condition, and thus on the silane exposure history of that piece of filament. Si is believed to deteriorate the film quality, by comparing the depleted silane and the Si flux, it is observed that Si experienced a lot of gas phase reactions before reaching the substrate, which leads to less reactive precursors. This observation is consistence with Molenbroek's study on the optimization of deposition condition. The dominant disilicon radical is identified as Si2H2, which in the form of lowest energy isomer, is suppose to be much less reactive than Si, and thus contributes to good quality thin film deposition. The corresponding Si insert reaction Si + SiH4 was also studied and an effective reaction coefficient of KSeff = 5 x 10-12( cm3/s was established.

Zheng, Wengang

54

Nonequilibrium processes in reactions of hot tritium atoms with cooled solid targets. Influence of the atomizer temperature on formation of labeled substances  

Microsoft Academic Search

A system consisting of a cold target and “hotatoms generated by dissociation of tritium on a tungsten wire was studied with\\u000a the aim to determine conditions for preparing tritium-labeled organic compounds with the maximal radiochemical yield. The\\u000a influence of the atomizer temperature on the result of the reaction of tritium atoms with amino acids and tetraalkylammonium\\u000a bromides was studied;

M. G. Chernysheva; G. A. Badun; Z. A. Tyasto; V. Yu. Pozdnyakova; V. M. Fedoseev; A. L. Ksenofontov

2007-01-01

55

Research and citation impact of publications by the Chemistry Division at Bhabha Atomic Research Centre  

Microsoft Academic Search

The paper analyses the citations to 1733 publications published during 1970–1999 by the Chemistry Division at Bhabha Atomic\\u000a Research Centre, using Science Citation Index 1982–2003 as the source data. The extent of citations received, in terms of\\u000a the number of citations per paper, yearwise break up of citations, domainwise citations, self-citations and citations by others,\\u000a diachronous self-citation rate, citing authors,

B. S. Kademani; Vijai Kumar; Ganesh Surwase; Anil Sagar; Lalit Mohan; Anil Kumar; C. R. Gaderao

2007-01-01

56

Chemistry of the heaviest elements--one atom at a time  

SciTech Connect

In keeping with the goal of the Viewpoint series of the Journal of Chemical Education, this article gives a 75-year perspective of the chemistry of the heaviest elements, including a 50-year retrospective view of past developments, a summary of current research achievements and applications, and some predictions about exciting, new developments that might be envisioned within the next 25 years. A historical perspective of the importance of chemical separations in the discoveries of the transuranium elements from neptunium (Z=93) through mendelevium (Z=101) is given. The development of techniques for studying the chemical properties of mendelevium and still heavier elements on the basis of measuring the radioactive decay of a single atom (''atom-at-a-time'' chemistry) and combining the results of many separate experiments is reviewed. The influence of relativistic effects (expected to increase as Z{sup 2}) on chemical properties is discussed. The results from recent atom-at-a-time studies of the chemistry of the heaviest elements through seaborgium (Z=106) are summarized and show that their properties cannot be readily predicted based on simple extrapolation from the properties of their lighter homologues in the periodic table. The prospects for extending chemical studies to still heavier elements than seaborgium are considered and appear promising.

Hoffman, Darleane C.; Lee, Diana M.

2000-01-01

57

Generating Molecular Rovibrational Coherence by Two-Photon Femtosecond Photoassociation of Thermally Hot Atoms  

SciTech Connect

The formation of diatomic molecules with rotational and vibrational coherence is demonstrated experimentally in free-to-bound two-photon femtosecond photoassociation of hot atoms. In a thermal gas at a temperature of 1000 K, pairs of magnesium atoms, colliding in their electronic ground state, are excited into coherent superpositions of bound rovibrational levels in an electronically excited state. The rovibrational coherence is probed by a time-delayed third photon, resulting in quantum beats in the UV fluorescence. A comprehensive theoretical model based on ab initio calculations rationalizes the generation of coherence by Franck-Condon filtering of collision energies and partial waves, quantifying it in terms of an increase in quantum purity of the thermal ensemble. Our results open the way to coherent control of a binary reaction.

Rybak, Leonid; Levin, Liat; Amitay, Zohar [Shirlee Jacobs Femtosecond Laser Research Laboratory, Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Amaran, Saieswari; Kosloff, Ronnie [Institute of Chemistry, Hebrew University, Jerusalem 91904 (Israel); Tomza, Michal; Moszynski, Robert [Department of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw (Poland); Koch, Christiane P. [Institut fuer Theoretische Physik, Freie Universitaet Berlin, Arnimallee 14, 14195 Berlin (Germany); Theoretische Physik, Universitaet Kassel, Heinrich-Plett-Strasse 40, 34132 Kassel (Germany)

2011-12-30

58

Generating Molecular Rovibrational Coherence by Two-Photon Femtosecond Photoassociation of Thermally Hot Atoms  

NASA Astrophysics Data System (ADS)

The formation of diatomic molecules with rotational and vibrational coherence is demonstrated experimentally in free-to-bound two-photon femtosecond photoassociation of hot atoms. In a thermal gas at a temperature of 1000 K, pairs of magnesium atoms, colliding in their electronic ground state, are excited into coherent superpositions of bound rovibrational levels in an electronically excited state. The rovibrational coherence is probed by a time-delayed third photon, resulting in quantum beats in the UV fluorescence. A comprehensive theoretical model based on ab initio calculations rationalizes the generation of coherence by Franck-Condon filtering of collision energies and partial waves, quantifying it in terms of an increase in quantum purity of the thermal ensemble. Our results open the way to coherent control of a binary reaction.

Rybak, Leonid; Amaran, Saieswari; Levin, Liat; Tomza, Micha?; Moszynski, Robert; Kosloff, Ronnie; Koch, Christiane P.; Amitay, Zohar

2011-12-01

59

Four-wave-mixing stopped light in hot atomic rubidium vapour  

NASA Astrophysics Data System (ADS)

Digital signal processing, holography, and quantum and classical information processing rely heavily upon recording the amplitude and phase of coherent optical signals. One method for achieving coherent information storage makes use of electromagnetically induced transparency. Storage is achieved by compressing the optical pulse using the steep dispersion of the electromagnetically induced transparency medium and then mapping the electric field to local atomic quantum-state superpositions. Here we show that nonlinear optical processes may enhance pulse compression and storage, and that information about the nonlinear process itself may be stored coherently. We report on a pulse storage scheme in hot atomic rubidium vapour, in which a four-wave-mixing normal mode is stored using a double-? configuration. The entire (broadened) waveform of the input signal is recovered after several hundred microseconds (1/e time of about 120 µs), as well as a new optical mode (idler) generated from the four-wave-mixing process.

Camacho, Ryan M.; Vudyasetu, Praveen K.; Howell, John C.

2009-02-01

60

Aspects of the physical chemistry of polymers, biomaterials and mineralised tissues investigated with atomic force microscopy (AFM)  

Microsoft Academic Search

Beyond being merely a tool for measuring surface topography, atomic force microscopy (AFM) has made significant contributions to various scientific areas dealing with physical chemistry processes. This paper presents aspects of the physical chemistry at surfaces and interfaces of polymers, biomaterials and tissues investigated with AFM. Selected examples presented include surface induced self-assembly of polymer blends, copolymer interfacial reinforcement of

Klaus D Jandt; Manuela Finke; Paola Cacciafesta

2000-01-01

61

Demystifying Introductory Chemistry. Part 4: An Approach to Reaction Thermodynamics through Enthalpies, Entropies, and Free Energies of Atomization.  

ERIC Educational Resources Information Center

|Presents an alternative approach to teaching reaction thermodynamics in introductory chemistry courses using calculations of enthalpies, entropies, and free energies of atomization. Uses a consistent concept, that of decomposition of a compound to its gaseous atoms, to discuss not only thermodynamic parameters but also equilibrium and…

Spencer, James N.; And Others

1996-01-01

62

Chemistry  

NSDL National Science Digital Library

Finds ChemEd DL resources related to the sections of the General Chemistry textbook, Chemistry, by Kenneth W. Whitten, Raymond E. Davis, M. Larry Peck, George G. Stanley published by Brooks/Cole, 2010.

63

Analytical Chemistry Laboratory (ACL) procedure compendium. Volume 7, Safety operation procedure for hot cell  

SciTech Connect

This volume contains the interim change notice for the safety operation procedure for hot cell. It covers the master-slave manipulators, dry waste removal, cell transfers, hoists, cask handling, liquid waste system, and physical characterization of fluids.

Not Available

1993-08-01

64

Chemistry of the Spring Waters of the Ouachita Mountains Excluding Hot Springs, Arkansas.  

National Technical Information Service (NTIS)

Chemical analysis of the waters from 93 springs and 9 wells in the Ouachita Mountains (excluding Hot Springs), Arkansas, are reported. The study was carried out to investigate groundwater quality, its subsurface temperature, and its potential as a mineral...

G. H. Wagner K. F. Steele

1980-01-01

65

Identification of parameters through which surface chemistry determines the lifetimes of hot electrons in small Au nanoparticles  

PubMed Central

This paper describes measurements of the dynamics of hot electron cooling in photoexcited gold nanoparticles (Au NPs) with diameters of ?3.5 nm, and passivated with either a hexadecylamine or hexadecanethiolate adlayer, using ultrafast transient absorption spectroscopy. Fits of these dynamics with temperature-dependent Mie theory reveal that both the electronic heat capacity and the electron–phonon coupling constant are larger for the thiolated NPs than for the aminated NPs, by 40% and 30%, respectively. Density functional theory calculations on ligand-functionalized Au slabs show that the increase in these quantities is due to an increased electronic density of states near the Fermi level upon ligand exchange from amines to thiolates. The lifetime of hot electrons, which have thermalized from the initial plasmon excitation, increases with increasing electronic heat capacity, but decreases with increasing electron–phonon coupling, so the effects of changing surface chemistry on these two quantities partially cancel to yield a hot electron lifetime of thiolated NPs that is only 20% longer than that of aminated NPs. This analysis also reveals that incorporation of a temperature-dependent electron–phonon coupling constant is necessary to adequately fit the dynamics of electron cooling.

Aruda, Kenneth O.; Tagliazucchi, Mario; Sweeney, Christina M.; Hannah, Daniel C.; Schatz, George C.; Weiss, Emily A.

2013-01-01

66

Effects of atomic chlorine wall recombination: Comparison of a plasma chemistry model with experiment  

SciTech Connect

Results from a plasma chemistry model provide predictions of spatially and temporally averaged plasma properties. Application of the model to chlorine-etch process conditions, typical of a high plasma-density transformer coupled plasma reactor, provides plasma composition dependence on reactor operating parameter such as power and pressure. Model results also show the dependence of species concentrations on the atomic-chlorine recombination rate at reactor walls. Comparison of model predictions to measured composition trends as determined by Langmuir probe, actinometry, and ion-energy analysis reveals a critical wall-recombination probability of about 0.1 for chlorine atoms on a chlorinated anodized-aluminum surface. At or above this critical value, the model reproduces the experimentally observed trends, while employing a recombination probability below this value results in predictions that are inconsistent with the data. The model determines gas-phase and surface-species compositions in plasma-etch reactors through the solution of species, mass, electron-energy, and surface-site conservation equations. The use of well mixed reactor approximations reduces the computational expense of detailed kinetics calculations and allows investigation into the dependence of plasma chemistry on uncertain kinetic parameters. The dominance of surface reaction rates in determining plasma properties is expected to be equally important in more complex two-dimensional inductively coupled plasma models due to the highly diffuse nature of these low-pressure reactors. {copyright} {ital 1995} {ital American} {ital Vacuum} {ital Society}

Meeks, E.; Shon, J.W. [Sandia National Laboratories, Livermore, California 94551-0969 (United States); Ra, Y.; Jones, P. [Lam Research Corporation, Fremont, California 94538-6401 (United States)

1995-11-01

67

Basic actinide chemistry and physics research in close cooperation with hot laboratories: ACTILAB  

Microsoft Academic Search

Basic research in actinide chemistry and physics is indispensable to maintain sustainable development of innovative nuclear technology. Actinides, especially minor actinides of americium and curium, need to be handled in special facilities with containment and radiation shields. To promote and facilitate actinide research, close cooperation with the facilities and sharing of technical and scientific information must be very important and

K. Minato; K. Konashi; T. Fujii; A. Uehara; S. Nagasaki; N. Ohtori; Y. Tokunaga; S. Kambe

2010-01-01

68

Mass spectrometry of atomic and molecular anions from a hot-cathode plasma  

NASA Astrophysics Data System (ADS)

Atomic and molecular anions are produced in a hot-cathode discharge, anions are extracted through an aperture in the anode, and negative ion mass spectrometry is employed as a plasma diagnostic. The mass spectrometer samples the volume density of anions in the discharge near the anode. The discharge has a typical pressure of 0.1 Torr, a typical electron emission current of 5 mA, and a bombarding voltage of 75-150 V. The 2-keV beam of anions is mass-filtered by a Wien filter and detected in a Faraday cup. Typical mass-selected ion currents range from pA to tens of nA. The mass spectrometer has a section which allows interrogation of the mass-selected ion beam by a coaxial laser beam for laser photodetachment studies. Our laboratory can handle toxic and explosive source gases, e.g., hydrogen azide (HN_3) or diazomethane (CH_2N_2). Chloride (Cl^-) is readily detected: indeed, trace amounts of ^35Cl^- and ^37Cl^- are almost always present, and serve as convenient calibrating ions in the mass spectrum. Supported by DOE EPSCoR

Mitchell, Stephen E.; Farley, John W.

1999-10-01

69

Hot-atom versus Eley-Rideal dynamics in hydrogen recombination on Ni(100). I. The single-adsorbate case.  

PubMed

We compare the efficiency of the Eley-Rideal (ER) reaction with the formation of hot-atom (HA) species in the simplest case, i.e., the scattering of a projectile off a single adsorbate, considering the Hydrogen and Hydrogen-on-Ni(100) system. We use classical mechanics and the accurate embedded diatomics-in-molecules potential to study the collision system over a wide range of collision energies (0.10-1.50 eV), both with a rigid and a nonrigid Ni substrate and for impact on the occupied and neighboring empty cells. In the rigid model metastable and truly bound hot-atoms occur and we find that the cross section for the formation of bound hot-atoms is considerably higher than that for the ER reaction over the whole range of collision energies examined. Metastable hot-atoms form because of the inefficient energy transfer to the adsorbate and have lifetimes of the order 0.1-0.7 ps, depending on the collision energy. When considering the effects of lattice vibrations we find, on average, a consistent energy transfer to the substrate, say 0.1-0.2 eV, which forced us to devise a two-step dynamical model to get rid of the problems associated with the use of periodic boundary conditions. Results for long-lived HA formation due to scattering on the occupied cell at a surface temperature of 120 K agree well with those of the rigid model, suggesting that in the above process the substrate plays only a secondary role and further calculations at surface temperatures of 50 and 300 K are in line with these findings. However, considerably high cross sections for formation of long-lived hot-atoms result also from scattering off the neighboring cells where the energy transfer to the lattice cannot be neglected. Metastable hot-atoms are reduced in number and have usually lifetimes shorter than those of the rigid-model, say less than 0.3 ps. In addition, ER cross sections are only slightly affected by the lattice motion and show a little temperature dependence. Finally, we find also that absorption and reflection strongly depend on the correct consideration of lattice vibrations and the occurrence of trapping. PMID:15267808

Martinazzo, R; Assoni, S; Marinoni, G; Tantardini, G F

2004-05-01

70

Surface modification of nanoporous 1,2-polybutadiene by atom transfer radical polymerization or click chemistry.  

PubMed

Surface-initiated atom transfer radical polymerization (ATRP) and click chemistry were used to obtain functional nanoporous polymers based on nanoporous 1,2-polybutadiene (PB) with gyroid morphology. The ATRP monolith initiator was prepared by immobilizing bromoester initiators onto the pore walls through two different methodologies: (1) three-step chemical conversion of double bonds of PB into bromoisobutyrate, and (2) photochemical functionalization of PB with bromoisobutyrate groups. Azide functional groups were attached onto the pore walls before click reaction with alkynated MPEG. Following ATRP-grafting of hydrophilic polyacrylates and click of MPEG, the originally hydrophobic samples transformed into hydrophilic nanoporous materials. The successful modification was confirmed by infrared spectroscopy, contact angle measurements and measurements of spontaneous water uptake, while the morphology was investigated by small-angle X-ray scattering and transmission electron microscopy. PMID:20099923

Guo, Fengxiao; Jankova, Katja; Schulte, Lars; Vigild, Martin E; Ndoni, Sokol

2010-02-01

71

Peripheral heme substituents control the hydrogen-atom abstraction chemistry in cytochromes P450  

PubMed Central

We elucidate the hydroxylation of camphor by cytochrome P450 with the use of density functional and mixed quantum mechanics/molecular mechanics methods. Our results reveal that the enzyme catalyzes the hydrogen-atom abstraction step with a remarkably low free-energy barrier. This result provides a satisfactory explanation for the experimental failure to trap the proposed catalytically competent high-valent heme Fe(IV) oxo (oxyferryl) species responsible for this hydroxylation chemistry. The primary and previously unappreciated contribution to stabilization of the transition state is the interaction of positively charged residues in the active-site cavity with carboxylate groups on the heme periphery. A similar stabilization found in dioxygen binding to hemerythrin, albeit with reversed polarity, suggests that this mechanism for controlling the relative energetics of redox-active intermediates and transition states in metalloproteins may be widespread in nature.

Guallar, Victor; Baik, Mu-Hyun; Lippard, Stephen J.; Friesner, Richard A.

2003-01-01

72

Peripheral heme substituents control the hydrogen-atom abstraction chemistry in cytochromes P450  

NASA Astrophysics Data System (ADS)

We elucidate the hydroxylation of camphor by cytochrome P450 with the use of density functional and mixed quantum mechanics/molecular mechanics methods. Our results reveal that the enzyme catalyzes the hydrogen-atom abstraction step with a remarkably low free-energy barrier. This result provides a satisfactory explanation for the experimental failure to trap the proposed catalytically competent high-valent heme Fe(IV) oxo (oxyferryl) species responsible for this hydroxylation chemistry. The primary and previously unappreciated contribution to stabilization of the transition state is the interaction of positively charged residues in the active-site cavity with carboxylate groups on the heme periphery. A similar stabilization found in dioxygen binding to hemerythrin, albeit with reversed polarity, suggests that this mechanism for controlling the relative energetics of redox-active intermediates and transition states in metalloproteins may be widespread in nature.

Guallar, Victor; Baik, Mu-Hyun; Lippard, Stephen J.; Friesner, Richard A.

2003-06-01

73

Study of gas-phase chemistry in a hot-wire chemical vapor deposition reactor with trimethylsilane and hexamethyldisilane  

NASA Astrophysics Data System (ADS)

Gas-phase chemistry involved in the decomposition of trimethylsilane and hexamethyldisilane (HMDS) on a hot tungsten filament and the secondary gas-phase reactions in a HWCVD reactor has been studied using vacuum ultraviolet laser single photon ionization in tandem with TOF-MS. On the hot W filament, trimethylsilane is decomposed into (CH3)2HSi and CH3 radicals and HMDS is decomposed into (CH3)5Si2, CH3, and (CH3)3Si radicals. Biradical combination reactions among primary radicals and those later formed are found to be the main gas-phase reaction pathways in the reactor for both precursors. Characteristic reactions of trimethylsilane are those with (CH3)2HSi and (CH3)2HSiCH2 radicals directly or indirectly involved, resulting in the formation of peaks at m/z = 88, 118, 132, 146, 116 and 130. With relatively heavier radicals generated from the decomposition of HMDS, the characteristic reactions for HMDS are believed to be those producing peaks in higher mass region, such as peaks at m/z = 204, 218, 262, 276, and 290.

Eustergerling, Brett; Li, Xinmao; Shi, Yujun

2007-06-01

74

Chemistry  

NSDL National Science Digital Library

Chemistry is the scientific study of matter and its interaction with other matter and with energy. It is the branch of natural science that deals with the composition of substances and their properties and reactions.

K-12 Outreach,

75

Analysis of the Essential Nutrient Strontium in Marine Aquariums by Atomic Absorption Spectroscopy: An Undergraduate Analytical Chemistry Laboratory Exercise  

Microsoft Academic Search

An undergraduate atomic absorption spectroscopy (AAS) laboratory experiment is presented involving the analysis of the essential nutrient strontium in a real-life sample, sea water. The quantitative analysis of strontium in sea water is a problem well suited for an undergraduate analytical chemistry laboratory. Sea water contains numerous components which prevent the direct quantitative determination of strontium. Students learn first hand

Laurent D. Gilles de Pelichy; Carl Adam; Eugene T. Smith

1997-01-01

76

The Use of Gas Chromatography and Mass Spectrometry to Introduce General Chemistry Students to Percent Mass and Atomic Mass Calculations  

ERIC Educational Resources Information Center

|A general chemistry laboratory experiment is described that introduces students to instrumental analysis using gas chromatography-mass spectrometry (GC-MS), while simultaneously reinforcing the concepts of mass percent and the calculation of atomic mass. Working in small groups, students use the GC to separate and quantify the percent composition…

Pfennig, Brian W.; Schaefer, Amy K.

2011-01-01

77

Getting Physical with Your Chemistry: Mechanically Investigating Local Structure and Properties of Surfaces with the Atomic Force Microscope  

ERIC Educational Resources Information Center

|Atomic force microscope (AFM) investigates mechanically the chemical properties of individual molecules, surfaces, and materials using suitably designed probes. The current state of the art of AFM in terms of imaging, force measurement, and sample manipulation and its application to physical chemistry is discussed.|

Heinz, William F.; Hoh, Jan H.

2005-01-01

78

Kinematics and chemistry of the hot core in G20.08-0.14N  

NASA Astrophysics Data System (ADS)

We present Submillimeter Array (SMA) observations of the the massive star-forming region G20.08-0.14N at 335 and 345 GHz. With the SMA data, 41 molecular transitions were detected related to 11 molecular species and their isotopologues, including SO2, SO, C34S, NS, C17O, SiO, CH3OH, HC3N, H13CO+, HCOOCH3 and NH2CHO. In G20.08-0.14N, 10 transition lines out of the 41 detected belong to SO2, which dominates the appearance of the submillimetre-wave spectrum. To obtain the spatial kinematic distribution of molecules in G20.08-0.14N, we chose the strongest and unblended lines for the channel maps. The channel maps of C34S and SiO, together with their position-velocity diagrams, show that there are two accretion flows in G20.08-0.14N. Additionally, SiO emission shows a collimated outflow in the north-east-south-west direction. The direction of the outflow is revealed for the first time. The rotational temperature and column density of CH3OH are 105 K and 3.1 × 1017 cm-2, respectively. Our results confirm that a hot core is associated with G20.08-0.14N. The hot core is heated by a protostar radiation at its centre, not by external excitation from shocks. Images of the spatial distribution of different species have shown that the different molecules are located at different positions of the hot core. By comparing the spatial distributions and abundances of molecules, we discuss possible chemical processes for producing the complex sulphur-bearing, nitrogen-bearing and oxygen-bearing molecules in G20.08-0.14N.

Xu, Jin-Long; Wang, Jun-Jie

2013-05-01

79

Microelectrode studies of interstitial water chemistry and photosynthetic activity in a hot spring microbial mat  

SciTech Connect

Microelectrodes were used to measure oxygen, pH, and oxygenic photosynthetic activity in a hot spring microbial mat (Octopus Spring, Yellowstone National Park), where the cyanobacterium Synechoccus lividus and the filamentous bacteria Chloroflexus aurantiacus are the only known phototrophs. The data showed very high biological activities in the topmost layers of the microbial mat, resulting in extreme values for oxygen and pH. At a 1-mm depth at a 55 C site, oxygen and pH reached 900 micro M and 9.4, respectively, just after solar noon, whereas anoxic conditions with pH of 7.2 were measured before sunrise. Although diurnal changes between these extremes occurred over hours during a diurnal cycle microbial activity was great enough to give the same response in 1 to 2 mm after artificial shading. Oxygenic photosynthesis was confined to a 0.5- to 1.1-mm layer at sites with temperatures at or above about 50 C, with maximum activities in the 55 to 60 C region. The data suggest that S. lividus is the dominant primary producer of the mat. 30 references, 5 figures.

Revsbech, N.P.; Ward, D.M.

1984-08-01

80

Quasiclassical study of Eley-Rideal and hot atom reactions of H atoms with Cl adsorbed on a Au(111) surface  

NASA Astrophysics Data System (ADS)

Using quasiclassical methods and a potential energy surface based on total energy calculations, we have found that H atoms react with Cl atoms adsorbed onto a Au(111) surface to produce HCl via Eley-Rideal (ER), hot atom (HA), and Langmuir-Hinschelwood (LH) pathways. We observe two ER mechanisms. At small normal incidence energies reaction results from a more or less direct collision with Cl, leading to a large amount of product vibration (?=8), and relatively cold rotation and translation. In the second mechanism, more dominant at near-normal incidence and/or large incident energies, the H atom passes near Cl, recoils from the metal, and is pulled into orbit about Cl. This leads to broader product state distributions, and a more even distribution of the 3.0 eV of available energy among the product degrees of freedom, similar to products formed via the HA pathway. Overall, ER processes tend to contribute less than 10% to the reactivity, and most of the HCl is formed via HA processes. There is an increase in HCl formation with surface temperature for both the ER and HA mechanisms, but this increase is relatively weak. We observe typically about 12% H atom sticking, which would lead to HCl formation via a LH process in the experiments, above 140 K. We observe a weak forward scattering due to the direct ER component, as in the experiments. However, unlike the experiments, we observe a dip in our product angular distributions about ?f=0°, which we ascribe to our quasiclassical approximation. While we tend to see more energy in the hot products than in the experiments, our product translational, rotational, and vibrational distributions are in relatively reasonable agreement with those measured. One major disagreement with experiment is that there is apparently a significant sticking of the H atom at low temperatures, leading to a large LH component. In addition, the ER and HA components increase much more strongly with temperature than in the calculations. It is possible that electon-hole pair excitations in the metal strongly relax both the H atom and the excited HCl molecules formed.

Quattrucci, Joseph G.; Jackson, Bret

2005-02-01

81

Quasiclassical study of Eley-Rideal and hot atom reactions of H atoms with Cl adsorbed on a Au(111) surface.  

PubMed

Using quasiclassical methods and a potential energy surface based on total energy calculations, we have found that H atoms react with Cl atoms adsorbed onto a Au(111) surface to produce HCl via Eley-Rideal (ER), hot atom (HA), and Langmuir-Hinschelwood (LH) pathways. We observe two ER mechanisms. At small normal incidence energies reaction results from a more or less direct collision with Cl, leading to a large amount of product vibration (nu=8), and relatively cold rotation and translation. In the second mechanism, more dominant at near-normal incidence and/or large incident energies, the H atom passes near Cl, recoils from the metal, and is pulled into orbit about Cl. This leads to broader product state distributions, and a more even distribution of the 3.0 eV of available energy among the product degrees of freedom, similar to products formed via the HA pathway. Overall, ER processes tend to contribute less than 10% to the reactivity, and most of the HCl is formed via HA processes. There is an increase in HCl formation with surface temperature for both the ER and HA mechanisms, but this increase is relatively weak. We observe typically about 12% H atom sticking, which would lead to HCl formation via a LH process in the experiments, above 140 K. We observe a weak forward scattering due to the direct ER component, as in the experiments. However, unlike the experiments, we observe a dip in our product angular distributions about thetaf=0 degrees, which we ascribe to our quasiclassical approximation. While we tend to see more energy in the hot products than in the experiments, our product translational, rotational, and vibrational distributions are in relatively reasonable agreement with those measured. One major disagreement with experiment is that there is apparently a significant sticking of the H atom at low temperatures, leading to a large LH component. In addition, the ER and HA components increase much more strongly with temperature than in the calculations. It is possible that electon-hole pair excitations in the metal strongly relax both the H atom and the excited HCl molecules formed. PMID:15743263

Quattrucci, Joseph G; Jackson, Bret

2005-02-15

82

KfK, Institut fuer Heisse Chemie. Ergebnisbericht ueber Forschungs- und Entwicklungsarbeiten 1990. (KfK, Institute of Hot Chemistry. Progress report on research and development activities in 1990).  

National Technical Information Service (NTIS)

The activities undertaken by the hot chemistry laboratory (IHCH) in 1990 under the following projects are presented: (1) Radioactive waste management (basic work on reprocessing technologies); (2) pollutant control in the environment (communal waste manag...

1991-01-01

83

Temperature and concentration distribution of H2 and H atoms in hot-filament chemical-vapor deposition of diamond  

NASA Astrophysics Data System (ADS)

The temperature and concentration distributions of hydrogen in a hot-filament chemical-vapor deposition reactor of diamond have been measured simultaneously by coherent anti-Stokes Raman scattering (CARS). The bright background from the filaments was rejected by using CARS and gating on the detector as well as spatial filtering. The CARS spectra provided direct and accurate measurements of the H2 temperature and concentration distributions. The concentration distribution of atomic hydrogen was also determined by assuming a constant pressure condition and equilibrium between translational and rotational degrees of freedom in the system. It was found that the H-atom distribution departed substantially from the thermal equilibrium prediction except very near the filament; however, a diffusion-controlled model predicted the slope of this distribution throughout the measured region.

Chen, Kuei-Hsien; Chuang, Mei-Chen; Penney, Murray C.; Banholzer, William F.

1992-02-01

84

Doing Chemistry  

NSDL National Science Digital Library

This website includes over 150 chemistry experiments in the following areas: Atomic Structure, Bonding, Chemical Reactions, Colligative Properties, Condensed States, Electrochemistry, Equilibrium Gases, Instrumentation, Limiting Reactant and more.

Brooks, David W.

2010-05-25

85

Ultraslow Group Velocity and Enhanced Nonlinear Optical Effects in a Coherently Driven Hot Atomic Gas  

Microsoft Academic Search

We report the observation of small group velocities of order 90 m\\/s and large group delays of greater than 0.26 ms, in an optically dense hot rubidium gas ( ~360 K). Media of this kind yield strong nonlinear interactions between very weak optical fields and very sharp spectral features. The result is in agreement with previous studies on nonlinear spectroscopy

Michael M. Kash; Vladimir A. Sautenkov; Alexander S. Zibrov; L. Hollberg; George R. Welch; Mikhail D. Lukin; Yuri Rostovtsev; Edward S. Fry; Marlan O. Scully

1999-01-01

86

Detection of hot muonic hydrogen atoms emitted in vacuum using x-rays  

SciTech Connect

Negative muons are stopped in solid layers of hydrogen and neon. Muonic hydrogen atoms can drift to the neon layer where the muon is immediately transferred. It was found that the time structure of the muonic neon X-rays follows the exponential law where the rate is the same as the disappearance rate of [mu][sup -]p atoms. The pp[mu]-formation rate and the muon transfer rate to deuterium are deduced.

Jacot-Guillarmod, R. (Fribourg Univ. (Switzerland)); Bailey, J.M. (Liverpool Univ. (United Kingdom)); Beer, G.A.; Knowles, P.E.; Mason, G.R.; Olin, A. (Victoria Univ., BC (Canada)); Beveridge, J.L.; Marshall, G.M. (TRIUMF, Vancouver, BC (Canada)); Brewer, J.H.; Forster, B.M. (British Columbia Univ., Vancouver, BC (Canada)); Huber, T.M. (Gustavus Adolphus Coll., St. Peter, MN (United States)); Kammel, P

1992-01-01

87

Detection of hot muonic hydrogen atoms emitted in vacuum using x-rays  

SciTech Connect

Negative muons are stopped in solid layers of hydrogen and neon. Muonic hydrogen atoms can drift to the neon layer where the muon is immediately transferred. It was found that the time structure of the muonic neon X-rays follows the exponential law where the rate is the same as the disappearance rate of {mu}{sup -}p atoms. The pp{mu}-formation rate and the muon transfer rate to deuterium are deduced.

Jacot-Guillarmod, R. [Fribourg Univ. (Switzerland); Bailey, J.M. [Liverpool Univ. (United Kingdom); Beer, G.A.; Knowles, P.E.; Mason, G.R.; Olin, A. [Victoria Univ., BC (Canada); Beveridge, J.L.; Marshall, G.M. [TRIUMF, Vancouver, BC (Canada); Brewer, J.H.; Forster, B.M. [British Columbia Univ., Vancouver, BC (Canada); Huber, T.M. [Gustavus Adolphus Coll., St. Peter, MN (United States); Kammel, P.; Zmeskal, J. [Oesterreichische Akademie der Wissenschaften, Vienna (Austria). Inst. fuer Mittelenergiephysik; Kunselman, A.R. [Wyoming Univ., Laramie, WY (United States); Petitjean, C. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1992-12-31

88

Competition of silene/silylene chemistry with free radical chain reactions using 1-methylsilacyclobutane in the hot-wire chemical vapor deposition process.  

PubMed

The gas-phase reaction chemistry of using 1-methylsilacyclobutane (MSCB) in the hot-wire chemical vapor deposition (CVD) process has been investigated by studying the decomposition of MSCB on a heated tungsten filament and subsequent gas-phase reactions in a reactor. Three pathways exist to decompose MSCB on the filament to form ethene/methylsilene, propene/methylsilylene, and methyl radicals. The activation energies for forming propene and methyl radical, respectively, are determined to be 68.7 ± 1.3 and 46.7 ± 2.5 kJ·mol(-1), which demonstrates the catalytic nature of the decomposition. The secondary gas-phase reactions in the hot-wire CVD reactor are characterized by the competition between a free radical chain reaction and the cycloaddition of silene reactive species produced either from the primary decomposition of MSCB on the filament or the isomerization of silylene species. At lower filament temperatures of 1000-1100 °C and short reaction time (t ? 15 min), the free radical chain reaction is equally important as the silene chemistry. With increasing filament temperature and reaction time, silene chemistry predominates. PMID:22934960

Badran, I; Forster, T D; Roesler, R; Shi, Y J

2012-09-12

89

A large atomic chlorine source inferred from mid-continental reactive nitrogen chemistry  

Microsoft Academic Search

Halogen atoms and oxides are highly reactive and can profoundly affect atmospheric composition. Chlorine atoms can decrease the lifetimes of gaseous elemental mercury and hydrocarbons such as the greenhouse gas methane. Chlorine atoms also influence cycles that catalytically destroy or produce tropospheric ozone, a greenhouse gas potentially toxic to plant and animal life. Conversion of inorganic chloride into gaseous chlorine

Joel A. Thornton; James P. Kercher; Theran P. Riedel; Nicholas L. Wagner; Julie Cozic; John S. Holloway; William P. Dubé; Glenn M. Wolfe; Patricia K. Quinn; Ann M. Middlebrook; Becky Alexander; Steven S. Brown

2010-01-01

90

Interaction of gaseous D atoms with CH3I adsorbed on Pt(111), H/Pt(111), and C/Pt(111) surfaces: From hot-atom to Eley-Rideal phenomenology  

NASA Astrophysics Data System (ADS)

The interaction of gaseous D atoms with methyl iodide molecules adsorbed on Pt(111), hydrogen saturated Pt(111), and graphite monolayer covered Pt(111) surfaces was studied. Direct product rate measurements were employed to determine the reaction kinetics. On all substrates, incoming D atoms abstract the methyl group from adsorbed CH3I via gaseous CH3D formation. In the monolayer regime of CH3I/Pt(111) pure hot-atom phenomenology was observed in the rates. With multilayers as targets, the fluence dependence of the rates get Eley-Rideal-type. With a coadsorbed H monolayer present, the CH3D rates at a CH3I monolayer on Pt(111) are affected by the suppression of hot-atom sticking. Accordingly, the rate curves exhibit similar features as expected for Eley-Rideal phenomenology. However, CH4 as a product and simultaneous abstraction of adsorbed H via gaseous HD and H2 formation clearly demonstrate that hot-atom reactions occur. With CH3I adsorbed on a graphite monolayer on Pt(111), the abstraction kinetics of methyl was found to agree with the operation of an Eley-Rideal mechanism. This observation is in line with the expectation that hot atoms do not exist on a C/Pt(111) surface.

Wehner, S.; Küppers, J.

1998-07-01

91

In situ observation of thermomigration of Sn atoms to the hot end of 96.5Sn-3Ag-0.5Cu flip chip solder joints  

NASA Astrophysics Data System (ADS)

In this study, we investigated the phenomenon of thermomigration in 96.5Sn-3Ag-0.5Cu flip chip solder joints at an ambient temperature of 150 °C. We observed mass protrusion on the chip side (hot end), indicating that Sn atoms moved to the hot end, and void formation on the substrate side (cold end). The diffusion markers also moved to the substrate side, in the same direction of the vacancy flux, indicating that the latter played a dominant role during the thermomigration process. The molar heat of transport (Q*) of the Sn atoms was 3.38 kJ/mol.

Ouyang, Fan-Yi; Kao, C.-L.

2011-12-01

92

Giant Dipole Radiation And Evidence Of Isospin Mixing Increase With Atomic Number In Hot Nuclei  

SciTech Connect

We present evidence that the isospin mixing studied in a consistent way in highly excited {sup 32}S, {sup 36}Ar, {sup 44}Ti, and {sup 60}Zn nuclei at similar excitation energies, increases with increasing atomic number of self-conjugate nuclei. The observed increase is similar to that predicted for ground-state nuclei.

Kicinska-Habior, M.; Wojcik-Gront, E. [Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw (Poland); Kowalczyk, M. [Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw (Poland); Heavy Ion Laboratory, Warsaw University, Pasteura 5A, 02-093 Warsaw (Poland); Kisielinski, M. [Heavy Ion Laboratory, Warsaw University, Pasteura 5A, 02-093 Warsaw (Poland); Andrzej Soltan Institute for Nuclear Studies (IPJ), 05-400 Swierk/Otwock (Poland)

2008-05-12

93

REVIEW ARTICLE: Atomic scale study of the chemistry of oxygen, hydrogen and water at SiC surfaces  

NASA Astrophysics Data System (ADS)

Understanding the achievable degree of homogeneity and the effect of surface structure on semiconductor surface chemistry is both academically challenging and of great practical interest to enable fabrication of future generations of devices. In that respect, silicon terminated SiC surfaces such as the cubic 3C-SiC(1 0 0) 3 × 2 and the hexagonal 6H-SiC(0 0 0 1) 3 × 3 are of special interest since they give a unique opportunity to investigate the role of surface morphology on oxygen or hydrogen incorporation into the surface. In contrast to silicon, the subsurface structure plays a major role in the reactivity, leading to unexpected consequences such as the initial oxidation starting several atomic planes below the top surface or the surface metallization by atomic hydrogen.

Amy, Fabrice

2007-10-01

94

GHz Rabi Flopping to Rydberg States in Hot Atomic Vapor Cells  

NASA Astrophysics Data System (ADS)

We report on the observation of Rabi oscillations to a Rydberg state on a time scale below 1 ns in thermal rubidium vapor. We use a bandwidth-limited pulsed excitation and observe up to 6 full Rabi cycles within a pulse duration of ˜4ns. We find good agreement between the experiment and numerical simulations based on a surprisingly simple model. This result shows that fully coherent dynamics with Rydberg states can be achieved even in thermal atomic vapor, thus suggesting small vapor cells as a platform for room-temperature quantum devices. Furthermore, the result implies that previous coherent dynamics in single-atom Rydberg gates can be accelerated by 3 orders of magnitude.

Huber, B.; Baluktsian, T.; Schlagmüller, M.; Kölle, A.; Kübler, H.; Löw, R.; Pfau, T.

2011-12-01

95

Hot atom populations in the terrestrial atmosphere. A comparison of the nonlinear and linearized Boltzmann equations  

NASA Astrophysics Data System (ADS)

We use a finite difference discretization method to solve the space homogeneous, isotropic nonlinear Boltzmann equation. We study the time evolution of the distribution function in relation to the solution of the linearized Boltzmann equation for three different initial conditions. The relaxation process is described in terms of the Laguerre moments and the spectral properties of the linearized collision operator. The motivation is the need to include self-collisions in the study of suprathermal oxygen atoms in the terrestrial exosphere.

Sospedra-Alfonso, Reinel; Shizgal, Bernie D.

2012-11-01

96

Surface chemistry of the atomic layer deposition of metals and group III oxides  

NASA Astrophysics Data System (ADS)

Atomic Layer Deposition (ALD) is a thin-film growth technique offering precise control of film thickness and the ability to coat high-aspect-ratio features such as trenches and nanopowders. Unlike other film growth techniques, ALD does not require harsh processing conditions and is not limited by line-of-sight deposition. Emerging applications for ALD materials include semiconductor devices, gas sensors, and water-diffusion barriers. The chemistry behind ALD involves understanding how the precursors interact with surfaces to deposit the desired material. All ALD precursors need to be stable on the substrate to ensure self-limiting behavior yet reactive enough to be easily removed with the second reagent. Recent precursor development has provided many volatile organometallic compounds for most of the periodic table. As the number of precursors increases, proper precursor choice becomes crucial. This is because the film properties, growth rates, and growth temperature vary widely between the precursors. Many of the above traits can be predicted with knowledge of the precursor reaction mechanisms. This thesis aims to link surface reaction mechanisms to observed growth and nucleation trends in metal and oxide ALD systems. The first portion of this thesis explores the mechanisms of two ALD oxide systems. First, I examine the mechanism of ALD alumina with ozone. Ozone is used as an oxidant in the semiconductor industry because the deposited Al 2O3 films possess better insulating properties and ozone is easier to purge from a vacuum system. FT-IR analysis reveals a complicated array of surface intermediates such as formate, carbonate, and methoxy groups that form during Al2O3 growth with ozone. Next, a new method to deposit thin films of Ga2O3 is introduced. Gallium oxide is a transparent conducting oxide that needs expensive solid precursors to be deposited by ALD. I show that trimethylgallium is a good high-temperature ALD precursor that deposits films of Ga2O 3 with low impurities and a good growth rate. The second section of this thesis focuses on two metal ALD systems. One major drawback of metal ALD systems is their inability to nucleate on many oxide surfaces. This greatly limits the applications of metal ALD for interconnects and flexible electrodes. The first emphasis is an on a new palladium ALD system using palladium (II) hexafluoroacetylaceonate (Pd(hfac)2) and formalin. FT-IR studies show that the Pd(hfac)2 dissociatively adsorbs, releasing free hfacH molecules that bind to Lewis acid sites on the alumina. The observed nucleation period of Pd is linked to surface poisoning by hfacH. In a related experiment, I use trimethylaluminum exposures to remove excess hfacH from the surface. Trimethylaluminum is able to ligand exchange an easier to remove methyl group with the surface hfacH, This treatment causes palladium to nucleate much more rapidly and deposit at lower temperatures. Finally, I examine ToRuS, a new precursor solution for Ru ALD. ToRuS, a solution of RuO4 in perfluoroethers, deposits ruthenium faster and at lower temperatures than all other Ru precursors. The mechanism for deposition and role of the perfluoroethers, however, is poorly understood. In the first study, I couple FT-IR spectroscopy with ab-initio calculations to identify the surface species formed when the perfluoroether solvent adsorbs on alumina. These surface species bind strongly to the alumina surface, creating a nonpolar, fluorinated layer. I then use these results to understand how ToRuS deposits Ru films. The fluorinated layer solvates RuO4, stabilizing it near the surface until it can be reduced by H2 gas. FT-IR and XPS analysis shows that the fluorinated layer does not leave carbonaceous impurities on the ruthenium surface or impedes metal deposition.

Goldstein, David Nathan

97

The Atomic and Molecular Universe: Collisions in Hot Plasmas to the Building Blocks of Life  

NASA Astrophysics Data System (ADS)

Basic atomic and molecular collision phenomena are operative at the core of an enormous range of astrophysical plasmas, including the interstellar medium (ISM), protostellar regions, stars, our Sun, and planetary atmospheres, ionospheres, & magnetospheres. Laboratory measurements of cross sections and lifetimes are needed to establish plasma charge-state distributions. A required database includes absolute electron- impact excitation, ionization, and recombination cross sections in highly-charged ions (HCIs); photoionization cross sections; and absolute single- and multiple charge-exchange cross sections between a neutral target and an HCI, as when a solar/stellar wind meets a circumstellar cloud or passing comet to generate X- rays via charge exchange. Since satellites and spacecraft often detect photons from the astronomical object, the infrared-to-X- ray emissions are governed by a balance between collisional excitation and radiative decay, so that accurate lifetimes, branching fractions, and Einstein A and B coefficients are also needed. On yet another level, observations in the infrared-to- millimeter wave region from, for example, the Green Bank Telescope, Spitzer, Sofia, Herschel, and the James Webb Telescope provide information on molecular formation in the ISM and protostellar regions. Over 144 atomic, molecular, and ionic species have been identified to date. Recent laboratory results will be given on formation of some of these polyatomic molecules in superthermal, ground-state H- and O-atom collisions with simple, grain-adsorbed species, and results compared to the impressive array of space spectroscopic data.

Chutjian, Ara

2010-03-01

98

Effects of quantum chemistry models for bound electrons on positron annihilation spectra for atoms and small molecules  

NASA Astrophysics Data System (ADS)

The Doppler-shift spectra of the ?-rays from positron annihilation in molecules were determined by using the momentum distribution of the annihilation electron-positron pair. The effect of the positron wavefunction on spectra was analysed in a recent paper (Green et al 2012 New J. Phys. 14 035021). In this companion paper, we focus on the dominant contribution to the spectra, which arises from the momenta of the bound electrons. In particular, we use computational quantum chemistry models (Hartree-Fock with two basis sets and density functional theory (DFT)) to calculate the wavefunctions of the bound electrons. Numerical results are presented for noble gases and small molecules such as H2, N2, O2, CH4 and CF4. The calculations reveal relatively small effects on the Doppler-shift spectra from the level of inclusion of electron correlation energy in the models. For atoms, the difference in the full-width at half-maximum of the spectra obtained using the Hartree-Fock and DFT models does not exceed 2%. For molecules the difference can be much larger, reaching 8% for some molecular orbitals. These results indicate that the predicted positron annihilation spectra for molecules are generally more sensitive to inclusion of electron correlation energies in the quantum chemistry model than the spectra for atoms are.

Wang, Feng; Ma, Xiaoguang; Selvam, Lalitha; Gribakin, Gleb; Surko, Clifford M.

2012-08-01

99

Bonds Between Metal Atoms: A New Mode of Transition Metal Chemistry.  

ERIC Educational Resources Information Center

|Discusses polynuclear metal clusters (containing two or more metal atoms bonded to one another as well as to nonmetallic elements), including their formation and applications. Studies of bonds between metal atoms reveal superconductors, organic-reaction catalysts, and photosensitive complexes that may play a role in solar energy. (JN)|

Cotton, F. Albert; Chisholm, Malcolm H.

1982-01-01

100

Comments on ''Introduction to the chemistry of fractionally charged atoms: Electronegativity''  

Microsoft Academic Search

A comparison is made between the electronegativities of ''quark atoms'' as predicted by a recent article, and those suggested by traditional chemical methods. It is shown that the neglect of valence-state considerations for the ionization energies and electron affinities produces serious errors in calculating electronegativities by the Mulliken method. As analyses of the values for ''normal atoms'' show such disparities,

Joel Liebman; James Huheey

1987-01-01

101

Comments on ``Introduction to the chemistry of fractionally charged atoms: Electronegativity''  

Microsoft Academic Search

A comparison is made between the electronegativities of ``quark atoms'' as predicted by a recent article, and those suggested by traditional chemical methods. It is shown that the neglect of valence-state considerations for the ionization energies and electron affinities produces serious errors in calculating electronegativities by the Mulliken method. As analyses of the values for ``normal atoms'' show such disparities,

Joel F. Liebman; James E. Huheey

1987-01-01

102

Chemistry of the heaviest elements--one atom at a time  

Microsoft Academic Search

In keeping with the goal of the Viewpoint series of the Journal of Chemical Education, this article gives a 75-year perspective of the chemistry of the heaviest elements, including a 50-year retrospective view of past developments, a summary of current research achievements and applications, and some predictions about exciting, new developments that might be envisioned within the next 25 years.

Darleane C. Hoffman; Diana M. Lee

2000-01-01

103

Determination of Mercury in Milk by Cold Vapor Atomic Fluorescence: A Green Analytical Chemistry Laboratory Experiment  

ERIC Educational Resources Information Center

|Green analytical chemistry principles were introduced to undergraduate students in a laboratory experiment focused on determining the mercury concentration in cow and goat milk. In addition to traditional goals, such as accuracy, precision, sensitivity, and limits of detection in method selection and development, attention was paid to the…

Armenta, Sergio; de la Guardia, Miguel

2011-01-01

104

Determination of Mercury in Milk by Cold Vapor Atomic Fluorescence: A Green Analytical Chemistry Laboratory Experiment  

ERIC Educational Resources Information Center

Green analytical chemistry principles were introduced to undergraduate students in a laboratory experiment focused on determining the mercury concentration in cow and goat milk. In addition to traditional goals, such as accuracy, precision, sensitivity, and limits of detection in method selection and development, attention was paid to the…

Armenta, Sergio; de la Guardia, Miguel

2011-01-01

105

Photon pair production from a hot atomic ensemble in the diamond configuration  

NASA Astrophysics Data System (ADS)

This thesis discusses four-wave mixing (4WM) in a warm ensemble of rubidium using the diamond configuration level structure. Both classical 4WM and nonclassical photon-pair production are investigated. Quantum information science has spawned a great amount of experimental work on the interaction of light with collective modes of excitation in atomic ensembles. Plans to build quantum networks and quantum repeaters with atom ensembles take advantage of nonlinear interactions to produce and store non-classical states of light. These technologies will require photon sources that not only generate nonclassical light, but also resonant, narrow band light. Here we investigate a system which could be used as such a source. We take advantage of the 4WM interaction in a warm ensemble of Rubidium atoms. Our scheme utilizes the diamond energy level configuration which, in rubidium, allows for correlated pairs at telecommunications wavelengths. We start by examining the properties of classical 4WM in the system. We measure the resonance structure and see that it can be understood in terms of velocity class selective resonant enhancement and power splitting effects. The efficiency of the process is low and limited by linear absorption of the pumps. Our observations agree with a semi-classical Maxwell-Bloch theoretical treatment. Next we observe pair generation by spontaneous 4WM from the warm ensemble. The temporal profile of the cross-correlation function (CCF) for the photons depends on pump-laser power and detuning. This allows us to produce biphotons with controllable spectra. A simple quantum optical theoretical treatment based on linear filtering gives qualitative agreement with the data. We show that the photon pairs are polarization entangled, clearly violating Bell's Inequality. A perturbative quantum optical treatment predicts the polarization state of the pairs and agrees with our measurements. We analyze the photon statistics of the source and find the largest violation of the two beam Cauchy-Schwarz inequality from a warm atomic source yet. We cast the system as a heralded single photon source at telecommunications wavelengths and see that it is competitive with other systems in terms of spectral brightness.

Willis, Richard Thomas

106

From {sup 3}He{at}C{sub 60} to {sup 3}H{at}C{sub 60}: Hot-atom incorporation of tritium in C{sub 60}  

SciTech Connect

The introduction of tritium into the cavity of C{sub 60} using hot-atom chemistry was studied. Neutron irradiation of {sup 3}He in {sup 3}He{at}C{sub 60} produced tritium ions and atoms which enter the C{sub 60}. {sup 3}H{at}C{sub 60} was detected with a scintillation counter. The Bingel reaction was carried out on this material under conditions so that the monoadduct formed predominantly, and the products were probed for tritium activity. Analysis with {sup 3}He NMR gave a peak with the characteristic {sup 3}He shift for the malonate product. The product fractions gave only 33% of the original activity; most was recovered in the unreacted C{sub 60} portion. No reaction was observed between C{sub 60} and the stable radical di-tert-butylnitroxide; all tritium activity was recovered in the C{sub 60} peak. These results suggest similarities in properties between {sup 3}H{at}C{sub 60} and pure C{sub 60}, implying that the tritium exists as a free atom inside the molecule.

Khong, A.; Cross, R.J.; Saunders, M.

2000-05-04

107

Application of Fluid-Chemistry Studies to a Hot-Dry-Rock Geothermal System: I. Neutron-Activation Studies.  

National Technical Information Service (NTIS)

Neutron activation analysis methods were developed for determination of element concentrations in geothermal system waters, bulk rock samples, separated mineral phases, and intergranular salts from a hot dry rock geothermal system. Selected trace and majo...

R. Vidale I. Binder A. Gancarz

1981-01-01

108

Effect of Si-H bond on the gas-phase chemistry of trimethylsilane in the hot wire chemical vapor deposition process.  

PubMed

The effect of the Si-H bond on the gas-phase reaction chemistry of trimethylsilane in the hot-wire chemical vapor deposition (HWCVD) process has been studied by examining its decomposition on a hot tungsten filament and the secondary gas-phase reactions in a reactor using a soft laser ionization source coupled with mass spectrometry. Trimethylsilane decomposes on the hot filament via Si-H and Si-CH(3) bond cleavages. A short-chain mechanism is found to dominate in the secondary reactions in the reactor. It has been shown that the hydrogen abstractions of both Si-H and C-H occur simultaneously, with the abstraction of Si-H being favored. Tetramethylsilane and hexamethyldisilane are the two major products formed from the radical recombination reactions in the termination steps. Three methyl-substituted disilacyclobutane molecules, i.e., 1,3-dimethyl-1,3-disilacyclobutane, 1,1,3-trimethyl-1,3-disilacyclobutane, and 1,1,3,3-tetramethyl-1,3-disilacyclobutane are also produced in reactor from the cycloaddition reactions of methyl-substituted silene species. Compared to tetramethylsilane and hexamethyldisilane, a common feature with trimethylsilane is that the short-chain mechanism still dominates. However, a more active involvement of the reactive silene intermediates has been found with trimethylsilane. PMID:21834557

Shi, Y J; Li, X M; Toukabri, R; Tong, L

2011-08-25

109

Site-specific bimolecular chemistry: the reactivity of Cl atoms and butanes  

NASA Astrophysics Data System (ADS)

The reaction of chlorine atoms with selectively-deuterated butanes to form HCl and/or DCl under single-collision conditions has been studied. Photolysis of Cl2 with 351 or 308 nm light produces Cl atoms that subsequently abstract an H or D atom to form the corresponding hydrogen chloride product. HCl and DCl are detected via 2 plus 1 multiphoton ionization. For both n-butane and isobutane when viewed on a per hydrogen atom basis, the 'middle' site is preferred. When viewed on a per carbon site basis, this propensity is still observed in n- butane, but isobutane shows no dominant site specificity. Mechanistically, the data can be interpreted qualitatively in several ways, but currently the most convincing argument suggests that a direct, impulsive encounter is involved.

Cowen, Kenneth A.; Yen, Yu-Fong; Lorenz, K. Thomas; Koplitz, Brent D.

1995-09-01

110

Comments on ''Introduction to the chemistry of fractionally charged atoms: Electronegativity''  

SciTech Connect

A comparison is made between the electronegativities of ''quark atoms'' as predicted by a recent article, and those suggested by traditional chemical methods. It is shown that the neglect of valence-state considerations for the ionization energies and electron affinities produces serious errors in calculating electronegativities by the Mulliken method. As analyses of the values for ''normal atoms'' show such disparities, it is likely that the new numbers are in error.

Liebman, J.F.; Huheey, J.E.

1987-09-01

111

Hydrocarbon measurements during tropospheric ozone depletion events: Evidence for halogen atom chemistry  

Microsoft Academic Search

During the Arctic Tropospheric Ozone Chemistry 1996 (ARCTOC 96) field campaign (March 29 to May 15, 1996), in situ measurements of C2-C8 hydrocarbons, selected C1-C2 halocarbons, and carbon monoxide were carried out at Ny Ålesund, Svalbard (78°55'N,11°56'E). Two major tropospheric ozone depletions were observed during this period. In each case, concurrent depletion of alkanes and ethyne but no significant changes

B. Ramacher; J. Rudolph; R. Koppmann

1999-01-01

112

Interaction of gaseous D atoms with alkyl halides adsorbed on Pt(111), H/Pt(111), and C/Pt(111) surfaces: Hot-atom and Eley-Rideal reactions. I. Methyl bromide  

NASA Astrophysics Data System (ADS)

The interaction of gaseous D atoms with methyl bromide molecules adsorbed on Pt(111), hydrogen saturated Pt(111), and graphite monolayer covered Pt(111) surfaces was studied in order to elucidate the reaction mechanisms. The reaction kinetics at 85 K surface temperature were measured as a function of the methyl bromide precoverage by monitoring reaction products simultaneously with D atom exposure. On all substrates incoming atoms abstract the methyl group from adsorbed CH3Br via gaseous CH3D formation. In the monolayer regime of CH3Br/Pt(111) pure hot-atom phenomenology was observed in the rates. At multilayer targets the fluence dependence of the kinetics gets Eley-Rideal-like. With coadsorbed H present, the reaction of D with adsorbed methyl bromide revealed in addition to CH3D a CH4 product. This and simultaneous abstraction of adsorbed H via gaseous HD and H2 products clearly demonstrates that hot-atom reactions occur. At CH3Br adsorbed on a graphite monolayer on Pt(111) the abstraction kinetics of methyl was found to agree with the operation of an Eley-Rideal mechanism. These observations are in line with the expectation that hot-atoms do not exist on a C/Pt(111) surface but on Pt(111) and H/Pt(111) surfaces. The methyl abstraction cross-sections in the monolayer regime of methyl bromide were determined as about 0.25 Å2, irrespective of the nature of the substrate. This value is in accordance with direct, Eley-Rideal or hot-atom reactions.

Wehner, S.; Küppers, J.

1999-08-01

113

Atomic scale structure and chemistry of interfaces by Z-contrast imaging and electron energy loss spectroscopy in the STEM  

SciTech Connect

The macroscopic properties of many materials are controlled by the structure and chemistry at the grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. The high-resolution Z-contrast imaging technique in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition can be interpreted intuitively. This direct image allows the electron probe to be positioned over individual atomic columns for parallel detection electron energy loss spectroscopy (PEELS) at a spatial resolution approaching 0.22nm. The bonding information which can be obtained from the fine structure within the PEELS edges can then be used in conjunction with the Z-contrast images to determine the structure at the grain boundary. In this paper we present 3 examples of correlations between the structural, chemical and electronic properties at materials interfaces in metal-semiconductor systems, superconducting and ferroelectric materials.

McGibbon, M.M.; Browning, N.D.; Chisholm, M.F.; Pennycook, S.J.

1993-12-01

114

Deep Atomic Binding (DAB) Hypothesis: A New Approach of Fission Product Chemistry  

SciTech Connect

Former studies assumed that, after fission process occurs, the highly ionized new born atoms (20-22 positive charge), ionize the media in which they pass through before becoming stable atoms in a manner similar to 4-MeV ?-particles. Via ordinary chemical reactions with the surroundings, each stable atom has a probability to form chemical compound. Since there are about 35 different elemental atoms created through fission processes, a large number of chemical species were suggested to be formed. But, these suggested chemical species were not found in the environment after actual releases of FP during accidents like TMI (USA, 1979), and Chernobyl (former USSR, 1986), also the models based on these suggested reactions and species could not interpret the behavior of these actual species. It is assumed here that the ionization states of the new born atoms and the long term high temperature were not dealt with in an appropriate way and they were the reasons of former models failure. Our new approach of Deep Atomic Binding (DAB) based on the following: 1-The new born atoms which are highly ionized, 10-12 electrons associated with each nucleus, having a large probability to create bonds between them to form molecules. These bonds are at the L, or M shells, and we call it DAB. 2-The molecules stay in the reactor at high temperatures for long periods, so they undergo many stages of composition and decomposition to form giant molecules. By applying DAB approach, field data from Chernobyl, TMI and nuclear detonations could be interpreted with a wide coincidence resulted. (author)

Ajlouni, Abdul-Wali M.S. [Ministry of Energy and Mineral Resources (Jordan)

2006-07-01

115

High energy halogen atom reactions activated by nuclear transformations: Performance report for period February 15, 1984 to October 31, 1986  

SciTech Connect

The following were studied in the investigation of stereochemistry and mechanisms of halogen atom reactions with chiral molecules: mass effects in bimolecular hot homolytic substitution reactions, bimolecular homolytic substitution reactions of thermal fluorine atoms, and high-energy chlorine-for-chlorine substitution in liquid enantiomers. Applications of hot-atom chemistry were made to trace element and molecular activation analysis and to solute-solute interactions of aqueous solutions of nucleosides and bases. (DLC)

Rack, E.P.

1986-10-01

116

Shippingport Atomic Power Station Steam Generator Tube Damage and Water Chemistry Control (1965--1975).  

National Technical Information Service (NTIS)

The four stainless steel tubed steam generators in the Shippingport Atomic Power Station were replaced in 1964 with larger, horizontal, NiCrFe Alloy 600 tubed units consistent with a power uprating of the plant. Each of the four Alloy 600 tubed units expe...

W. J. Singley

1978-01-01

117

Shippingport Atomic Power Station steam generator tube damage and water chemistry control (1965--1975)  

Microsoft Academic Search

The four stainless steel tubed steam generators in the Shippingport Atomic Power Station were replaced in 1964 with larger, horizontal, NiCrFe Alloy 600 tubed units consistent with a power uprating of the plant. Each of the four Alloy 600 tubed units experienced tube leakage attributed to corrosion by water treatment chemicals (sodium phosphates) which concentrated locally on the tubes in

Singley

1978-01-01

118

Rhenium chemistry of azooximes: oxygen atom transfer, azoimine chelation, and imine-oxime contrast.  

PubMed

The concerned azooximes (L1OH, 1) are of type p-X-C6H4C(N2Ph)(NOH) (X = H, Me, Cl). The reaction of [Re(MeCN)Cl3(PPh3)2] with [Ag(L1OH)(L1O)] in cold dichloromethane-acetonitrile solvent has furnished the green colored ionized azoimine complex [ReV(O)Cl(PPh3)2(L1)](PF6), 2. In effect L1O- has undergone oxidative addition, the oxygen atom being transferred to the metal site. Upon treatment of [ReV(NPh)Cl3(PPh3)2] with L1OH in solution, the neutral azoimine complex [ReV(NPh)Cl3(L1H)], 3, resulted due to the spontaneous transfer of the oxime oxygen atom to a PPh3 ligand, which is eliminated as OPPh3. In contrast, the oxime of 2-acetylpyridine (L2OH, 4) did not undergo oxygen atom transfer and simply afforded the imine-oxime complex [ReV(NC6H4Y)Cl2(PPh3)(L2O)], 5, upon reacting with [ReV(NC6H4Y)Cl3(PPh3)2] (Y = H, Me, Cl). The spectral and electrochemical properties of 2, 3, and 5 and the structures of three representative compounds are reported. In the cation of 2 (X = H) the two PPh3 ligands lie trans to each other and the equatorial plane is defined by the five-membered azoimine chelate ring and the oxo and chloro ligands. The oxo ligand which forms a model triple bond (Re-O length 1.616(6) A) lies cis to the imine-N atom. In 3 (X = Cl) the ReCl3 fragment has meridional geometry and the imido nitrogen lies trans to the imine nitrogen of the planar azoimine chelate ring. In 5 x H2O (Y = Me), the Cl, oximato-N, and P atoms define an equatorial plane and the pyridine-N lies trans to the imido-N. The water of crystallization is hydrogen bonded to the oximato oxygen atom (O...O, 2.829(5) A). Reaction models in which chelation of the azooxime precedes oxygen atom transfer are proposed on the basis of oxophilicity of trivalent rhenium, Lewis acid activity of pentavalent rhenium, electron withdrawal by the azo group, and observed relative disposition of ligands in products. PMID:15859286

Chakraborty, Indranil; Panda, Bikash Kumar; Gangopadhyay, Jaydip; Chakravorty, Animesh

2005-02-21

119

KfK, Institut fuer Heisse Chemie. Ergebnisbericht ueber Forschungs- und Entwicklungsarbeiten 1991. (Progress report on research and development work 1991 of the Department of Hot Chemistry, Karlsruhe Nuclear Research Center).  

National Technical Information Service (NTIS)

In the year under review, the Institute of Hot Chemistry (IHCH) was in the midst of a thematic reorientation process. The priority of future chemical-technical work will be in the field of the development of supercriticality processes. The objective of su...

1991-01-01

120

Atomic physics research at Columbia University Chemistry Department. Progress report, April 1, 1982-March 31, 1983  

SciTech Connect

During the last year we: (1) measured the rotational and vibrational distribution of the S/sub 2/ produce of the spin conserving reaction: S(/sup 1/D) + OCS ..-->.. S/sub 2/ (a/sup 1/..delta..) + CO; (2) developed a two photon laser induced fluorescence method for the time resolved detection of carbon atoms in both their ground /sup 3/P and metastable /sup 1/D states; (3) showed that the reaction F + HI ..-->.. HF + I produces I atoms only in the /sup 2/P/sub 3/2/ state; (4) observed for the first time in the gas phase the Walden inversion: F + CH/sub 3/I ..-->.. CH/sub 3/F + I, with both J=3/2 and J=1/2 atoms being produced in a 2/1 ratio; (5) showed by laser induced fluorescence that the IF product of the reaction: F + RI ..-->.. R + IF (R = CH/sub 3/,C(CH/sub 3/)/sub 3/,CF/sub 3/) is vibrationally and rotationally cold.

Not Available

1983-01-01

121

Atomic Processes of Hot Ultra-Dense Plasmas Technical Progress Report for FY01 National Laser User Facility Grant  

SciTech Connect

The experimental and theoretical activities of our FY01 NLUF work have been largely successful, and we are on track for completing our proposed two year investigation of the atomic physics of hot, ultra-dense plasmas by the end of FY02. The experimental activities were two half days of shots (2/21/01, and 8/2/01). All of the time-resolved x-ray spectroscopic data from the February shots have been reduced and analyzed. Four shots using the 1ns square pulse shape SG1014 were complete successes, reproducibly achieving peak electron densities at or above 2x10{sup 24}/cc. The results from the February experiments clearly demonstrate large plasma-induced line shifts. To achieve higher densities, the August shots concentrated on the use of the shaped pulse, RM1107, and reduced fill pressures. In order to probe the ultra high densities that occur near stagnation, , clear spectroscopic signals of the Ar K-shell lines must be observed. In the February shots, Ar lines were not observed through stagnation due to the low core electron temperatures caused by the enhanced radiative cooling of the Ar. Higher densities were most likely achieved in these shots; however the diagnostic lines were not present. With the lower Ar dopant level in the August shots, the Ar lines were observed throughout the implosion. We believe the ultra-high density portions of these shots were observed. Though the August spectral data are still being digitized, the raw data appear promising. The theoretical activities include the development of a fully non-linear semi-classical electron broadening theory for the Ar Ly-b through -d lines, and the automation of the data fitting procedure using a highly optimized least-squares minimization.

C. F. Hooper, Jr. D. A. Haynes, Jr.

2001-08-13

122

Calculation of the Relative Chemical Stabilities of Proteins as a Function of Temperature and Redox Chemistry in a Hot Spring  

PubMed Central

Uncovering the chemical and physical links between natural environments and microbial communities is becoming increasingly amenable owing to geochemical observations and metagenomic sequencing. At the hot spring known as Bison Pool in Yellowstone National Park, the cooling of the water in the outflow channel is associated with an increase in oxidation potential estimated from multiple field-based measurements. Representative groups of proteins whose sequences were derived from metagenomic data also exhibit an increase in average oxidation state of carbon in the protein molecules with distance from the hot-spring source. The energetic requirements of reactions to form selected proteins used in the model were computed using amino-acid group additivity for the standard molal thermodynamic properties of the proteins, and the relative chemical stabilities of the proteins were investigated by varying temperature, pH and oxidation state, expressed as activity of dissolved hydrogen. The relative stabilities of the proteins were found to track the locations of the sampling sites when the calculations included a function for hydrogen activity that increases with temperature and is higher, or more reducing, than values consistent with measurements of dissolved oxygen, sulfide and oxidation-reduction potential in the field. These findings imply that spatial patterns in the amino acid compositions of proteins can be linked, through energetics of overall chemical reactions representing the formation of the proteins, to the environmental conditions at this hot spring, even if microbial cells maintain considerably different internal conditions. Further applications of the thermodynamic calculations are possible for other natural microbial ecosystems.

Dick, Jeffrey M.; Shock, Everett L.

2011-01-01

123

Interstellar chemistry of atomic nitrogen: low temperature kinetics of the N + OH and N + NO reactions.  

NASA Astrophysics Data System (ADS)

In dense interstellar clouds, where temperatures fall as low as 10 K, N-bearing species are found to stay in the gas-phase. Consequently, these molecules are used to define the prevailing physical conditions. N-bearing oxygenated species, such as nitric oxide NO are used to indirectly trace the depletion of O-bearing species such as OH and H_2O, which are not observable in these regions. Thus reactions (1) and (2) play an important role in the destruction of NO and the formation of molecular nitrogen from atomic nitrogen. They also thought to play a role in the Martian and Venusian atmospheres. However, the extrapolations of reactive rate coefficients measured at high temperatures to low temperatures are often unreliable since many exothermic neutral-neutral reactions exhibit non-Arrhenius behaviour at such low temperatures. (1) N + NO ? N_2 + O and (2) N + OH ? NO + H. We will present measurements using the CRESU technique over the range 50 - 300 K, coupling microwave discharge methods for the production of atomic nitrogen to resonance fluorescence or pulsed laser photolysis / laser induced fluorescence techniques. We have found that reaction (1) exhibits a small negative temperature dependence in the range 50 - 300 K which diverges from the expressions used in the astrochemical databases UMIST-06 and OSU-08. The only experimental investigation of reaction (2) to date at low temperature 103 - 294 K was performed by Smith et al.: the rate coefficients are seen to increase as the temperature decreases. The most recent theoretical study by Jorfi et al. [6] predicted lower rate coefficients and a maximum value at 80 K. New experimental results will be presented to elucidate the behavior of this reaction at low temperatures. In combination with the lastest published calculations, new recommendations for the temperature dependence of the two reaction rates will be given and the effect on astrochemical models of different media will be presented.

Bergeat, A.; Daranlot, J.; Hickson, K. M.

2011-05-01

124

Atomic force microscopy imaging and probing of DNA, proteins, and protein DNA complexes: silatrane surface chemistry.  

PubMed

Despite their rather recent invention, atomic force microscopes are widely available commercially. AFM and its special modifications (tapping mode and noncontact operation in solution) have been successfully used for topographic studies of a large number of biological objects including DNA, RNA, proteins, cell membranes, and even whole cells. AFM was also successfully applied to studies of nucleic acids and various protein DNA complexes. Part of this success is due to the development of reliable sample preparation procedures. This chapter describes one of the approaches based on chemical functionalization of mica surface with 1-(3-aminopropyl) silatrane (APS). One of the most important properties of APS-mica approach is that the sample can be deposited on the surface in a wide range of ionic strengths, in the absence of divalent cations and a broad range of pH. In addition to imaging of dried sample, APS-mica allows reliable and reproducible time lapse imaging in aqueous solutions. Finally, APS mica is terminated with reactive amino groups that can be used for covalent and ionic attachment of molecules for AFM force spectroscopy studies. The protocols for the preparation of APS, functionalization with APS mica and AFM probes, preparation of samples for imaging in air and in aqueous solutions, and force spectroscopy studies are outlined. All these applications are illustrated with a few examples. PMID:19378175

Lyubchenko, Yuri L; Shlyakhtenko, Luda S; Gall, Alexander A

2009-01-01

125

Hot Canyon  

ScienceCinema

This historical film footage, originally produced in the early 1950s as part of a series by WOI-TV, shows atomic research at Ames Laboratory. The work was conducted in a special area of the Laboratory known as the "Hot Canyon."

126

The effects of solution chemistry on the sticking efficiencies of viable Enterococcus faecalis: An atomic force microscopy and modeling study  

NASA Astrophysics Data System (ADS)

Atomic force microscopy (AFM) and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory in combination with the interaction force boundary layer (IFBL) model have been used to empirically and theoretically calculate sticking efficiencies (?) of Enterococcus faecalis cells against a silica glass surface. Sticking efficiencies were calculated in solutions of varying pH and ionic strength and related to maximum distances of transport through a hypothetical soil block using colloid filtration theory. AFM measurements show that the repulsive and attractive forces between E. faecalis cells and a glass surface are a function of ionic strength but are less sensitive to changes in solution pH. Zeta (?)-potential measurements of the cells and glass surfaces correlate with these trends. Calculated DLVO energy profiles predict much greater sensitivity to changing solution chemistry. Sticking efficiencies derived from AFM measurements range from 9.6 × 10 -17 to 1 in solutions of low ionic strength (IS) and from 2.6 × 10 -33 to 1 at higher IS. Corresponding ? values determined from DLVO theory are essentially zero in all tested solutions. Sticking efficiencies calculated in this study are smaller than values determined from column and field studies in similar systems; however, ? derived from AFM data and the IFBL model more closely represent field data than do values calculated from DLVO energy values. A comparison with different methods of calculating ? suggests that reversible adhesion may be significant in column-scale transport studies.

Cail, Tracy L.; Hochella, Michael F.

2005-06-01

127

Reduction biodegradable brushed PDMAEMA derivatives synthesized by atom transfer radical polymerization and click chemistry for gene delivery.  

PubMed

Novel reducible and degradable brushed poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) derivatives were synthesized and evaluated as non-viral gene delivery vectors. First, alkyne-functionalized poly(aspartic acid) with a disulfide linker between the propargyl group and backbone poly([(propargyl carbamate)-cystamine]-?,?-aspartamide) (P(Asp-SS-AL)) was synthesized. Second, linear low molecular weight (LMW) monoazido-functionalized PDMAEMAs synthesized via atom transfer radical polymerization were conjugated to the polypeptide side-chains of P(Asp-SS-AL) via click chemistry to yield high molecular weight (HMW) polyaspartamide-based disulfide-containing brushed PDMAEMAs (PAPDEs). The PAPDEs were able to condense plasmid DNA to form 100 to 200nm polyplexes with positive ?-potentials. Moreover, in the presence of dithiothreitol the PAPDEs degraded into LMW PDAMEMA, resulting in disintegration of the PAPDE/DNA polyplexes and subsequent release of plasmid DNA. In vitro experiments revealed that the PAPDEs were less cytotoxic and more effective in gene transfection than control 25kDa poly(ethyleneimine) and HMW linear PDMAEMA. In conclusion, reducible and degradable polycations composed of LMW PDMAEMAs coupled to a polypeptide backbone via reduction-sensitive disulfide bonds are effective gene vectors with an excellent cytocompatibility. PMID:23660547

Liu, Jia; Xu, Yanglin; Yang, Qizhi; Li, Cao; Hennink, Wim E; Zhuo, Renxi; Jiang, Xulin

2013-05-07

128

Probing the oxidation chemistry of half-sandwich iridium complexes with oxygen atom transfer reagents.  

PubMed

The new complexes [Ir(Cp*)(phpy)3,5-bis(trifluoromethyl)benzonitrile](+) (1-NCAr(+)) and [Ir(Cp*)(phpy)(styrene)](+) (1-Sty(+), Cp* = ?(5)-pentamethylcyclopentadienyl, phpy = 2-phenylene-?C(1')-pyridine-?N) were prepared as analogues of reported iridium water oxidation catalysts, to study their reactions with oxygen atom transfer (OAT) reagents at low temperatures. In no case was the desired product, an Ir(V)oxo complex, observed by spectroscopy. Instead, ligand oxidation was implicated. Oxidation of 1-NCAr(+) with the OAT reagent dimethyldioxirane (DMDO) yielded dioxygen when analyzed by GC, but formation of a heterogeneous or paramagnetic species was simultaneously observed. This amplifies uncertainty over the actual identity of iridium catalysts in the harsh oxidizing conditions required for water oxidation. Catalyst stability was then assessed for a reported styrene epoxidation mediated by [Ir(Cp*)(phpy)(OH2)](+) (1-OH2(+)). It was found that the OAT reagent iodosobenzene (PhIO) extensively oxidized the organic ligands of 1-OH2(+). Acetic acid was detected as a decomposition product. In addition, both the molecular structure and the aqueous electrochemistry of 1-OH2(+) are described for the first time. Oxidative scans revealed rapid decomposition of the complex. All of the above experiments indicate that degradation of the organic ligands in catalysts built with the Ir(Cp*)(phpy) framework are facile under oxidizing conditions. In separate experiments designed to promote ligand substitution, an unexpected silver-bridged, dinuclear Ir(III) species with terminal hydrides, [{Ir(Cp*)(phpy)H}2Ag](+) (2), was discovered. The source of Ag(+) for complex 2 was identified as AgCl. PMID:24063760

Turlington, Christopher R; Harrison, Daniel P; White, Peter S; Brookhart, Maurice; Templeton, Joseph L

2013-09-24

129

Chemistry of Americium.  

National Technical Information Service (NTIS)

Essential features of the descriptive chemistry of americium are reviewed. Chapter titles are: discovery, atomic and nuclear properties, collateral reading, production and uses, chemistry in aqueous solution, metal, alloys, and compounds, and, recovery, s...

W. W. Schulz

1976-01-01

130

New precursors and chemistry for the growth of transition metal films by atomic layer deposition  

NASA Astrophysics Data System (ADS)

The advancing complexity of advanced microelectronic devices is placing rigorous demands on currently used PVD and CVD deposition techniques. The ALD deposition method is proposed to meet the film thickness and conformality constraints needed by the semiconductor industry in future manufacturing processes. Unfortunately, there is a limited number of chemical precursors available that have high thermal stability, reactivity, and vapor pressure suitable for ALD film growth to occur. These properties collectively contribute to the lack of suitable transition metal precursors available for use in ALD. In this thesis, we report the discovery of a series of novel transition metal diazadienate precursors that promising properties deemed suitable for ALD. The volatility and thermal stability of the new transition metal diazadienyl compounds were studied by preparative sublimation and capillary tube melting point/decomposition experiments. Thermogravimetric analyses (TGA) demonstrate precursor residues of less than 4% at 500 °C. In addition, sublimation data, melting points, and decomposition temperatures for all complexes are presented. The manganese diazadienyl complex has the highest decomposition temperature of the series of complexes produced (325 °C). During preparative sublimations, the product recoveries of all transition metal diazadienyl complexes were greater than 92.0% with nonvolatile residues of less than 7.0%. This is an excellent indication that these complexes may be suitable candidates as metal precursors for ALD. Nickel nitride (NixN) films have been studied as an intermediate material for the formation of both nickel metal and nickel silicide using chemical vapor deposition. Herein, we describe the ALD growth of nickel nitride thin films from bis(1,4-di-tert-butyl-1,3-diazabutadiene) nickel(II) (Ni(tBu2DAD)2) and 1,1-dimethylhydrazine. An ALD window for the deposition of nickel nitride films on 500 nm thermal SiO2 substrates was observed between 225 and 240 °C with a constant growth rate of 0.70 Å/cycle. X-Ray photoelectron spectroscopy (XPS) showed all expected ionizations with carbon concentrations below the detection limit after argon ion sputtering. Due to preferential nitrogen sputtering in XPS, Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA) were performed and subsequently revealed Ni:N ratios between 2-4 for films deposited within the ALD window. AFM measurements revealed a RMS roughness value of 10.8 nm on an as-deposited film at 225°C. All as-deposited films were amorphous as determined by X-ray diffraction. Copper is the primary interconnect material in microelectronics devices, due to its high conductivity and low affinity towards electromigration. With transistor gate lengths scheduled to reach 14 nm by 2014, there are severe demands upon the current film growth techniques used in device fabrication. The ALD film growth method is ideally suited for future microelectronics manufacturing, since it inherently provides highly conformal thin films, even in high aspect ratio nanoscale features, and allows sub-nanometer control over film thicknesses. In Chapter 4, we describe the atomic layer deposition of high purity, low resistivity copper metal thin films using a three precursor sequence entailing Cu(dmap)2, formic acid, and hydrazine. In this process, Cu(dmap) 2 is unreactive towards hydrazine but is transformed to copper(II) formate, which is then readily reduced to copper metal by subsequent hydrazine exposure. The present work therefore addresses a central problem with the ALD growth of metal thin films: low reactivity of metal precursors toward common reducing agents. A constant growth rate of 0.47-0.50 Å/cycle upon prime grade Si(100) was observed at substrate temperatures between 100 and 170 °C. Compositional analyses (XPS and TOF-ERDA) revealed copper films with low levels of carbon, oxygen, nitrogen, and hydrogen. Powder X-ray diffraction spectra of all films showed polycrystalline copper. The resistivities of films grown between 100 and 140 °C ranged b

Knisley, Thomas Joseph

131

KFC2: a knowledge-based hot spot prediction method based on interface solvation, atomic density, and plasticity features.  

PubMed

Hot spots constitute a small fraction of protein-protein interface residues, yet they account for a large fraction of the binding affinity. Based on our previous method (KFC), we present two new methods (KFC2a and KFC2b) that outperform other methods at hot spot prediction. A number of improvements were made in developing these new methods. First, we created a training data set that contained a similar number of hot spot and non-hot spot residues. In addition, we generated 47 different features, and different numbers of features were used to train the models to avoid over-fitting. Finally, two feature combinations were selected: One (used in KFC2a) is composed of eight features that are mainly related to solvent accessible surface area and local plasticity; the other (KFC2b) is composed of seven features, only two of which are identical to those used in KFC2a. The two models were built using support vector machines (SVM). The two KFC2 models were then tested on a mixed independent test set, and compared with other methods such as Robetta, FOLDEF, HotPoint, MINERVA, and KFC. KFC2a showed the highest predictive accuracy for hot spot residues (True Positive Rate: TPR = 0.85); however, the false positive rate was somewhat higher than for other models. KFC2b showed the best predictive accuracy for hot spot residues (True Positive Rate: TPR = 0.62) among all methods other than KFC2a, and the False Positive Rate (FPR = 0.15) was comparable with other highly predictive methods. PMID:21735484

Zhu, Xiaolei; Mitchell, Julie C

2011-07-06

132

LASER ABLATION-INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY STUDY AT THE 222-S LABORATORY USING HOT-CELL GLOVE BOX PROTOTYPE SYSTEM  

SciTech Connect

This report describes the installation, testing, and acceptance of the Waste Treatment and Immobilization Plant (WTP) procured laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES) system for remotely analyzing high-level waste (HLW) samples in a hot cell environment. The work was completed by the Analytical Process Development (APD) group in accordance with Task Order 2005-003; ATS MP 1027, Management Plan for Waste Treatment Plant Project Work Performed by Analytical Technical Services. The APD group at the 222-S Laboratory demonstrated acceptable turnaround time (TAT) and provide sufficient data to assess sensitivity, accuracy, and precision of the LA-ICP-AES method.

SEIDEL CM; JAIN J; OWENS JW

2009-02-23

133

LASER ABLATION-INDUCTIVELY COUPLED PLASMA-ATOMIC EMISSION SPECTROSCOPY STUDY AT THE 222-S LABORATORY USING HOT-CELL GLOVE BOX PROTOTYPE SYSTEM  

SciTech Connect

This report describes the installation, testing and acceptance of the Waste Treatment and Immobilization Plant procured laser ablation-inductively coupled plasma-atomic emission spectroscopy (LA-ICP-AES) system for remotely analyzing high-level waste samples in a hot cell environment. The 2005-003; ATS MP 1027, Management Plan for Waste Treatment Plant Project Work Performed by Analytical Technical Services. The APD group at the 222-S laboratory demonstrated acceptable turnaround time (TAT) and provide sufficient data to assess sensitivity, accuracy, and precision of the LA-ICP-AES method.

LOCKREM LL; OWENS JW; SEIDEL CM

2009-03-26

134

Laboratory studies of stratospheric bromine chemistry: Kinetics of the reactions of bromine monoxide with nitrogen dioxide and atomic oxygen  

SciTech Connect

A laser flash photolysis - long path absorption - technique has been employed to study the kinetics of the reaction BrO+NO2+M(k[sub 16]) yields products as a function of temperature (248-346 K), pressure (16-800 Torr), and buffer gas identity (N2, CF4). 351 nm photolysis of NO2/Br2/N2 mixtures generated BrO. The BrO decay in the presence of excess NO2 was followed by UV absorption at 338.3 nm. The reaction is in the falloff regime between third and second order over the entire range of conditions investigated. This is the first study where temperature dependent measurements of k[sub 16](P,T) have been reported at pressures greater than 12 Torr; hence, these results help constrain choices of k[sub 16](P,T) for use in modeling stratospheric BrO(x) chemistry. The kinetics of the important stratospheric reaction BrO+O(P-3)(k[sub 14]) yields Br+O2 in N2 buffer gas have been studied as a function of temperature (233-328 K) and pressure (25-150 Torr) using a novel dual laser flash photolysis/long path absorption/resonance fluorescence technique. 248 nm pulsed laser photolysis of Br2/O3/N2 mixtures produces O atoms in excess over Br2. After a delay sufficient for BrO to be generated, a 532 nm laser pulse photolysis a small fraction of the O3 to generate O(P-3). The decay of O(P-3) in the presence of an excess, known concentration of BrO, as determined by UV absorption at 338.3 nm and by numerical simulation, is then followed by time-resoved atomic resonance fluorescence spectroscopy. The experimental results have shown the reaction kinetics to be independent of pressure, to increase with decreasing temperature, and to be faster than suggested by the only previous (indirect) measurement. The resulting Anhenius expression for k[sub 14](T) is k[sub 14](T) = 1.64 x 10(exp -11) exp(263/T) cm(exp 3) molecule(exp-1)s(exp -1). The absolute accuracy of k[sub 14](T) at any temperature within the range studied is estimated to be +/- 25%.

Thorn, R.P.

1993-01-01

135

Sporadic metal atom and ion layers and their connection to chemistry and thermal structure in the mesopause region at Arecibo  

NASA Astrophysics Data System (ADS)

We present an analysis of two separate and distinct sporadic layer events in the mesosphere and lower thermosphere region above the Arecibo Observatory. These layers were observed in both neutral K and ionic Ca+ with lidars, and in electron density with incoherent scatter radar. Temperature profiles were determined from the K lidar. One sporadic event was a high altitude layer, in which both atomic and ion sporadic layers were positioned above 100 km altitude. This represents a relatively common sporadic layer visible in both ions and neutrals at Arecibo. The other observation was less typical, with a lower altitude and more diffuse sporadic E layer, extending from below 90 km to above 95 km, which dissipated coincident with growth of a sporadic neutral K layer. We analyze these separate events using a temperature-dependent chemical model, which employs commonly accepted chemical processes. We find that the model successfully reproduces the high altitude layer of June 12-13, 2002. The result shows a temperature dependence related to the chemical lifetimes of the metallic constituents, and that the neutral layer would not have formed had the temperature profile matched that of the MSIS-90 model. Second, the temperature dependent chemistry model also reproduced K+ in close agreement with electron densities on June 14-15, 2002. However, the modeled neutrals do not agree well with the observation above 90 km, and it likely requires inclusion of dynamical forcing and advection. We speculate that model and observational deficiencies, primarily exclusion of dynamics such as advection and wave interactions, are the likely shortcomings in the failure to reproduce the observations.

Delgado, Rubén; Friedman, Jonathan S.; Fentzke, Jonathan T.; Raizada, Shikha; Tepley, Craig A.; Zhou, Qihou

2012-01-01

136

Laser-fluorescent determination of traces of cobalt in dry residues of solutions with atomization in a hot hollow cathode  

Microsoft Academic Search

A discharge with a hollow cathode has been successfully applied to the solution of different problems in analysis of condensed media. In this case, depending on the problem solved, either a discharge with a hot [i, 2] or a cooled [3-5] hollow cathode is used in combination with recording of the emission [2-4] or absorption [5] signal of the determined

O. S. Lunev; D. E. Maksimov; S. V. Oshemkov; A. N. Rudnevskii

1990-01-01

137

Atoms Chemistry review  

NSDL National Science Digital Library

See the videos we watched in class (or review for your next exam) here To play the review game we will do in class, click below then click on Periodic Table Review Eureeka home To watch videos Sodium Video Element song Element song Alkali metal video Brainiac metalsSchool Island ...

Mckinnon

2009-06-11

138

Exchange and polarization effects in the elementary excitation spectrum of a hydrogen atom immersed in a hot plasma  

NASA Astrophysics Data System (ADS)

A computation of the one-particle hydrogenic Green's function for a partially ionized plasma of hydrogen atoms, electrons, and protons at high temperatures is presented. The method involves an evaluation of the mass operator in the Dyson equation to include proper self-energy parts to 'all orders' in the screened interaction; the operator characterizes the effective micropotential felt by the atom in the plasma and determines the particle properties associated with the atomic subsystem. The effects of center-of-mass motion on the level shifts and profiles and the onset of plasma instabilities are investigated.

Dharma-Wardana, M. W. C.; Grimaldi, F.; Lecourt, A.; Pellissier, J.-L.

1980-01-01

139

Confectionary Chemistry.  

ERIC Educational Resources Information Center

|Presents activities and demonstrations that enable teachers to use various types of confections as tactile experiences to spark chemistry students' interest and generate enthusiasm for learning. Presents uses of candy in teaching about atomic structure, spontaneous nuclear decay, chemical formulas, fractoluminescence, the effect of a molecular…

Levine, Elise Hilf

1996-01-01

140

Chemistry Activities  

NSDL National Science Digital Library

This collection of resource features demonstrations, laboratory investigations, teaching tips, worksheets and other chemistry-related activities. Materials include investigations of mols, nuclear energy, the periodic table, weight and mass, elements, calculations, equations, pH, atomic weight, half-lives, and reactions.

141

Chemistry on Stamps.  

ERIC Educational Resources Information Center

|Suggests how postage stamps can be incorporated into chemistry teaching. Categories considered include emergence of chemistry as a science, metric system, atoms (and molecules and ions), stoichiometry, energy relationships in chemical systems, chemical bonding, nuclear chemistry, biochemistry, geochemistry, matter (gases, liquids, and solids),…

Schreck, James O.

1986-01-01

142

Hot Sauce Hot Spots  

NSDL National Science Digital Library

In this activity, learners model hot spot island formation, orientation and progression with condiments. Learners squirt a thick condiment sauce on a coarsely woven fabric to model how volcanic island hot spots form.

Muller, Eric

2007-01-01

143

Merit of ground-state electronegativities; a reply to ''Comments on 'Introduction to the chemistry of fractionally charged atoms: Electronegativity' ''  

SciTech Connect

The arguments presented in the Comment by Liebman and Huheey are shown to be incorrect. The operational equivalence of Mulliken ground-state electronegativities and Pauling electronegativities is demonstrated for neutral atoms. It is shown that ground-state electronegativities and valence-state electronegativities for both neutral atoms and ions are also operationally equivalent. A single electronegativity scale based on Mulliken ground-state electronegativities may therefore be used for neutral atoms, ions, and fractionally charged atoms, as originally implied in the paper by Lackner and Zweig.

Lackner, K.S.; Zweig, G.

1987-09-01

144

Direct electrothermal atomic absorption spectrometry determination of nickel in sea water using multiple hot injection and Zeeman correction  

Microsoft Academic Search

Methods for the direct determination of Ni in sea water samples by ETAAS were developed using Zeeman effect background correction system (ZEBC) and a multi-injection technique. A mass of palladium nitrate of 2.5 ?g (for an injection volume of 100 ?l) was used as chemical modifier. The optimum pyrolysis and atomization temperatures were 1700 and 2100°C, respectively. The characteristic mass

Pilar Bermejo-Barrera; Jorge Moreda-Piñeiro; Antonio Moreda-Piñeiro; Adela Bermejo-Barrera

1998-01-01

145

The Development of Dalton's Atomic Theory as a Case Study in the History of Science: Reflections for Educators in Chemistry  

ERIC Educational Resources Information Center

|The inclusion of the history of science in science curricula--and specially, in the curricula of science teachers--is a trend that has been followed in several countries. The reasons advanced for the study of the history of science are manifold. This paper presents a case study in the history of chemistry, on the early developments of John…

Viana, Helio Elael Bonini; Porto, Paulo Alves

2010-01-01

146

Exoplanet Equilibrium Chemistry Calculations  

NASA Astrophysics Data System (ADS)

Recently, Agundez et al. (2012, A&A 548, A73) used a chemical kinetics code to study a model HD 209458b (equilibrium temperature of 1450 K, assuming full redistribution and 0 albedo). They found that thermochemistry dominates most of the dayside, but that significant compositional gradients may exist across the dayside. We calculate equilibrium-chemistry molecular abundances for several model exoplanets, using NASA's open-source Chemical Equilibrium Abundances code (McBride and Gordon 1996). We vary the degree of radiation redistribution to the dark side, ranging from total redistribution to instantaneous reradiation. Atomically, both the solar abundance multiple and the carbon fraction vary. Planet substellar temperatures range from just above 1200 K, where photochemistry should no longer be important, to those of hot planets (3000 K). We present synthetic abundance images for the key spectroscopic molecules CO, CH4, and H2O for several hot-Jupiter model planets. This work was supported by the NASA Planetary Atmospheres grant NNX12AI69G.

Blumenthal, Sarah; Harrington, J.; Bowman, M.; Blecic, J.

2013-10-01

147

Determination of the branching ratios for the reaction of hot H atoms with BrCN and CICN.  

SciTech Connect

The relative rates for the reaction of translationally energetic H atoms with XCN to yield HNC + X, HCN + X, and HX + CN, where X is Br or Cl, have been determined using time- and frequency-resolved absorption spectroscopy. The H atoms were created with an average translational energy of 92 kJ mol{sup -1} by the laser photolysis of CH{sub 3}SH at a wavelength of 248 nm. The measurements were carried out at a total pressure of several torr. The dominant channel for each reaction system was the production of hydrogen isocyanide, HNC. The relative branching ratios for H + BrCN and H + ClCN were determined to be 0.85/0.13/0.017 and 0.74/0.25/0.01 for the HNC/HCN/HX + CN channels, respectively. The ratio of the total reaction cross sections, {sigma}{sub XCN}, was found to be {sigma}{sub BrCN}/{sigma}{sub ClCN} = 0.84.

Decker, B. K.; He, G.; Tokue, I.; Macdonald, R. G.; Chemistry

2001-01-01

148

Merit of ground-state electronegativities; a reply to ``Comments on `Introduction to the chemistry of fractionally charged atoms: Electronegativity' ''  

Microsoft Academic Search

The arguments presented in the Comment by Liebman and Huheey are shown to be incorrect. The operational equivalence of Mulliken ground-state electronegativities and Pauling electronegativities is demonstrated for neutral atoms. It is shown that ground-state electronegativities and valence-state electronegativities for both neutral atoms and ions are also operationally equivalent. A single electronegativity scale based on Mulliken ground-state electronegativities may therefore

Klaus S. Lackner; George Zweig

1987-01-01

149

CHEMISTRY IN EVAPORATING ICES-UNEXPLORED TERRITORY  

SciTech Connect

We suggest that three-body chemistry may occur in warm high-density gas evaporating in transient co-desorption events on interstellar ices. Using a highly idealized computational model we explore the chemical conversion from simple species of the ice to more complex species containing several heavy atoms, as a function of density and of adopted three-body rate coefficients. We predict that there is a wide range of densities and rate coefficients in which a significant chemical conversion may occur. We discuss the implications of this idea for the astrochemistry of hot cores.

Cecchi-Pestellini, Cesare [INAF-Osservatorio Astronomico di Cagliari, Strada n.54, Loc. Poggio dei Pini, 09012 Capoterra (Italy); Rawlings, Jonathan M. C.; Viti, Serena; Williams, David A., E-mail: ccp@ca.astro.i, E-mail: jcr@star.ucl.ac.u, E-mail: sv@star.ucl.ac.u, E-mail: daw@star.ucl.ac.u [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2010-12-20

150

Pressure and electrical resistivity measurements on hot expanded nickel: Comparisons with quantum molecular dynamics simulations and average atom approaches  

SciTech Connect

We present experimental results on pressure and resistivity on expanded nickel at a density of 0.1 g/cm{sup 3} and temperature of a few eV. These data, corresponding to the warm dense matter regime, are used to benchmark different theoretical approaches. A comparison is presented between fully three-dimensional quantum molecular dynamics (QMD) methods, based on density functional theory, with average atom methods, that are essentially one dimensional. In this regime the evaluation of the thermodynamic properties as well as electrical properties is difficult due to the concurrence of density and thermal effects which directly drive the metal-nonmetal transition. Experimental pressures and resistivities are given in a tabular form with temperatures deduced from QMD simulations.

Clerouin, Jean; Starrett, Charles; Faussurier, Gerald; Blancard, Christophe; Noiret, Pierre; Renaudin, Patrick [CEA-DAM-DIF, Bruyeres Le Chatel, 91297 Arpajon Cedex (France)

2010-10-15

151

The Relationship Between Atomic and Oxide Ion Formation From Sputtered Particles During SIMS and The Chemistry of The Substrate Material. (Invited)  

NASA Astrophysics Data System (ADS)

It is well known that the chemical composition of a substance can influence the instrumental mass bias in secondary ion mass spectrometry (SIMS) [1][2] and the matrix chemistry influences relative sensitivity factors for many compounds [3][4]. When samples are smaller than the primary beam size, the chemistry of the substrate, and the matrix of the sample, influence the secondary ion yields. There are numerous applications where this can occur. Even the relative production of simple molecular species can be influenced by the substrate chemistry by preferential binding to the atoms from the region above the sample making the desired simple molecular ion less likely to occur. We have performed a study of the influence of substrate material on sensitivity factors. Substrates of C, Si, and Au, were used for measurements of Th, and U ions and their oxide and dioxide ions. Oxygen backfilling was also used for some measurements (see Figure 1). Correlations exist, in the case where oxygen backfilling was not used, with the dissociation energies of the substrate element oxides and the element oxide ions from the particles. This correlation can be observed in Figure 2. A complete set of data thus far collected will be presented. References [1] EH Hauri,, AM Shaw, JH Wang, JE Dixon, PL King, C Mandeville, “Chem. Geo.”, 235, (2006) pp. 352-365 [2] IC Lyon, JM Saxton, G Turner, R Hinton, “Rapid Comm. in Mass Spec.”, 8 (10), (1994), pp. 837-843 [3] RG Wilson, FA Stevie, and CW Magee Secondary-ion mass spec. Wiley-interscience, New York (1989). ISBN No.: 0 471 51945 6 [4] AJ Fahey, “Mass Spec. and Ion Proc.”, 176, (1998), pp. 63-76 Figure 1: Oxide signals with O-flooding on 3 different substrates. Figure 2: Oxide signals without O-flooding on 3 different substrates.

Fahey, A. J.; Zeissler, C.; Newbury, D.; Davis, J.; Lindstrom, R.

2010-12-01

152

How Many Atomic Layers of Zinc Are in a Galvanized Iron Coating? An Experiment for General Chemistry Laboratory  

ERIC Educational Resources Information Center

|This article describes an experiment using a novel gasometric assembly to determine the thickness and number of atomic layers of zinc coating on galvanized iron substrates. Students solved this problem through three stages. In the first stage, students were encouraged to find a suitable acidic concentration through the guided-inquiry approach. In…

Yang, Shui-Ping

2007-01-01

153

Zen Hot Dog Molecules  

ERIC Educational Resources Information Center

|Substituted cycloalkanes with one branch illustrating each topic in an instructional unit can serve as summaries or reviews in courses of organic chemistry. The hungry Zen master told the hot dog vendor to make him one with everything. You can do the same for your students.|

Ryan, Dennis

2009-01-01

154

The Role of Size Exclusion Chromatography-Flame Atomic Absorption Spectrometry in the Treatment Chemistry of Potable Water  

Microsoft Academic Search

The percentage composition of Al13, [AlO4Al12(OH)24(H2O)12]7+, in water treatment coagulants is an important criterion in the development and use of polymeric coagulants. Polymeric coagulants are generally used in cold climates or with highly turbid waters. Size exclusion chromatography–flame atomic absorption spectrometry (SEC-FAAS) can separate Al13 and monomeric Al within 6 min. The percentage composition of Al13 and monomeric Al is

Marina C. Koether

2002-01-01

155

Hot Science: Hot rocks  

NSDL National Science Digital Library

This site explores two kinds of igneous rock, pumice and granite. Pumice is an example of extrusive igneous rock, while granite is an example of intrusive igneous rock. Intrusive indicates that the magma was forced close to the surface, but then cooled more slowly underneath the surface. The question, "How hot is Lava?" is linked to an explanation of the heat of lava, why it must be sampled when it is very hot, and how the samples are taken.

156

Atmospheric chemistry of t-CF3CH=CHCl: products and mechanisms of the gas-phase reactions with chlorine atoms and hydroxyl radicals.  

PubMed

FTIR-smog chamber techniques were used to study the products and mechanisms of the Cl atom and OH radical initiated oxidation of trans-3,3,3-trifluoro-1-chloro-propene, t-CF(3)CH=CHCl, in 700 Torr of air or N(2)/O(2) diluent at 296 ± 2 K. The reactions of Cl atoms and OH radicals with t-CF(3)CH=CHCl occur via addition to the >C=C< double bond; chlorine atoms add 15 ± 5% at the terminal carbon and 85 ± 5% at the central carbon, OH radicals add approximately 40% at the terminal carbon and 60% at the central carbon. The major products in the Cl atom initiated oxidation of t-CF(3)CH=CHCl were CF(3)CHClCHO and CF(3)C(O)CHCl(2), minor products were CF(3)CHO, HCOCl and CF(3)COCl. The yields of CF(3)C(O)CHCl(2), CF(3)CHClCOCl and CF(3)COCl increased at the expense of CF(3)CHO, HCOCl and CF(3)CHClCHO as the O(2) partial pressure was increased over the range 10-700 Torr. Chemical activation plays a significant role in the fate of CF(3)CH(O)CHCl(2) and CF(3)CClHCHClO radicals. In addition to reaction with O(2) to yield CF(3)COCl and HO(2) the major competing fate of CF(3)CHClO is Cl elimination to give CF(3)CHO (not C-C bond scission as previously thought). As part of this study k(Cl + CF(3)C(O)CHCl(2)) = (2.3 ± 0.3) × 10(-14) and k(Cl + CF(3)CHClCHO) = (7.5 ± 2.0) × 10(-12) cm(3) molecule(-1) s(-1) were determined using relative rate techniques. Reaction with OH radicals is the major atmospheric sink for t-CF(3)CH=CHCl. Chlorine atom elimination giving the enol CF(3)CH=CHOH appears to be the sole atmospheric fate of the CF(3)CHCHClOH radicals. The yield of CF(3)COOH in the atmospheric oxidation of t-CF(3)CH=CHCl will be negligible (<2%). The results are discussed with respect to the atmospheric chemistry and environmental impact of t-CF(3)CH=CHCl. PMID:22187719

Andersen, M P Sulbaek; Nielsen, O J; Hurley, M D; Wallington, T J

2011-12-20

157

Multiply-charged ions and interstellar chemistry.  

PubMed

Gaseous molecules and ions, and even dust grains, can accumulate charge in the interstellar medium (ISM) by harvesting the energy of UV photons, cosmic rays, helium ions and metastable atoms. This Perspective views the various modes of gas-phase formation of multiply-charged cations and the possible impact of their reactions on the chemical and ionization structure of the ISM, in the light of what is still very limited knowledge. Emphasis is given to gas-phase reactions of multiply-charged cations with atoms, molecules and electrons that lead to charge reduction, charge separation and chemical bond formation and these are examined for multiply-charged atoms, small molecules, hydrocarbons, polycyclic aromatic hydrocarbons and fullerenes, primarily as dications but also as a function of charge state. The increased electrostatic interaction due to multiple charge is seen to promote bonding to individual charge sites on large molecules (e.g. fullerenes) and allow ensuing "surface" chemistry under the influence of Coulomb repulsion. The unique ability of multiply charged cations to undergo charge separation reactions, either unimolecular or bimolecular, can feature in the production in the ISM of internally cold, but translationally hot, cations of lower charge state or hot atoms that may provide the driving force for subsequent chemical reactions in what is otherwise an ultracold environment. Available chemical kinetic models that account for the role of multiply-charged ions in the ISM are few and of limited scope and the observation of these ions in the ISM has remained elusive. PMID:21869973

Böhme, Diethard Kurt

2011-08-25

158

Chemistry at corners and edges: Generation and adsorption of H atoms on the surface of MgO nanocubes  

SciTech Connect

We used UV light to generate site-selective O{sup -} hole centers at three-coordinated corner oxygen sites on MgO nanocubes. These highly reactive O{sup -} radicals split H{sub 2} homolytically and, in the course of this reaction, become hydroxylated and produce hydrogen atoms. The hydrogen atoms adsorb predominantly at cube edges and dissociate into surface-trapped electrons and protons. We propose that the experimentally observed (H{sup +})(e{sup -}) centers are formed adjacent to the hydroxyl groups generated in the homolytic splitting process and can be defined as (H{sup +}){sub 3C}{center_dot}{center_dot}{center_dot}(e{sup -})(H{sup +}){sub NC} centers where 3C and NC refer to the coordination numbers of the corresponding hydroxylated oxygen sites. Our ab initio embedded cluster calculations reveal that the electronic properties of (H{sup +}){sub 3C}{center_dot}{center_dot}{center_dot}(e{sup -})(H{sup +}){sub 4C} centers situated along MgO nanocube edges are consistent with both the electron-paramagnetic-resonance signal parameters and the reported optical-absorption properties. The transformation of corner O{sup -} centers into the (H{sup +}){sub 3C}{center_dot}{center_dot}{center_dot}(e{sup -})(H{sup +}){sub NC}-type centers prevents their recombination with electronic surface centers and, hence, significantly alters the electronic structure of MgO nanocubes by introducing shallow electron traps.

Sterrer, Martin; Berger, Thomas; Diwald, Oliver; Knoezinger, Erich; Sushko, Peter V.; Shluger, Alexander L. [Department of Chemical Physics, Fritz-Haber-Institute of the Max-Planck-Society, Faradayweg 4-6, D-14195 Berlin (Germany); Institute of Materials Chemistry, Vienna University of Technology, Veterinaerplatz 1/GA, A-1210 Vienna (Austria); Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

2005-08-08

159

Atomic scale studies of the chemistry of the Cu/MgO l brace 111 r brace heterophase interface  

SciTech Connect

The Cu/MgO (111) heterophase interface is studied using a combination of transmission electron microscopy, high resolution electron microscopy and atom-probe field-ion microscopy techniques. Wire and foil specimens of a Cu-2.8 at.% Mg alloy were internally oxidized to produce MgO precipitates at a number density of 5{center dot}10{sup 15}Cm{sup {minus}3} with a mean diameter of {approx}200 {Angstrom}. The MgO precipitates have a semicoherent interface with the Cu matrix and they exhibit a cube-on-cube orientation relationship. The octahedral-shaped MgO precipitates were analyzed using APFIM by dissecting along a <111> direction on an atomic scale. In this manner an MgO precipitate, with a (111) plane perpendicular to the axis of the APFIM, is uncovered after the Cu matrix has been mass analyzed. It was found that the terminating (222) plane of an MgO precipitate is pure oxygen, and the second (222) plane is pure Mg.

Jang, H.; Seidman, D.N. (Northwestern Univ., Evanston, IL (United States)); Merkle, K.L. (Argonne National Lab., IL (United States))

1992-01-01

160

Surface chemistry, structure, and electronic properties from microns to the atomic scale of axially doped semiconductor nanowires.  

PubMed

Using both synchrotron-based photoemission electron microscopy/spectroscopy and scanning tunneling microscopy/spectroscopy, we obtain a complete picture of the surface composition, morphology, and electronic structure of InP nanowires. Characterization is done at all relevant length scales from micrometer to nanometer. We investigate nanowire surfaces with native oxide and molecular adsorbates resulting from exposure to ambient air. Atomic hydrogen exposure at elevated temperatures which leads to the removal of surface oxides while leaving the crystalline part of the wire intact was also studied. We show how surface chemical composition will seriously influence nanowire electronic properties. However, opposite to, for example, Ge nanowires, water or sulfur molecules adsorbed on the exterior oxidized surfaces are of less relevance. Instead, it is the final few atomic layers of the oxide which plays the most significant role by strongly negatively doping the surface. The InP nanowires in air are rather insensitive to their chemical surroundings in contrast to what is often assumed for nanowires. Our measurements allow us to draw a complete energy diagram depicting both band gap and differences in electron affinity across an axial nanowire p-n junction. Our findings thus give a robust set of quantitative values relating surface chemical composition to specific electronic properties highly relevant for simulating the performance of nanoscale devices. PMID:23062066

Hjort, Martin; Wallentin, Jesper; Timm, Rainer; Zakharov, Alexei A; Håkanson, Ulf; Andersen, Jesper N; Lundgren, Edvin; Samuelson, Lars; Borgström, Magnus T; Mikkelsen, Anders

2012-10-24

161

Analogies in chemistry textbooks  

Microsoft Academic Search

This study combines a critical analysis of analogies found in eight chemistry textbooks used by Australian senior high school students with the views of the textbook authors about analogies in chemistry textbooks and teaching. Sixty?two analogies were identified which described abstract chemical concepts such as atomic structure and collision theory. A range of styles, including pictorial analogies, were identified and

Rodney B. Thiele; David F. Treagust

1995-01-01

162

Chemistry of americium  

Microsoft Academic Search

Essential features of the descriptive chemistry of americium are reviewed. Chapter titles are: discovery, atomic and nuclear properties, collateral reading, production and uses, chemistry in aqueous solution, metal, alloys, and compounds, and, recovery, separation, purification. Author and subject indexes are included. (JCB)

Schulz

1976-01-01

163

Chemistry: Experiments, Demonstrations and Other Activities Suggested for Chemistry.  

ERIC Educational Resources Information Center

This publication is a handbook used in conjunction with the course of study in chemistry developed through the New York State Education Department and The University of the State of New York. It contains experiments, demonstrations, and other activities for a chemistry course. Areas covered include the science of chemistry, the atomic structure of…

New York State Education Dept., Albany. Bureau of Secondary Curriculum Development.

164

XPS study of the surface chemistry of conventional hot-dip galvanised pure Zn, galvanneal and Zn–Al alloy coatings on steel  

Microsoft Academic Search

This study uses X-ray photoelectron spectroscopy (XPS) to analyse the outer surfaces of galvanised, galfan and galvanneal metallic coatings obtained by hot dipping. Considerable aluminium segregation towards the surface, principally as Al2O3, has been seen in all the studied coatings. The aluminium content on the surface was surprisingly similar to or even greater than the zinc content, which is the

S Feliu; V Barranco

2003-01-01

165

Numerical Simulation of Delft-Jet-in-Hot-Coflow (DJHC) Flames Using the Eddy Dissipation Concept Model for Turbulence–Chemistry Interaction  

Microsoft Academic Search

In this paper, we report results of a numerical investigation of turbulent natural gas combustion for a jet in a coflow of\\u000a lean combustion products in the Delft-Jet-in-Hot-Coflow (DJHC) burner which emulates MILD (Moderate and Intense Low Oxygen\\u000a Dilution) combustion behavior. The focus is on assessing the performance of the Eddy Dissipation Concept (EDC) model in combination\\u000a with two-equation turbulence

Ashoke De; Ernst Oldenhof; Pratap Sathiah; Dirk Roekaerts

2011-01-01

166

Metabolic conditions of lactating Friesian cows during the hot season in the Po valley. 2. Blood minerals and acid-base chemistry  

Microsoft Academic Search

In two consecutive summers, 21 and 18 cows respectively were monitored for acid-base chemistry and some blood minerals, to\\u000a assess their variation according to the level of heat stress at different stages of lactation. During both years, the cows\\u000a were monitored according to their lactation phase (early, mid-, and late) at the beginning of the summer. Climatic conditions\\u000a were described

Luigi Calamari; Fabio Abeni; Ferdinando Calegari; Luigi Stefanini

2007-01-01

167

Exotic Atoms and Muonium  

NASA Astrophysics Data System (ADS)

In exotic atoms, one of the atomic electrons is replaced by a negatively charged particle, whereas muonium consists of a positive muon and an electron. After a general review of the theoretical and experimental aspects, the present knowledge of this field is summarized. These include muonium and the application of the muon spin resonance method in solid-state physics and chemistry, muonic hydrogen atoms, muonic molecules and muon-catalyzed fusion, pionic hydrogen atoms and their use in chemistry, testing quantum electrodynamics on heavy muonic atoms, measuring particle and nuclear properties using hadronic atoms, and testing basic symmetry principles with antiprotonic helium atoms and antihydrogen.

Horváth, D.

168

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals Web site "was established as part of an (ongoing) project at Purdue University to develop 'visualization modules' for general chemistry students." Using the Chime plug-in, which allows unique and stunning visualizations, visitors can learn what an atomic orbital is; what the 1s, 2s, 3s, 2p, 3p, and 3d orbitals are; what hybrid orbitals are; and more. The combination of easy-to-read descriptions and educational graphics make the site a great learning resource for high school and even college level chemistry students.

2007-06-05

169

Manipulation of gold colloidal nanoparticles with atomic force microscopy in dynamic mode: influence of particle-substrate chemistry and morphology, and of operating conditions.  

PubMed

One key component in the assembly of nanoparticles is their precise positioning to enable the creation of new complex nano-objects. Controlling the nanoscale interactions is crucial for the prediction and understanding of the behaviour of nanoparticles (NPs) during their assembly. In the present work, we have manipulated bare and functionalized gold nanoparticles on flat and patterned silicon and silicon coated substrates with dynamic atomic force microscopy (AFM). Under ambient conditions, the particles adhere to silicon until a critical drive amplitude is reached by oscillations of the probing tip. Beyond that threshold, the particles start to follow different directions, depending on their geometry, size and adhesion to the substrate. Higher and respectively, lower mobility was observed when the gold particles were coated with methyl (-CH(3)) and hydroxyl (-OH) terminated thiol groups. This major result suggests that the adhesion of the particles to the substrate is strongly reduced by the presence of hydrophobic interfaces. The influence of critical parameters on the manipulation was investigated and discussed viz. the shape, size and grafting of the NPs, as well as the surface chemistry and the patterning of the substrate, and finally the operating conditions (temperature, humidity and scan velocity). Whereas the operating conditions and substrate structure are shown to have a strong effect on the mobility of the particles, we did not find any differences when manipulating ordered vs random distributed particles. PMID:21977418

Darwich, Samer; Mougin, Karine; Rao, Akshata; Gnecco, Enrico; Jayaraman, Shrisudersan; Haidara, Hamidou

2011-02-04

170

Atmospheric chemistry of CF3CH2OCH3: Reaction with chlorine atoms and OH radicals, kinetics, degradation mechanism and global warming potential  

NASA Astrophysics Data System (ADS)

FTIR smog chamber techniques were used to measure k(Cl + CF3CH2OCH3) = (2.28 ± 0.44) × 10-11 and k(OH + CF3CH2OCH3) = (4.9 ± 1.3) × 10-13 cm3 molecule-1 s-1 in 700 Torr total pressure of air at 296 ± 2 K. The atmospheric lifetime of CF3CH2OCH3 is estimated at 25 days. Reaction of Cl atoms with CF3CH2OCH3 proceeds 79 ± 4% at the CH3 group and 22 ± 2% at the CH2 group. Reaction with OH radicals proceeds 55 ± 5% at the CH3 group yielding CF3CH2OCHO and 45 ± 5% at the CH2 group yielding COF2 and CH3OCHO as primary oxidation products. The infrared spectrum of CF3CH(O)OCH3 was measured and a global warming potential GWP100 = 8 was estimated. The atmospheric chemistry and environmental impact of CF3CH2OCH3 is discussed in context of the use of hydrofluoroethers as CFC substitutes.

Østerstrøm, Freja From; Nielsen, Ole John; Sulbaek Andersen, Mads P.; Wallington, Timothy J.

2012-02-01

171

Manipulation of gold colloidal nanoparticles with atomic force microscopy in dynamic mode: influence of particle-substrate chemistry and morphology, and of operating conditions  

PubMed Central

Summary One key component in the assembly of nanoparticles is their precise positioning to enable the creation of new complex nano-objects. Controlling the nanoscale interactions is crucial for the prediction and understanding of the behaviour of nanoparticles (NPs) during their assembly. In the present work, we have manipulated bare and functionalized gold nanoparticles on flat and patterned silicon and silicon coated substrates with dynamic atomic force microscopy (AFM). Under ambient conditions, the particles adhere to silicon until a critical drive amplitude is reached by oscillations of the probing tip. Beyond that threshold, the particles start to follow different directions, depending on their geometry, size and adhesion to the substrate. Higher and respectively, lower mobility was observed when the gold particles were coated with methyl (–CH3) and hydroxyl (–OH) terminated thiol groups. This major result suggests that the adhesion of the particles to the substrate is strongly reduced by the presence of hydrophobic interfaces. The influence of critical parameters on the manipulation was investigated and discussed viz. the shape, size and grafting of the NPs, as well as the surface chemistry and the patterning of the substrate, and finally the operating conditions (temperature, humidity and scan velocity). Whereas the operating conditions and substrate structure are shown to have a strong effect on the mobility of the particles, we did not find any differences when manipulating ordered vs random distributed particles.

Darwich, Samer; Rao, Akshata; Gnecco, Enrico; Jayaraman, Shrisudersan; Haidara, Hamidou

2011-01-01

172

Atomic-Scale Design of Iron Fischer-Tropsch Catalysts: A Combined Computational Chemistry, Experimental, and Microkinetic Modeling Approach  

SciTech Connect

Efforts during this second year focused on four areas: (1) continued searching and summarizing of published Fischer-Tropsch synthesis (FTS) mechanistic and kinetic studies of FTS reactions on iron catalysts; (2) investigation of CO adsorption/desorption and temperature programmed hydrogenation (TPH) of carbonaceous species after FTS on unsupported iron and alumina-supported iron catalysts; (3) activity tests of alumina-supported iron catalysts in a fixed bed reactor; (4) sequential design of experiments, for the collection of rate data in a Berty CSTR reactor, and nonlinear-regression analysis to obtain kinetic parameters. Literature sources describing mechanistic and kinetic studies of Fischer-Tropsch synthesis on iron catalysts were compiled in a review. Temperature-programmed desorption/reaction methods (the latter using mass-spectrometry detection and also thermogravimetric analyzer (TGA)) were utilized to study CO adsorption/-desorption on supported and unsupported iron catalysts. Molecular and dissociative adsorptions of CO occur on iron catalysts at 25-150 C. The amounts adsorbed and bond strengths of adsorption are influenced by supports and promoters. That CO adsorbs dissociatively on polycrystalline Fe at temperatures well below those of FT reaction indicates that CO dissociation is facile and unlikely to be the rate-limiting step during FTS. Carbonaceous species formed after FT reaction for only 5 minutes at 200 C were initially hydrogenated under mild, isothermal condition (200 C and 1 atm), followed by TPH to 800 C. During the mild, isothermal hydrogenation, only about 0.1-0.2 mL of atomic carbon is apparently removed, while during TPH to 800 C multilayer equivalents of atomic, polymeric, carbidic, and graphitic carbons are removed. Rates of CO conversion on alumina-supported iron catalysts at 220-260 C and 20 atm are correlated well by a Langmuir-Hinshelwood expression, derived assuming carbon hydrogenation to CH and OH recombination to water to be rate-determining steps. In the coming year, studies will focus on quantitative determination of the rates of kinetically-relevant elementary steps on Fe catalysts with/without K and Pt promoters and at various levels of Al{sub 2}O{sub 3} support, providing a database for understanding (1) effects of promoter and support on elementary kinetic parameters and (2) for validation of computational models that incorporate effects of surface structure and promoters. Kinetic parameters will be incorporated into a microkinetics model, enabling prediction of rate without invoking assumptions, e.g. of a rate-determining step or a most-abundant surface intermediate. Calculations using periodic, self-consistent Density Functional Theory (DFT) methods were performed on two model surfaces: (1) Fe(110) with 1/4 ML subsurface carbon, and (2) Fe(110) with 1/4 ML Pt adatoms. Reaction networks for FTS on these systems were characterized in full detail by evaluating the thermodynamics and kinetics of each elementary step. We discovered that subsurface C stabilizes all the reactive intermediates, in contrast to Pt, which destabilizes most of them. A comparative study of the reactivities of the modified-Fe surfaces against pure Fe is expected to yield a more comprehensive understanding of promotion mechanisms for FTS on Fe.

Manos Mavrikakis; James A. Dumesic; Amit A. Gokhale; Rahul P. Nabar; Calvin H. Bartholomew; Hu Zou; Brian Critchfield

2006-03-03

173

NUCLEAR CHEMISTRY ANNUAL REPORT 1970  

SciTech Connect

Papers are presented for the following topics: (1) Nuclear Structure and Nuclear Properties - (a) Nuclear Spectroscopy and Radioactivity; (b) Nuclear Reactions and Scattering; (c) Nuclear Theory; and (d) Fission. (2) Chemical and Atomic Physics - (a) Atomic and Molecular Spectroscopy; and (b) Hyperfine Interactions. (3) Physical, Inorganic, and Analytical Chemistry - (a) X-Ray Crystallography; (b) Physical and Inorganic Chemistry; (c) Radiation Chemistry; and (d) Chemical Engineering. (4) Instrumentation and Systems Development.

Authors, Various

1971-05-01

174

Astronomical chemistry.  

PubMed

The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic. PMID:21128763

Klemperer, William

2011-01-01

175

Astronomical Chemistry  

NASA Astrophysics Data System (ADS)

The discovery of polar polyatomic molecules in higher-density regions of the interstellar medium by means of their rotational emission detected by radioastronomy has changed our conception of the universe from essentially atomic to highly molecular. We discuss models for molecule formation, emphasizing the general lack of thermodynamic equilibrium. Detailed chemical kinetics is needed to understand molecule formation as well as destruction. Ion molecule reactions appear to be an important class for the generally low temperatures of the interstellar medium. The need for the intrinsically high-quality factor of rotational transitions to definitively pin down molecular emitters has been well established by radioastronomy. The observation of abundant molecular ions both positive and, as recently observed, negative provides benchmarks for chemical kinetic schemes. Of considerable importance in guiding our understanding of astronomical chemistry is the fact that the larger molecules (with more than five atoms) are all organic.

Klemperer, William

2011-05-01

176

Method of producing excited states of atomic nuclei. [by bombarding material with x rays or electrons generated by an x-ray tube or electron gun and chemical separation by hot atoms  

Microsoft Academic Search

A method is claimed of producing excited states of atomic nuclei which comprises bombarding atoms with x rays or electrons, characterized in that (1) in the atoms selected to be produced in the excited state of their nuclei, (a) the difference between the nuclear excitation energy and the difference between the binding energies of adequately selected two electron orbits is

M. Morita; R. Morita

1976-01-01

177

Hot Flashes  

MedlinePLUS

Hot flashes Basics In-Depth Multimedia Expert Answers Resources Reprints A single copy of this article may be reprinted for personal, noncommercial use only. Hot flashes By Mayo Clinic staff Original Article: http:// ...

178

Partial Characterization of a Novel Amphibian Hemoglobin as a Model for Graduate Student Investigation on Peptide Chemistry, Mass Spectrometry, and Atomic Force Microscopy  

ERIC Educational Resources Information Center

|Graduate students in chemistry, and in biological and biomedical fields must learn the fundamentals and practices of peptide and protein chemistry as early as possible. A project-oriented approach was conducted by first-year M.Sc and Ph.D students in biological sciences. A blind glass slide containing a cellular smear and an aqueous cellular…

Bemquerer, Marcelo P.; Macedo, Jessica K. A.; Ribeiro, Ana Carolina J.; Carvalho, Andrea C.; Silva, Debora O. C.; Braz, Juliana M.; Medeiros, Kelliane A.; Sallet, Lunalva A. P.; Campos, Pollyanna F.; Prates, Maura V.; Silva, Luciano P.

2012-01-01

179

Partial Characterization of a Novel Amphibian Hemoglobin as a Model for Graduate Student Investigation on Peptide Chemistry, Mass Spectrometry, and Atomic Force Microscopy  

ERIC Educational Resources Information Center

Graduate students in chemistry, and in biological and biomedical fields must learn the fundamentals and practices of peptide and protein chemistry as early as possible. A project-oriented approach was conducted by first-year M.Sc and Ph.D students in biological sciences. A blind glass slide containing a cellular smear and an aqueous cellular…

Bemquerer, Marcelo P.; Macedo, Jessica K. A.; Ribeiro, Ana Carolina J.; Carvalho, Andrea C.; Silva, Debora O. C.; Braz, Juliana M.; Medeiros, Kelliane A.; Sallet, Lunalva A. P.; Campos, Pollyanna F.; Prates, Maura V.; Silva, Luciano P.

2012-01-01

180

Nuclear chemistry. Annual report, 1974  

SciTech Connect

The 1974 Nuclear Chemistry Annual Report contains information on research in the following areas: nuclear science (nuclear spectroscopy and radioactivity, nuclear reactions and scattering, nuclear theory); chemical and atomic physics (heavy ion-induced atomic reactions, atomic and molecular spectroscopy, photoelectron spectroscopy and hyperfine interactions); physical, inorganic, and analytical chemistry (x-ray crystallography, physical and inorganic chemistry, geochemistry); and instrumentation. Thesis abstracts, 1974 publication titles, and an author index are also included. Papers having a significant amount of information are listed separately by title. (RWR)

Conzett, H.E.; Edelstein, N.M.; Tsang, C.F. (eds.)

1975-07-01

181

Green Chemistry Teaching Resources  

NSDL National Science Digital Library

The American Chemical Society (ACS) has created these excellent resources via the Green Chemistry Institute and the ACS Education Division. The goal of these materials is "to increase awareness and understanding of Green Chemistry principles, alternatives, practices, and benefits within traditional educational institutions and among practicing scientists." In the Online Resources section, visitors will find downloadable pocket guides to basic green chemistry principles, "Greener Education Materials for Chemists" from the University of Oregon, and more. Perhaps the best section of the site is Activities and Experiments, where visitors can look over activities like "Gassing Up Without Air Pollution" and "Cleaning Up With Atom Economy."

2012-10-26

182

Green Chemistry Teaching Resources  

NSDL National Science Digital Library

The American Chemical Society (ACS) has created these excellent resources via the Green Chemistry Institute and the ACS Education Division. The goal of these materials is "to increase awareness and understanding of Green Chemistry principles, alternatives, practices, and benefits within traditional educational institutions and among practicing scientists." In the Online Resources section, visitors will find downloadable pocket guides to basic green chemistry principles, "Greener Education Materials for Chemists" from the University of Oregon, and more. Perhaps the best section of the site is Activities and Experiments, where visitors can look over activities like "Gassing Up Without Air Pollution" and "Cleaning Up With Atom Economy."

183

Shape-selective catalysts for Fischer-Tropsch chemistry : atomic layer deposition of active catalytic metals. Activity report : January 1, 2005 - September 30, 2005.  

SciTech Connect

Argonne National Laboratory is carrying out a research program to create, prepare, and evaluate catalysts to promote Fischer-Tropsch (FT) chemistry - specifically, the reaction of hydrogen with carbon monoxide to form long-chain hydrocarbons. In addition to needing high activity, it is desirable that the catalysts have high selectivity and stability with respect to both mechanical strength and aging properties. The broad goal is to produce diesel fraction components and avoiding excess yields of both light hydrocarbons and heavy waxes. Originally the goal was to prepare shape-selective catalysts that would limit the formation of long-chain products and yet retain the active metal sites in a protected 'cage.' Such catalysts were prepared with silica-containing fractal cages. The activity was essentially the same as that of catalysts without the cages. We are currently awaiting follow-up experiments to determine the attrition strength of these catalysts. A second experimental stage was undertaken to prepare and evaluate active FT catalysts formed by atomic-layer deposition [ALD] of active components on supported membranes and particulate supports. The concept was that of depositing active metals (i.e. ruthenium, iron or cobalt) upon membranes with well defined flow channels of small diameter and length such that the catalytic activity and product molecular weight distribution could be controlled. In order to rapidly evaluate the catalytic membranes, the ALD coating processes were performed in an 'exploratory mode' in which ALD procedures from the literature appropriate for coating flat surfaces were applied to the high surface area membranes. Consequently, the Fe and Ru loadings in the membranes were likely to be smaller than those expected for complete monolayer coverage. In addition, there was likely to be significant variation in the Fe and Ru loading among the membranes due to difficulties in nucleating these materials on the aluminum oxide surfaces. The first series of experiments using coated membranes demonstrated that the technology needed further improvement. Specifically, observed catalytic FT activity was low. This low activity appeared to be due to: (1) low available surface area, (2) atomic deposition techniques that needed improvements, and (3) insufficient preconditioning of the catalyst surface prior to FT testing. Therefore, experimentation was expanded to the use of particulate silica supports having defined channels and reasonably high surface area. This later experimentation will be discussed in the next progress report. Subsequently, we plan to evaluate membranes after the ALD techniques are improved with a careful study to control and quantify the Fe and Ru loadings. The preconditioning of these surfaces will also be further developed. (A number of improvements have been made with particulate supports; they will be discussed in the subsequent report.) In support of the above, there was an opportunity to undertake a short study of cobalt/promoter/support interaction using the Advanced Photon Source (APS) of Argonne. Five catalysts and a reference cobalt oxide were characterized during a temperature programmed EXAFS/XANES experimental study with the combined effort of Argonne and the Center for Applied Energy Research (CAER) of the University of Kentucky. This project was completed, and it resulted in an extensive understanding of the preconditioning step of reducing Co-containing FT catalysts. A copy of the resulting manuscript has been submitted and accepted for publication. A similar project was undertaken with iron-containing FT catalysts; the data is currently being studied.

Cronauer, D. C. (Chemical Sciences and Engineering Division)

2011-04-15

184

Art in Chemistry: Chemistry in Art. Second Edition  

ERIC Educational Resources Information Center

This textbook integrates chemistry and art with hands-on activities and fascinating demonstrations that enable students to see and understand how the science of chemistry is involved in the creation of art. It investigates such topics as color integrated with electromagnetic radiation, atoms, and ions; paints integrated with classes of matter,…

Greenberg, Barbara R.; Patterson, Dianne

2008-01-01

185

Art in Chemistry: Chemistry in Art. Second Edition  

ERIC Educational Resources Information Center

|This textbook integrates chemistry and art with hands-on activities and fascinating demonstrations that enable students to see and understand how the science of chemistry is involved in the creation of art. It investigates such topics as color integrated with electromagnetic radiation, atoms, and ions; paints integrated with classes of matter,…

Greenberg, Barbara R.; Patterson, Dianne

2008-01-01

186

Application of laser induced electron impact ionization to the deposition chemistry in the hot-wire chemical vapor deposition process with SiH4-NH3 gas mixtures.  

PubMed

The application of a laser-induced electron impact (LIEI) ionization source in studying the gas-phase chemistry of the SiH(4)/NH(3) hot-wire chemical vapor deposition (HWCVD) system has been investigated. The LIEI source is achieved by directing an unfocused laser beam containing both 118 nm (10.5 eV) vacuum ultraviolet (VUV) and 355 nm UV radiations to the repeller plate in a time-of-flight mass spectrometer. Comparison of the LIEI source with the conventional 118 nm VUV single-photon ionization (SPI) method has demonstrated that the intensities of the chemical species with ionization potentials (IP) above 10.5 eV, e.g., H(2), N(2) and He, have been significantly enhanced with the incorporation of the LIEI source. It is found that the SPI source due to the 118 nm VUV light coexists in the LIEI source. This allows simultaneous observations of parent ions with enhanced intensity from VUV SPI and their "fingerprint" fragmentation ions from LIEI. It is, therefore, an effective tool to diagnose the gas-phase chemical species involved with both NH(3) and SiH(4) in the HWCVD reactor. In using the LIEI source to SiH(4), NH(3) and their mixtures, it has been shown that the NH(3) decomposition is suppressed with the addition of SiH(4) molecules. Examination of the NH(3) decomposition percentage and the time to reach the N(2) and H(2) steady-state intensities for various NH(3)/SiH(4) mixtures suggests that the extent of the suppression is enhanced with more SiH(4) content in the mixture. With increasing filament temperatures, the negative effect of SiH(4) becomes less important. PMID:17869128

Eustergerling, Brett; Hèden, Martin; Shi, Yujun

2007-08-24

187

Hot Groups.  

ERIC Educational Resources Information Center

|Collaborators sparked by creative ideas and obsessed by a common task may not realize they're part of a "hot group"--a term coined by business professors Harold J. Leavitt and Jean Lipman-Blumen. Spawned by group decision making and employee empowerment, hot groups can flourish in education settings. They're typically small, short lived, and goal…

Vail, Kathleen

1996-01-01

188

Hot and Cold  

NSDL National Science Digital Library

In this activity, learners explore temperature changes from chemical reactions by mixing urea with water in one flask and mixing calcium chloride with water in another flask. They observe that the urea flask gets cold and the calcium chloride flask gets hot. The main idea is that some chemical processes release heat energy and are exothermic, while some chemical processes absorb heat energy and are endothermic. This activity is currently used in the Nature of Matter Unit in OMSI's Chemistry Lab. Cost estimates are per 100 learners.

Industry, Oregon M.

1997-01-01

189

From Chemistry To Culture  

Microsoft Academic Search

Chemistry deals with atoms and molecules, and anybody who views interactions of matter on that level and who successfully resolves problems on that level is a chemist. Many environmental problems can be solved by chemists working, technically speaking, at the molecular level. But when the solution is presented to the public at the socio-economic level or in socio-economic terms, the

W. A. Bridgeo; H. J. Labelle

1991-01-01

190

Heat treatment and properties of high-speed steel 10R6M5MP produced by atomization and hot extrusion  

Microsoft Academic Search

With heat treatment to a given hardness, high-speed steels manufactured by atomization have higher mechanical properties than standard steel of similar composition due to the homogeneous fine-grained structure and even distribution of finely dispersed carbide phase. These steels should be quenched from temperatures 20–30° lower than for standard steels.

M. N. Goryushina; N. N. Gavrikov; I. B. Bolonkina; G. E. Titenskaya

1980-01-01

191

Green Chemistry  

NSDL National Science Digital Library

This special feature page from the American Chemical Society (ACS) showcases the up-and-coming field of "green chemistry," that is, the development of chemical products and processes that eliminate or reduce the use and generation of hazardous substances. A list of principles behind green chemistry, a searchable bibliography of green chemistry references, green chemistry links (including conferences), and an online preview of the ACS-published book Real-World Cases in Green Chemistry are all found at the site. Five video clips on green chemistry from the standpoint of academia, industry, and small business are also featured (Windows Media Player). This page comes from ACS's Green Chemistry Project, a three-year educational project to develop and disseminate green chemistry educational materials for graduate and undergraduate chemistry students. Check back often for updates.

2002-01-01

192

Hot water, hot rocks, hot science  

Microsoft Academic Search

Of the numerous energy sources, several important ones come from deep inside the earth. Coal, oil, and natural gas have formed over time through the interaction of enormous pressures and temperatures on organic material. Geothermal energy - steam and hot water - is also a product of these subsurface forces. Even the raw material for nuclear energy, uranium, comes from

Wesolowski

1995-01-01

193

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents background information, laboratory procedures, classroom materials/activities, and chemistry experiments. Topics include sublimation, electronegativity, electrolysis, experimental aspects of strontianite, halide test, evaluation of present and future computer programs in chemistry, formula building, care of glass/saturated calomel…

School Science Review, 1983

1983-01-01

194

Chemistry Notes.  

ERIC Educational Resources Information Center

|Presents background information, laboratory procedures, classroom materials/activities, and chemistry experiments. Topics include sublimation, electronegativity, electrolysis, experimental aspects of strontianite, halide test, evaluation of present and future computer programs in chemistry, formula building, care of glass/saturated calomel…

School Science Review, 1983

1983-01-01

195

Organic Chemistry  

NSDL National Science Digital Library

R. H. Logan, an chemistry instructor at North Lake College, created this introduction to organic chemistry. The introduction covers a eight types of organic compounds, including Alkanes, Alkyl Halides, and Acyl Compounds (forthcoming); Conformational Analysis and Stereoisomerism; and Instrumental Analysis of Organic Compounds, as well an extensive lesson in general chemistry.

196

Forensic Chemistry  

Microsoft Academic Search

“Forensic chemistry” is a broad term that, if taken literally, would encompass most of the functions within a crime laboratory.\\u000a Techniques used in forensic chemistry are also used by the toxicology and trace analysis sections. However, forensic chemistry\\u000a generally refers to controlled substance or drug analysis.

Donnell Christian

197

Forensic Chemistry  

Microsoft Academic Search

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is

Suzanne Bell

2009-01-01

198

Chemistry Notes.  

ERIC Educational Resources Information Center

|Presents background information, laboratory procedures, classroom materials/activities, and experiments for chemistry. Topics include superheavy elements, polarizing power and chemistry of alkali metals, particulate carbon from combustion, tips for the chemistry laboratory, interesting/colorful experiments, behavior of bismuth (III) iodine, and…

School Science Review, 1982

1982-01-01

199

EUV and x-ray instrumentation for spectrometry, polarimetry, and imaging in hot plasma diagnostics, atomic physics, and x-ray microscopy: a status report  

NASA Astrophysics Data System (ADS)

The Instrumentation Program at Physics Department of the University of Nevada, Reno, USA is based on results of the development and study of one of first glass capillary optics devices in period from 1974 to earlier 90s in USSR/Russia (by V. Kantsyrev, O. Ananyin, Yu. Bykovsky and collaborators). The main direction of our program is the development of several techniques for extreme ultraviolet, soft x-ray and x-ray optical instrumentation, for spectroscopic diagnostics of hot plasmas, spectroscopic studies of interaction of multicharged ion beams with matter, biomedical x-ray microscopy. Our currently-developed instruments include: EUV polarimeter/spectrometer with GCC polarizing and focusing elements; a high resolution, a high-sensitivity EUV and x-ray spectrometer with focusing GCC, that also serves as a high- transmission window for differential vacuum pumping; a prototype of new multiband, two dimensional EUV and x-ray imaging spectrometer for plasma diagnostics; a pinhole camera with GCC using as a hard x-ray filter; a soft x-ray spectrograph with MLM for plasma diagnostics.

Kantsyrev, Victor L.; Bauer, Bruno S.; Phaneuf, Ronald A.

1998-12-01

200

Characterization of diamond films deposited by hot-filament CVD using CF4 as doping gas by Raman spectroscopy, FTIR spectroscopy, and atomic force microscopy  

NASA Astrophysics Data System (ADS)

Diamond films have been deposited by hot-filament CVD on silicon using either a gas mixture of pure methane-hydrogen or a mixture of methane-hydrogen and carbon-tetrafluoride, for the study of the influence of the fluorine radicals in the growth process. Raman spectra shows that the fluorine is effective in the etching of non-diamond bonds since the corresponding Raman shift at 1550 cm-1 due to sp2 was not observed in the films deposited with the CF4/CH4 gas mixture. Also the FTIR spectra of these films show a better transmittance in the range from 500 cm-1 to 4000 cm-1, and an apparent increase of the SiC layer thickness. Using the same thermodynamical conditions, with the CF4/CH4 gas mixture diamond films of high quality are deposited at a higher growth rate. AFM measurements of the surface morphology indicates apparently the same vertical roughness in both kinds of films but large lateral coalescence in the films produced with CF4-content.

Trava-Airoldi, Vladimir J.; Rodrigues, C. R.; Fukui, Masahiko; Baranauskas, Vitor

1992-11-01

201

Chemistry of Transactinides  

NASA Astrophysics Data System (ADS)

In this chapter, the chemical properties of the man-made transactinide elements rutherfordium, Rf (element 104), dubnium, Db (element 105), seaborgium, Sg (element 106), bohrium, Bh (element 107), hassium, Hs (element 108), and copernicium, Cn (element 112) are reviewed, and prospects for chemical characterizations of even heavier elements are discussed. The experimental methods to perform rapid chemical separations on the time scale of seconds are presented and comments are given on the special situation with the transactinides where chemistry has to be studied with single atoms. It follows a description of theoretical predictions and selected experimental results on the chemistry of elements 104 through 108, and element 112.

Kratz, J. V.

202

CLUSTER CHEMISTRY  

SciTech Connect

Metal cluster chemistry is one of the most rapidly developing areas of inorganic and organometallic chemistry. Prior to 1960 only a few metal clusters were well characterized. However, shortly after the early development of boron cluster chemistry, the field of metal cluster chemistry began to grow at a very rapid rate and a structural and a qualitative theoretical understanding of clusters came quickly. Analyzed here is the chemistry and the general significance of clusters with particular emphasis on the cluster research within my group. The importance of coordinately unsaturated, very reactive metal clusters is the major subject of discussion.

Muetterties, Earl L.

1980-05-01

203

Forensic Chemistry  

NASA Astrophysics Data System (ADS)

Forensic chemistry is unique among chemical sciences in that its research, practice, and presentation must meet the needs of both the scientific and the legal communities. As such, forensic chemistry research is applied and derivative by nature and design, and it emphasizes metrology (the science of measurement) and validation. Forensic chemistry has moved away from its analytical roots and is incorporating a broader spectrum of chemical sciences. Existing forensic practices are being revisited as the purview of forensic chemistry extends outward from drug analysis and toxicology into such diverse areas as combustion chemistry, materials science, and pattern evidence.

Bell, Suzanne

2009-07-01

204

Synthesis and self-assembly of thermoresponsive PEG-b-PNIPAM-b-PCL ABC triblock copolymer through the combination of atom transfer radical polymerization, ring-opening polymerization, and click chemistry.  

PubMed

A well-defined thermoresponsive poly(ethylene glycol)-block-poly(N-isopropylacrylamide)-block-poly(?-caprolactone) (PEG(43)-b-PNIPAM(82)-b-PCL(87)) triblock copolymer was synthesized by combination of atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP), and click chemistry. The synthesis included the four steps, and all the structures of the polymers were determined. The thermoresponsive triblock copolymer can disperse in water at room temperature to form core-shell-corona micelles with the hydrophobic PCL block as core, the thermoresponsive PNIPAM block as shell, and the hydrophilic PEG block as corona. At temperatures above the lower critical solution temperature (LCST) of the PNIPAM block, the PNIPAM chains gradually collapse on the PCL core to shrink the size and change the structure of the resultant core-shell-corona micelles with temperature increasing. PMID:22082119

Chen, Jiucun; Liu, Mingzhu; Gong, Honghong; Huang, Yinjuan; Chen, Chen

2011-11-28

205

Source of Atomic Hydrogen in the Atmosphere of HD 209458b  

NASA Astrophysics Data System (ADS)

Atomic hydrogen loss at the top of HD 209458b's atmosphere has been recently suggested (Vidal-Madjar et al.). We have developed a one-dimensional model to study the chemistry in the upper atmosphere of this extrasolar ``hot Jupiter.'' The three most abundant elements (other than He) as well as four parent molecules are included in this model, viz., H, C, O, H2, CO, H2O, and CH4. The higher temperatures (~1000 K) and higher stellar irradiance (~6×105 W m-2) strongly enhance and modify the chemical reaction rates in this atmosphere. The main result is that the production of atomic hydrogen in the atmosphere is mainly driven by H2O photolysis, and the reaction of OH with H2, and is insensitive to the exact abundances of CO, H2O, and CH4. For comparison, the bulk H concentration for ``hot Jupiters'' is 3 orders of magnitude higher than that of Jupiter.

Liang, Mao-Chang; Parkinson, Christopher D.; Lee, Anthony Y.-T.; Yung, Yuk L.; Seager, Sara

2003-10-01

206

Hot Tickets  

ERIC Educational Resources Information Center

|This article describes the highlights of this year's BookExpo America (BEA) held at the Los Angeles Convention Center. The attendees at BEA had not minded that the air was recycled, the lighting was fluorescent, and the food was bad. The first hot book sighting came courtesy of Anne Rice. Michelle Moran, author of newly published novel, "The…

Fox, Bette-Lee; Hoffert, Barbara; Kuzyk, Raya; McCormack, Heather; Williams, Wilda

2008-01-01

207

HOT AIR  

NSDL National Science Digital Library

HOT AIR -- The graphical home page of THE ANNALS OF IMPROBABLE RESEARCH FROM MIT provides a different look at scientific research. Check out a schedule of AIR events, an art gallery, and SharewAIR--an interactive and up-to-the-minute moderated forum.

208

Molecular-beam study of gas-surface chemistry in the ion-assisted etching of silicon with atomic and molecular hydrogen and chlorine  

Microsoft Academic Search

Modulated molecular-beam mass spectrometry and quartz crystal microbalance techniques were used to study the etching of Si by the combinations of H\\/Hâ, Cl\\/Clâ, HCl, and Ar{sup +} ion bombardment at room temperature. Without ion bombardment, only H atoms etch Si spontaneously. While the addition of Cl or Clâ stopped H etching instantaneously, the addition of HCl had no effect. With

Mei-Chen Chuang; J. W. Coburn

1990-01-01

209

Martian corona: Nonthermal sources of hot heavy species  

Microsoft Academic Search

We have studied the production of hot O and C atoms, and hot CO2 and CO molecules in the Martian upper atmosphere and exosphere by dissociative recombination (DR) of O2+ and CO+ ions, and sputtering of the atmosphere by incident O+ pick-up ions. Production and collisional thermalization of the hot particles in the upper atmosphere are described by using a

F. Cipriani; F. Leblanc; J. J. Berthelier

2007-01-01

210

Reactions of Iron Atoms with Unsaturated Hydrocarbons.  

National Technical Information Service (NTIS)

Reactions of iron atoms with unsaturated hydrocarbons are described to further illustrate the chemistry of metal atoms, and the synthesis of several novel organometallic compounds by the codeposition techniques are reported. (Author)

D. L. Williams-Smith I. R. Wolf P. S. Skell

1972-01-01

211

Chemistry Notes.  

ERIC Educational Resources Information Center

|Outlines laboratory procedures, demonstrations, teaching suggestions, and content information related to chemistry. Topics include polarizing power; calorimetry and momentum; microcomputers in school chemistry; a constant-volume dispenser for liquids, floating magnets, and crystal lattices; preparation of chromium; and solvent polarity and…

School Science Review, 1981

1981-01-01

212

Atmospheric chemistry of sulfuryl fluoride: reaction with OH radicals, Cl atoms and O3, atmospheric lifetime, IR spectrum, and global warming potential.  

PubMed

Sulfuryl fluoride (SO2F2) is a radiatively active industrial chemical released into the atmosphere in significant (ktonne/ year) quantities. The potential for SO2F2 to contribute to radiative forcing of climate change needs to be assessed. Long path length FTIR/smog chamber techniques were used to investigate the kinetics of the gas-phase reactions of Cl atoms, OH radicals, and O3 with SO2F2, in 700 Torr total pressure of air or N2 at 296 +/- 1 K. Upper limits of k(Cl + SO2F2) < 9 x 10(-19), k(OH + SO2F2) < 1.7 x 10(-14) and k(O3 + SO2F2) < 5.5 x 10(-24) cm3 molecule(-1) s(-1) were determined. Reaction with Cl atoms, OH radicals, or O3 does not provide an efficient removal mechanism for SO2F2. The infrared spectrum of SO2F2 is reported and a radiative efficiency of 0.196 W m(-2) ppbv(-1) was calculated. Historic production data estimates are presented which provide an upper limit for expected atmospheric concentrations. The radiative forcing of climate change associated with emissions of SO2F2 depends critically on the atmospheric lifetime of SO2F2. Further research is urgently needed to define the magnitude of potential nonatmospheric sinks. PMID:19320159

Andersen, M P Sulbaek; Blake, D R; Rowland, F S; Hurley, M D; Wallington, T J

2009-02-15

213

Atomic scale studies of the chemistry of the Cu/MgO {l_brace}111{r_brace} heterophase interface  

SciTech Connect

The Cu/MgO [111] heterophase interface is studied using a combination of transmission electron microscopy, high resolution electron microscopy and atom-probe field-ion microscopy techniques. Wire and foil specimens of a Cu-2.8 at.% Mg alloy were internally oxidized to produce MgO precipitates at a number density of 5{center_dot}10{sup 15}Cm{sup {minus}3} with a mean diameter of {approx}200 {Angstrom}. The MgO precipitates have a semicoherent interface with the Cu matrix and they exhibit a cube-on-cube orientation relationship. The octahedral-shaped MgO precipitates were analyzed using APFIM by dissecting along a <111> direction on an atomic scale. In this manner an MgO precipitate, with a [111] plane perpendicular to the axis of the APFIM, is uncovered after the Cu matrix has been mass analyzed. It was found that the terminating [222] plane of an MgO precipitate is pure oxygen, and the second [222] plane is pure Mg.

Jang, H.; Seidman, D.N. [Northwestern Univ., Evanston, IL (United States); Merkle, K.L. [Argonne National Lab., IL (United States)

1992-08-01

214

Atmospheric chemistry of trans-CF 3CH CHCl: Kinetics of the gas-phase reactions with Cl atoms, OH radicals, and O 3  

Microsoft Academic Search

Long path length Fourier transform infrared (FTIR)–smog chamber techniques were used to study the kinetics of the gas-phase reactions of Cl atoms, OH radicals and O3 with trans-3,3,3-trifluoro-1-chloro-propene, t-CF3CHCHCl, in 700Torr total pressure at 295±2K. Values of k(Cl+t-CF3CHCHCl)=(5.22±0.72)×10?11cm3molecule?1s?1, k(OH+t-CF3CHCHCl)=(4.40±0.38)×10?13cm3molecule?1s?1 and k(O3+t-CF3CHCHCl)=(1.46±0.12)×10?21cm3molecule?1s?1, were established (quoted uncertainties are 2?; see Experimental section). The IR spectrum of t-CF3CHCHCl is reported. The atmospheric lifetime

M. P. Sulbaek Andersen; E. J. K. Nilsson; O. J. Nielsen; M. S. Johnson; M. D. Hurley; T. J. Wallington

2008-01-01

215

Atmospheric chemistry of CF 3CH 2CF 2CH 3 (HFC365mfc): Kinetics and mechanism of chlorine atom initiated oxidation, infrared spectrum, and global warming potential  

Microsoft Academic Search

Smog chamber\\/FTIR techniques were used to study the chlorine atom initiated oxidation of CF3CH2CF2CH3 in 700Torr of N2\\/O2 at 296K. Relative rate techniques were used to measure k(Cl+CF3CH2CF2CH3)=(1.02±0.14)×10?15cm3molecule?1s?1. The reaction proceeds via attack on the –CH3 group leading to formation of CF3CH2CF2CHO which in turn is oxidized to CF3CHO and COF2. The integrated IR band strength of CF3CH2CF2CH3 over the

Y. Inoue; M. Kawasaki; T. J. Wallington; M. D. Hurley

2008-01-01

216

The free radical chemistry of tert-butyl formate: rate constants for hydroxyl radical, hydrated electron and hydrogen atom reaction in aqueous solution  

NASA Astrophysics Data System (ADS)

Transients generated in situ by advanced oxidation technologies (AOTs) to destroy organic contaminants in ground and drinking water often give large concentrations of chemical by-products. These by-products may have adverse health effects, and can also interfere with the desired chemical removal by competing for the generated transients, thus lowering the overall efficiency of the remediation process. To allow for a quantitative evaluation of the influence of tert-butyl formate (TBF), a major by-product formed in the AOT destruction of methyl tert-butyl ether, rate constants for TBF reaction with the hydroxyl radical, the hydrated electron and the hydrogen atom in aqueous solution were measured in this study. Absolute values of (5.23+/-0.07)×108, (5.48+/-0.09)×108 and (3.58+/-0.07)×106M-1s-1, were determined at 22°C, respectively.

Hardison, D. Ransom; Cooper, William J.; Mezyk, Stephen P.; Bartels, David M.

2002-11-01

217

The gas phase chemistry of the formic acid radical cation [HCOOH][radical sign]+. Mechanism for exchange of the hydrogen atoms: a quantum chemical investigation  

NASA Astrophysics Data System (ADS)

The CH2O2[radical sign]+ potential energy surface has been (re)explored by ab initio quantum chemical calculations executed at the SD-CI/6-31G**//UHF/4-31G level of theory. Earlier labelling experiments had indicated that prior to the loss of H[radical sign] the hydrogen atoms in ionized formic acid, HCOOH[radical sign]+, can become positionally equivalent via an unknown pathway. Using ab initio molecular orbital calculations we have located a minimum energy reaction pathway for hydrogen exchange reactions which takes place close to the dissociation level and proceeds via flexible ion/dipole complexes. Along this path three equilibrium structures of different atom connectivity are found: HCOOH[radical sign]+, 1, ionized formic acid; two forms of the surprisingly stable ion/dipole complex HO[radical sign]·HCO+, 2, 3; and the distonic ion H2O---CO[radical sign]+, 4. Ion 1 is separated from ion 2 by a barrier of 142 kJ mol-1 and this barrier corresponds to a 2A' --> 2A'' surface crossing. The barrier for the proton transfer 3 --> 4 is only 25 kJ mol-1 relative to 3; the transformation HCOOH[radical sign]+ --> H2O---CO[radical sign]+, formally a 1,2-hydrogen shift, takes place via the ion/dipole complex HO[radical sign]·HCO+, H2O---C[radical sign]+ is the reacting configuration for decarbonylation and this reaction is calculated to take place at the dissociation limit in full agreement with experiment.

Ruttink, Paul J. A.; Burgers, Peter C.

1992-02-01

218

Chemistry in 1876: The Way It Was  

ERIC Educational Resources Information Center

|Provides a brief history of chemistry up to the founding of the American Chemical Society in 1876. Includes developments in the understanding of matter, phlogiston theory, atomic theory, and chemical reactions. (MLH)|

Bernheim, Robert A.

1976-01-01

219

A Green Chemistry Approach to Ibuprofen Piconol  

Microsoft Academic Search

Ibuprofen piconol synthesis has been described. The use of solid catalyst has demonstrated green chemistry approach with promoted atom economy of 94% compared to the reported 68%. DRL Publication No: 430.

C. M. Haricharan Raju; P. Naga Lakshmi; Ch. Srinivas; G. Om. Reddy; Palle V. R. Acharyulu

2005-01-01

220

Silicones—Basic chemistry and selected applications  

Microsoft Academic Search

The objective of this review is to provide a working knowledge of the chemistry of silicone compounds to the practicing chemist.\\u000a Although silicone compounds have been known for over 50 yr, the chemistry of these materials remains elusive to the average\\u000a formulating chemist. This is indeed unfortunate, since the chemistry of the silicon atom and resulting silicone compounds\\u000a is every

Anthony J. O'Lenick

2000-01-01

221

Cooperative Research in C1 Chemistry  

Microsoft Academic Search

C1 chemistry refers to the conversion of simple carbon-containing materials that contain one carbon atom per molecule into valuable products. The feedstocks for C1 chemistry include natural gas, carbon dioxide, carbon monoxide, methanol and synthesis gas (a mixture of carbon monoxide and hydrogen). Synthesis gas, or syngas, is produced primarily by the reaction of natural gas, which is principally methane,

Gerald P. Huffman

2000-01-01

222

Nuclear Chemistry, Science (Experimental): 5316.62.  

ERIC Educational Resources Information Center

|This nuclear chemistry module includes topics on atomic structure, instability of the nucleus, detection strengths and the uses of radioactive particles. Laboratory work stresses proper use of equipment and safe handling of radioactive materials. Students with a strong mathematics background may consider this course as advanced work in chemistry.…

Williams, Russell R.

223

Mechanisms Influencing "Hot-Wire" Deposition of Hydrogenated Amorphous Silicon  

SciTech Connect

Intrinsic hydrogenated amorphous silicon (a-Si:H) has been deposited using a hot tungsten filament in pure silane to drive the deposition chemistry--the ''hot-wire'' deposition method. The electronic and infrared properties of the film have been measured as a function of deposition parameters, leading to three principal conclusions. First, to obtain a high quality material, the Si atoms evaporated from the filament (distance L from the substrate) must react with silane (density ns) before reaching the substrate; this requires nsL greater than a critical value. Second, radical-radical reactions cause deterioration of film properties at high values of G(nsL),3 where G is the film growth rate; this requires G(nsL)3 less than a critical value. Finally, the film quality is a function of G, and as G is increased the substrate temperature must be correspondingly increased to obtain high film quality. By optimizing these parameters, we have produced films with excellent electronic properties (e.g., ambipolar diffusion length >200 nm) at >5 nm/s deposition rate. Based on these insights, formulas are also given for optimizing film properties in multiple-filament geometries and in diluted silane.

Molenbroek, E. C.; Mahan, A. H.; Gallagher, A.

1997-08-15

224

Catalytic Chemistry.  

ERIC Educational Resources Information Center

Describes an approach for making chemistry relevant to everyday life. Involves the study of kinetics using the decomposition of hydrogen peroxide by vegetable juices. Allows students to design and carry out experiments and then draw conclusions from their results. (JRH)

Borer, Londa; And Others

1996-01-01

225

Chemistry Notes.  

ERIC Educational Resources Information Center

Describes equipment, activities, and experiments useful in chemistry instruction, including among others, a rapid method to determine available chlorine in bleach, simple flame testing apparatus, and a simple apparatus demonstrating the technique of flash photolysis. (SK)

School Science Review, 1980

1980-01-01

226

Catalytic Chemistry.  

ERIC Educational Resources Information Center

|Describes an approach for making chemistry relevant to everyday life. Involves the study of kinetics using the decomposition of hydrogen peroxide by vegetable juices. Allows students to design and carry out experiments and then draw conclusions from their results. (JRH)|

Borer, Londa; And Others

1996-01-01

227

Nuclear Chemistry.  

ERIC Educational Resources Information Center

Provides a brief review of the latest developments in nuclear chemistry. Nuclear research today is directed toward increased activity in radiopharmaceuticals and formation of new isotopes by high-energy, heavy-ion collisions. (Author/BB)

Chemical and Engineering News, 1979

1979-01-01

228

Green Chemistry  

NSDL National Science Digital Library

Learn about a study in which participants discovered contaminants in their homes, and how green chemistry may provide alternatives to such everyday toxins, in this video adapted from Contaminated Without Consent.

Foundation, Wgbh E.

2011-03-21

229

Chemistry Notes.  

ERIC Educational Resources Information Center

|Describes 13 activities, experiments and demonstrations, including the preparation of iron (III) chloride, simple alpha-helix model, investigating camping gas, redox reactions of some organic compounds, a liquid crystal thermometer, and the oxidation number concept in organic chemistry. (JN)|

School Science Review, 1981

1981-01-01

230

Nuclear Chemistry.  

ERIC Educational Resources Information Center

|Provides a brief review of the latest developments in nuclear chemistry. Nuclear research today is directed toward increased activity in radiopharmaceuticals and formation of new isotopes by high-energy, heavy-ion collisions. (Author/BB)|

Chemical and Engineering News, 1979

1979-01-01

231

Chemistry Notes  

ERIC Educational Resources Information Center

|Several ideas are proposed for chemistry teachers to try in their classrooms. Subjects included are polymerization of acrylate, polymerization of styrene, conductivity, pollution, preparation of chlorine, redox equations, chemiluminescence, and molecular sieves. (PS)|

School Science Review, 1973

1973-01-01

232

Chemistry Notes.  

ERIC Educational Resources Information Center

|Describes equipment, activities, and experiments useful in chemistry instruction, including among others, a rapid method to determine available chlorine in bleach, simple flame testing apparatus, and a simple apparatus demonstrating the technique of flash photolysis. (SK)|

School Science Review, 1980

1980-01-01

233

Organosilicon Chemistry.  

National Technical Information Service (NTIS)

Several new aspects of the chemistry of silylenes, divalent reactive silicon intermediates, have been explored. Insertion reactions of dimethylsilylene into O-H bonds of primary, secondary, and tertiary alcohols were studied. This provides an efficient ro...

W. P. Weber

1982-01-01

234

Atomic-scale measurement of structure and chemistry of a single-unit-cell layer of LaAlO3 embedded in SrTiO3.  

PubMed

A single layer of LaAlO3 with a nominal thickness of one unit cell, which is sandwiched between a SrTiO3 substrate and a SrTiO3 capping layer, is quantitatively investigated by high-resolution transmission electron microscopy. By the use of an aberration-corrected electron microscope and by employing sophisticated numerical image simulation procedures, significant progress is made in two aspects. First, the structural as well as the chemical features of the interface are determined simultaneously on an atomic scale from the same specimen area. Second, the evaluation of the structural and chemical data is carried out in a fully quantitative way on the basis of the absolute image contrast, which has not been achieved so far in materials science investigations using high-resolution electron microscopy. Considering the strong influence of even subtle structural details on the electronic properties of interfaces in oxide materials, a fully quantitative interface analysis, which makes positional data available with picometer precision together with the related chemical information, can contribute to a better understanding of the functionality of such interfaces. PMID:23452378

Jia, Chun-Lin; Barthel, Juri; Gunkel, Felix; Dittmann, Regina; Hoffmann-Eifert, Susanne; Houben, Lothar; Lentzen, Markus; Thust, Andreas

2013-03-04

235

Surface-Functionalized and Surface-Functionalizable Poly(vinylidene fluoride) Graft Copolymer Membranes via Click Chemistry and Atom Transfer Radical Polymerization.  

PubMed

Poly(vinylidene fluoride) (PVDF) with azide-functionalized poly(glycidyl methacrylate) (PGMA) side chains (PVDF-g-P[GMA-(N(3))(OH)]) were synthesized via free radical-initiated graft copolymerization of glycidyl methacrylate (GMA) from ozone-pretreated PVDF backbone (PVDF-g-PGMA), followed by reaction of the oxirane rings in the GMA side chains with sodium azide. Alkyne-functionalized poly(N-isopropylacrylamide) (alkynyl-PNIPAM), prepared a priori by atom transfer radical polymerization (ATRP), was used for the click reaction with the azido-containing PGMA side chains of the PVDF-g-P[GMA-(N(3))(OH)] copolymer to give rise to the thermoresponsive PVDF-g-P[GMA-click-PNIPAM] copolymer. Both the PVDF-g-P[GMA-(N(3))(OH)] and PVDF-g-P[GMA-click-PNIPAM] copolymers can be readily cast into microporous membranes by phase inversion in an aqueous medium. The PVDF-g-P[GMA-(N(3))(OH)] microporous membranes with azido-containing surfaces could be further functionalized via surface click reaction with alkyne-terminated PNIPAM of controlled chain lengths to obtain the PVDF-g-P[GMA-click-PNIPAM](surface) microporous membranes. The surface composition and morphology of the PVDF-g-P[GMA-click-PNIPAM] membranes can be adjusted by the temperature of casting medium, while the flux through both types of membranes exhibits thermoresponsive behavior. PMID:21341769

Cai, Tao; Neoh, K G; Kang, E T; Teo, S L M

2011-02-22

236

Stratospheric chemistry  

SciTech Connect

Advances in stratospheric chemistry made by investigators in the United States from 1987 to 1990 are reviewed. Subject areas under consideration include photochemistry of the polar stratosphere, photochemistry of the global stratosphere, and assessments of inadvertent modification of the stratosphere by anthropogenic activity. Particular attention is given to early observations and theories, gas phase chemistry, Antarctic observations, Arctic observations, odd-oxygen, odd-hydrogen, odd-nitrogen, halogens, aerosols, modeling of stratospheric ozone, and reactive nitrogen effects.

Brune, W.H. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

237

Chemistry Tutorials  

NSDL National Science Digital Library

The California State University Stanislaus developed these interactive chemistry Web tutorials to assist college students in mass spectrometry, proton NMR chemical shifts, and more. With the many animations and figures, visitors will find assistance with the subtraction and absorption of light and with infrared absorption frequencies for numerous compounds. The titration tutorials simulate laboratory experiments without the hazards of dealing with chemicals. Students will also find a very informative lesson describing how to use Excel to record and analyze their chemistry data.

238

Atmospheric Chemistry in Extrasolar Giant Planets or The Cosmic Shoreline  

NASA Astrophysics Data System (ADS)

Title: Atmospheric Chemistry in Extrasolar Giant Planets. Metallicity and C/O ratio are potential observables in spectra of EGPs. Both address the mode of planetary formation. Metallicity reveals itself best in molecules composed of more than one “metal” atom, such as CO2. C/O ratio is more complicated. There are parallels between the chemistry generated by 1994’s SL9 impacts on Jupiter and the chemistry of EGPs. In both, a hot gas quenches by cooling and rarefaction. In SL9, the impact-heated gas exploded, expanded, and cooled. In EGPs, quenching is a consequence of vertical mixing. Products of SL9 included S2, CS2, HCN, C2H4, CO, CO2, and carbonaceous hazes. All of these might be expected in EGPs. Close-in planets differ from SL9 in the photochemical consequences of stellar UV. Primary photolysis of H2S, NH3, and H2O creates free radicals that react with H2 to make atomic H. Abundant H attacks CH4 and promotes formation of C2H2 and HCN, which readily polymerize to make hazes. It is likely that such a haze is observed in HD 189733b. Title: Cosmic Shoreline. Volatile escape is the classic existential problem of planetary atmospheres. The problem has gained new currency now that we can begin to study escape, or the cumulative effects of escape, from extrasolar planets seen in transit. Already some intriguing patterns have emerged. In particular, transiting EGPs appear to fit a pattern seen in our own Solar System. The data show that atmospheres are found where escape velocity is high and (i) solar heating is low or (ii) impact velocities are low. In either case, the boundary between planets with and without atmospheres --- the cosmic shoreline, as it were --- is a simple power law that extends from Pluto to Jupiters and beyond.

Zahnle, Kevin

2011-09-01

239

Chemistry-Nuclear Chemistry Division. Progress report, October 1980-September 1981  

SciTech Connect

This report describes major progress in the research and development programs pursued by the Chemistry-Nuclear Chemistry Division of the Los Alamos National Laboratory during FY 1981. Topics covered include advanced analytical methods, atmospheric chemistry and transport, biochemistry, biomedical research, medical radioisotopes research, element migration and fixation, nuclear waste isolation research, inorganic and structural chemistry, isotope separation, analysis and applications, the newly established Nuclear Magnetic Resonance Center, atomic and molecular collisions, molecular spectroscopy, nuclear cosmochemistry, nuclear structure and reactions, pion charge exchange, radiochemical separations, theoretical chemistry, and unclassified weapons research.

Ryan, R.R. (comp.)

1982-05-01

240

Have a Chemistry Field Day in Your Area.  

ERIC Educational Resources Information Center

Describes a full day of chemistry fun and competition for high school chemistry students. Notes teams have five students from each high school. Lists five competitive events for each team: titration, qualitative analysis, balancing equations, general chemistry quiz, and quantitative analysis with atomic absorption spectroscopy. (MVL)

Mattson, Bruce M.; And Others

1989-01-01

241

The World of Chemistry  

NSDL National Science Digital Library

One doesn't have to be a Glenn Seaborg or a Lord Ernest Rutherford to learn about chemistry, though it probably couldn't help to have some of their curiosity about the world of chemistry. Young chemists and their teachers will definitely benefit from this nice resource offered by the Annenberg Media project. This original video series was produced by the University of Maryland and the Educational Film Center, and it consists of 26 half-hour programs. With industrial and research chemists demonstrating a number of high-intensity experiments and processes, the series is quite a find. The installments include such titles as "Modeling the Unseen", "The Atom", and "The Busy Electron".

1990-01-01

242

Atoms in Astronomy.  

ERIC Educational Resources Information Center

This booklet is part of an American Astronomical Society curriculum project designed to provide teaching materials to teachers of secondary school chemistry, physics, and earth science. A Basic Topics section discusses atomic structure, emphasizing states of matter at high temperature and spectroscopic analysis of light from the stars. A section…

Blanchard, Paul A.

243

Hot tub folliculitis  

MedlinePLUS

Hot tub folliculitis is an infection of the skin around the lower part of the hair shaft ( ... Hot tub folliculitis is caused by the bacteria Pseudomonas aeruginosa . This form of bacteria survives in hot ...

244

Atmospheric chemistry of isoflurane, desflurane, and sevoflurane: kinetics and mechanisms of reactions with chlorine atoms and OH radicals and global warming potentials.  

PubMed

The smog chamber/Fourier-transform infrared spectroscopy (FTIR) technique was used to measure the rate coefficients k(Cl + CF(3)CHClOCHF(2), isoflurane) = (4.5 ± 0.8) × 10(-15), k(Cl + CF(3)CHFOCHF(2), desflurane) = (1.0 ± 0.3) × 10(-15), k(Cl + (CF(3))(2)CHOCH(2)F, sevoflurane) = (1.1 ± 0.1) × 10(-13), and k(OH + (CF(3))(2)CHOCH(2)F) = (3.5 ± 0.7) × 10(-14) cm(3) molecule(-1) in 700 Torr of N(2)/air diluent at 295 ± 2 K. An upper limit of 6 × 10(-17) cm(3) molecule(-1) was established for k(Cl + (CF(3))(2)CHOC(O)F). The laser photolysis/laser-induced fluorescence (LP/LIF) technique was employed to determine hydroxyl radical rate coefficients as a function of temperature (241-298 K): k(OH + CF(3)CHFOCHF(2)) = (7.05 ± 1.80) × 10(-13) exp[-(1551 ± 72)/T] cm(3) molecule(-1); k(296 ± 1 K) = (3.73 ± 0.08) × 10(-15) cm(3) molecule(-1), and k(OH + (CF(3))(2)CHOCH(2)F) = (9.98 ± 3.24) × 10(-13) exp[-(969 ± 82)/T] cm(3) molecule(-1); k(298 ± 1 K) = (3.94 ± 0.30) × 10(-14) cm(3) molecule(-1). The rate coefficient of k(OH + CF(3)CHClOCHF(2), 296 ± 1 K) = (1.45 ± 0.16) × 10(-14) cm(3) molecule(-1) was also determined. Chlorine atoms react with CF(3)CHFOCHF(2) via H-abstraction to give CF(3)CFOCHF(2) and CF(3)CHFOCF(2) radicals in yields of approximately 83% and 17%. The major atmospheric fate of the CF(3)C(O)FOCHF(2) alkoxy radical is decomposition via elimination of CF(3) to give FC(O)OCHF(2) and is unaffected by the method used to generate the CF(3)C(O)FOCHF(2) radicals. CF(3)CHFOCF(2) radicals add O(2) and are converted by subsequent reactions into CF(3)CHFOCF(2)O alkoxy radicals, which decompose to give COF(2) and CF(3)CHFO radicals. In 700 Torr of air 82% of CF(3)CHFO radicals undergo C-C scission to yield HC(O)F and CF(3) radicals with the remaining 18% reacting with O(2) to give CF(3)C(O)F. Atmospheric oxidation of (CF(3))(2)CHOCH(2)F gives (CF(3))(2)CHOC(O)F in a molar yield of 93 ± 6% with CF(3)C(O)CF(3) and HCOF as minor products. The IR spectra of (CF(3))(2)CHOC(O)F and FC(O)OCHF(2) are reported for the first time. The atmospheric lifetimes of CF(3)CHClOCHF(2), CF(3)CHFOCHF(2), and (CF(3))(2)CHOCH(2)F (sevoflurane) are estimated at 3.2, 14, and 1.1 years, respectively. The 100 year time horizon global warming potentials of isoflurane, desflurane, and sevoflurane are 510, 2540, and 130, respectively. The atmospheric degradation products of these anesthetics are not of environmental concern. PMID:22146013

Sulbaek Andersen, Mads P; Nielsen, Ole J; Karpichev, Boris; Wallington, Timothy J; Sander, Stanley P

2011-12-06

245

Electron scattering in hot-dense plasmas  

NASA Astrophysics Data System (ADS)

Hot-dense plasmas have direct industrial applications in inertial confinement fusion. We have used the convergent close-coupling (CCC) method to investigate electron scattering off hydrogen and helium atoms in a hot-dense weakly coupled (Debye) plasma. The Yukawa-type Debye-Hückel potential has been used to describe the plasma screening effects. Integrated excitation, total ionization and total cross sections have been calculated over a broad range of energies and various Debye lengths, D.

Zammit, Mark C.; Fursa, Dmitry V.; Bray, Igor

2012-11-01

246

Atom Probe Field Ion Microscopy  

Microsoft Academic Search

This book is one of the series of `Monographs on the physics and chemistry of materials', published by the Clarendon Press. Its title is perhaps unduly restrictive inasmuch as the identification of single atoms in the field ion microscope (Atom probe FIM) is merely the end stage in a long chain of computer-assisted operations plus the equally important task of

T Mulvey

1997-01-01

247

Chemistry Now  

NSDL National Science Digital Library

The National Science Foundation (NSF) recently teamed up with NBC and the National Science Teachers Association to celebrate the International Year of Chemistry. Their big joint project was to create Chemistry Now, a weekly online video series that uncovers and explains the science of common, physical objects. There are over two dozen short films here that cover topics like the chemistry of salt, grapheme, safety glass, and the common cheeseburger. All of the videos are lively and interesting, and they can be used in a wide range of classroom settings to provide visual and audio reinforcement of topics that might be addressed in course lectures and other activities. The videos are completely free and the site includes links to other organizations that have created similar videos.

2012-08-17

248

Atomic and molecular supernovae  

SciTech Connect

Atomic and molecular physics of supernovae is discussed with an emphasis on the importance of detailed treatments of the critical atomic and molecular processes with the best available atomic and molecular data. The observations of molecules in SN 1987A are interpreted through a combination of spectral and chemical modelings, leading to strong constraints on the mixing and nucleosynthesis of the supernova. The non-equilibrium chemistry is used to argue that carbon dust can form in the oxygen-rich clumps where the efficient molecular cooling makes the nucleation of dust grains possible. For Type Ia supernovae, the analyses of their nebular spectra lead to strong constraints on the supernova explosion models.

Liu, W.

1997-12-01

249

Unlocking the Atom  

NSDL National Science Digital Library

In this project, high school chemistry students investigate atomic structure from a historical perspective. Assuming the personas of eight legendary scientists and their assistants, students stage a mock gathering to explore the evolution of the atomic model. This role-playing activity may also serve as a template for weaving the rich history of science into other subject areas. The project culminates in individually written news stories about the "meeting of the minds," an assignment that allows students to weave history, modern atomic theory, and their own twist on events that might transpire if deceased scientists could converse.

Miller, Jacqueline S.; Craft, Jennifer L.

2007-02-01

250

The Quantum Mechanical Basis of Conceptual Chemistry  

Microsoft Academic Search

Summary.  An experimentalist approaching theory for an understanding of conceptual chemistry that can be related to measurable properties, focuses on the electron density distribution. One finds in the topology of the electron density the definition of an atom, of the bonding between atoms, and of the boundary condition for the extension of quantum mechanics to an open system – to an

Richard F. W. Bader

2005-01-01

251

Ion chemistry in space.  

PubMed

We review the gas-phase chemistry in extraterrestrial space that is driven by reactions with atomic and molecular ions. Ions are ubiquitous in space and are potentially responsible for the formation of increasingly complex interstellar molecules. Until recently, positively charged atoms and molecules were the only ions known in space; however, this situation has changed with the discovery of various molecular anions. This review covers not only the observation, distribution and reactions of ions in space, but also laboratory-based experimental and theoretical methods for studying these ions. Recent results from space-based instruments, such as those on the Cassini-Huygens space mission and the Herschel Space Observatory, are highlighted. PMID:22790651

Larsson, M; Geppert, W D; Nyman, G

2012-05-23

252

Common Chemistry  

NSDL National Science Digital Library

A web resource that contains Chemical Abstracts Service (CAS) Registry Numbers for approximately 7,800 chemicals of widespread general public interest. Common Chemistry is helpful to non-chemists who know either a name or CAS Registry Number® of a common chemical and want to pair both pieces of information.

Chemical Abstracts Service (CAS)

253

Chemistry Notes  

ERIC Educational Resources Information Center

Short articles on the kinetics of the hydrogen peroxide-iodide ion reaction, simulation of fluidization catalysis, the use of Newman projection diagrams to represent steric relationships in organic chemistry, the use of synthetic substrates for proteolytic enzyme reactions, and two simple clock reactions"--hydrolysis of halogenoalkanes and…

School Science Review, 1972

1972-01-01

254

Chemistry Notes  

ERIC Educational Resources Information Center

|Short articles on the kinetics of the hydrogen peroxide-iodide ion reaction, simulation of fluidization catalysis, the use of Newman projection diagrams to represent steric relationships in organic chemistry, the use of synthetic substrates for proteolytic enzyme reactions, and two simple clock reactions"--hydrolysis of halogenoalkanes and…

School Science Review, 1972

1972-01-01

255

Chemistry Notes.  

ERIC Educational Resources Information Center

|Presents chemistry experiments, laboratory procedures, demonstrations, teaching suggestions, and classroom materials/activities. These include: game for teaching ionic formulas; method for balancing equations; description of useful redox series; computer programs (with listings) for water electrolysis simulation and for determining chemical…

School Science Review, 1983

1983-01-01

256

Chemistry Notes.  

ERIC Educational Resources Information Center

|Presents chemistry experiments, laboratory procedures, demonstrations, and classroom materials/activities. These include: experiments on colloids, processing of uranium ore, action of heat on carbonates; color test for phenols and aromatic amines; solvent properties of non-electrolytes; stereoscopic applications/methods; a valency balance;…

School Science Review, 1983

1983-01-01

257

Green Chemistry  

NSDL National Science Digital Library

This audio segment from PRI's The World Science Podcast explores the science of Green Chemistry. Hear about companies that are developing greener chemicals, and learn why they are fast becoming an attractive alternative for the multi-billion dollar chemical industry.

Foundation, Wgbh E.

2010-02-12

258

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents procedures, experiments, demonstrations, teaching suggestions, and information on a variety of chemistry topics including, for example, inert gases, light-induced reactions, calculators, identification of substituted acetophenones, the elements, analysis of copper minerals, extraction of metallic strontium, equilibrium, halogens, and…

School Science Review, 1982

1982-01-01

259

Chemistry Notes.  

ERIC Educational Resources Information Center

|Presents procedures, experiments, demonstrations, teaching suggestions, and information on a variety of chemistry topics including, for example, inert gases, light-induced reactions, calculators, identification of substituted acetophenones, the elements, analysis of copper minerals, extraction of metallic strontium, equilibrium, halogens, and…

School Science Review, 1982

1982-01-01

260

Chemistry's year  

NASA Astrophysics Data System (ADS)

The United Nations has proclaimed 2011 to be the International Year of Chemistry. Under this banner, chemists should seize the opportunity to highlight the rich history and successes of our subject to a much broader audience - and explain how it can help to solve the global challenges we face today and in the future.

2011-01-01

261

Chemistry Notes  

ERIC Educational Resources Information Center

|Describes several chemistry projects, including solubility, formula for magnesium oxide, dissociation of dinitrogen tetroxide, use of 1-chloro-2, 4-dinitrobenzene, migration of ions, heats of neutralizations, use of pocket calculators, sonic cleaning, oxidation states of manganese, and cell potentials. Includes an extract from Chemical Age on…

School Science Review, 1976

1976-01-01

262

Chlorine Chemistry  

NSDL National Science Digital Library

From poolcenter.com comes the Chlorine Chemistry Web site. Ten questions related to chlorine are answered such as What's the History of Chlorine, How Does Chlorine Work to Sanitize, and What Effect Does pH Have on Chlorine. Each is briefly explained in simple and non-technical language.

2008-01-25

263

Complex Chemistry on Interstellar Grains  

NASA Astrophysics Data System (ADS)

Early interstellar chemical models considered complex molecule formation on grains [Allen & Robinson (1977)], but current models assume that simple molecules form on grains and subsequent gas phase ion-molecule reactions produce the more complex species [Ruffle & Herbst (2001), Charnley (2001)]. It has been shown, however, that gas phase ion-molecule reactions are insufficient for the production of such complex organic species as ethanol (CH3CH2OH) and methyl formate (CH3OCHO) [Horn et al. (2004)]. Organics such as acetaldehyde (CH3CHO), ethanol, methyl formate, acetic acid (CH3COOH), and glycolaldehyde (CH2OHCHO) have also been detected in high abundance in regions of grain mantle disruption or evaporation, indicating that these species are formed on grain surfaces [see Chengalur & Kanekar (2003), Bottinelli et al. (2004), Hollis et al. (2001)]. The mechanisms for complex molecule production on grains are clearly much more important, and much more complex, than has been recognized. Recent observational studies of these types of species have offered insight into the mechanisms for their possible grain surface synthesis. The relative hot core abundances of the 2C structural isomers methyl formate, acetic acid, and glycolaldehyde (52:2:1, respectively [Hollis et al. (2001)]) indicate that if they form on grains it is not from kinetically-controlled single-atom addition reactions. Likewise, the 3C aldose sugar, glyceraldehyde (CH2OHCHOHCHO), was not detected in Sgr B2(N-LMH) [Hollis et al. (2004)] while the 3C ketose sugar, dihydroxyacetone (CO(CH2OH)2) was detected in this source [Widicus Weaver & Blake (2005)]. Chemical pathways favoring the more stable carbonates over acids and aldehydes are required to explain these results. Interestingly, all of these species can be formed from reactions involving the abundant grain mantle constituents CO, HCOOH, and CH3OH and their radical precursors. A model has been developed to investigate this type of chemical network, and the preliminary results of this model will be presented. The reactions incorporated into this model include photolysis of grain surface species, radical-radical combination reactions between photolysis products, aldehyde proton abstraction reactions, and radical recombination reactions between the photolysis products and aldehyde radicals. H addition reactions dominate the grain surface chemistry at low temperature, forming simple species such as water, methanol, and formaldehyde. Photolysis of simple grain mantle constituents leads to the production of surface radicals that can efficiently compete with H addition reactions at warmer temperatures, and so periodic thermal processing of grain mantles will lead to the buildup of more complex species such as formic acid, methyl formate, formamide, acetaldehyde, and glycolaldehyde. Aldehyde proton abstraction reactions can efficiently compete with single-atom addition reactions at both low and high temperatures, and so the mobile radicals can then react with the resultant aldehyde radicals to form more complex species. Simpler species will be favored at low temperature, but these radicals may also be stored in the grain mantle at low temperature and undergo more complex reactions upon grain mantle heating in hot core regions.

Widicus Weaver, Susanna L.; Kelley, Matthew J.; Blake, Geoffrey A.

264

Spectral Properties of Confined Atoms  

NASA Astrophysics Data System (ADS)

The changes in energy and photoionization spectra of atoms upon confinement by a spherical environment are explored theoretically. Two kinds of confinement are considered: an endohedral confinement, such as inside the bucky-ball C60, and an impenetrable spherical confinement of adjustable radius. We demonstrate modifications in the energy spectrum and electron correlation effects in confined atoms, the appearance, nature and origin of ``confinement'' resonances in photoionization spectra of such atoms, as well as new regularities in the periodic table for ``compressed'' atoms. These findings are of importance for basic and applied physics and chemistry of atoms, molecules, surfaces, etc.

Dolmatov, V. K.; Connerade, J. P.; Lakshmi, A. P.; Manson, S. T.

265

Transactinide nuclear chemistry at JAERI  

Microsoft Academic Search

The present status of transactinide nuclear chemistry research at JAERI (Japan Atomic Energy Research Institute) is reviewed.\\u000a Successful production of the transactinide nuclei, 261Rf and 262Db in the reactions of 248Cm(18O,5n) and 248Cm(19F,5n), respectively, at the JAERI tandem accelerator is reported. Aqueous chemistry of element 104, Rf, is being performed\\u000a with a newly developed rapid ion-exchange separation apparatus. Anion-exchange behaviour

Y. Nagame; H. Haba; K. Tsukada; M. Asai; K. Akiyama; M. Hirata; I. Nishinaka; S. Ichikawa; H. Nakahara; S. Goto; T. Kaneko; H. Kudo; A. Toyoshima; A. Shinohara; M. Schädel; J. V. Kratz; H. W. Gäggeler; A. Türler

2003-01-01

266

Interactive Teaching Units: Green Chemistry  

NSDL National Science Digital Library

As more and more organizations go "green", it makes sense that a number of educational institutions are participating as well. One such institution is the University of Glasgow which has developed this series of "green" chemistry teaching exercises known as Interactive Teaching units (ITUs). Currently, the site contains four ITU's, including "The Age of Refrigeration", "Titanium and the Titanium Dioxide Industry", and "The Atom Economy". The modules all draw on the concept of problem based learning to introduce key concepts of green chemistry and sustainability in an industrial context. All of these materials can be used in the college classroom in order to develop both teamwork and communication skills.

267

Chemistry Gateways and Resources  

NSDL National Science Digital Library

The Chemistry Gateways and Resources collection is comprised of chemistry-related web portals, web sites, and individual digital resources pertaining to many areas of the discipline - general chemistry, organic and inorganic chemistry, physical chemistry, and others - and intended for a wide range of audiences: educators and learners, the general public, and chemistry research communities.

2008-03-14

268

Resin Chemistry  

Microsoft Academic Search

\\u000a During the ensuing years since the last phenolic resins book was published, many new and remarkable developments have occurred\\u000a in the realm of phenolic chemistry and are given in this chapter.\\u000a \\u000a \\u000a A critical examination of the first step or addition step (methylolation) in the preparation of resoles is described and how\\u000a it can be controlled and compared with the typical

Louis Pilato

2010-01-01

269

The magnehydrogen in hadronic chemistry  

NASA Astrophysics Data System (ADS)

In this paper we have described in brief one of the great achievements accomplished by the Italian-American scientist Ruggero Maria Santilli [1], namely the isochemical model and magnehydrogen that form the subject matter of the hadronic Chemistry. This new chemical species of magnehydrogen consist of individual hydrogen atom bonded together and form stable clusters under a new internal attractive forces originating from the toroidal polarization of orbitals of atomic electrons when placed in strong magnetic fields. These magnecules are used as pollution free fuel and for other applications because there is no cracking involved while using the stored magnetic energy.

Zodape, Sangesh P.; Bhalekar, Anil A.

2013-10-01

270

Gumdrop Atoms  

NSDL National Science Digital Library

Students use gumdrops and toothpicks to make lithium atom models. Using these models, they investigate the makeup of atoms, including their relative size. Students also practice adding and subtracting electrons from an atom and determining the overall charges on atoms.

Integrated Teaching And Learning Program

271

Is click chemistry attractive for separation sciences?  

PubMed

Trends in LC focus on dedicated separation developments spanning different fields of applications ranging from sample preparation to miniaturization. Chromatographic performances result from the porous media, its implantation inside the "column," and its surface functionalization. Because molecular interactions govern chromatographic phenomena, surface functionalization is still a hot research topic. Besides standard approaches for surface functionalization, the use of new surface chemistry reactions opens new perspectives. Click chemistry belongs to this new class of chemical reactions, characterized by its specificity, compatibility with aqueous media, and high reaction yields. In this frame, we review the use of click chemistry reactions in chromatographic sciences. In a first part, we present click chemistry with a specific focus on its implementation in stationary phases. The use of these new clicked materials is detailed and discussed with respect to the chromatographic mode. PMID:23610023

Marechal, Audrey; El-Debs, Racha; Dugas, Vincent; Demesmay, Claire

2013-05-29

272

(Pesticide chemistry)  

SciTech Connect

This report summarizes a trip by L. W. Barnthouse of the Environmental Sciences Division (ESD), Oak Ridge National Laboratory (ORNL), to Hamburg, Federal Republic of Germany (FRG), where he participated in the 7th International Congress of Pesticide Chemistry. He chaired a workshop on experimental systems for determining effects of pesticides on nontarget organisms and gave an oral presentation at a symposium on pesticide risk assessment. Before returning to the United States, Dr. Barnthouse visited the Netherlands Institute for Sea Research in Texel, the Netherlands.

Barnthouse, L.W.

1990-09-04

273

Chemguide: Atomic Orbitals  

NSDL National Science Digital Library

This web page explains what atomic orbitals are in a way that makes it appropriate for pre-college introductory chemistry or physics courses. It goes into detail on s and p orbitals, including their shapes and energies, while devoting less discussion to d and f orbitals. The author uses an analogy comparing an atom to a multi-story house -- with the nucleus on the ground floor and then various rooms (orbitals) on the higher floors occupied by the electrons. A full page debunks the misconception that "orbitals" are like "orbits" (common among beginning students). Beyond this foundation, the tutorial explores how electrons fill orbitals (from low-to-high energy). It concludes with a set of questions, with answers provided, for self-gauging understanding. This page is part of Chemguide, an informational website developed by a veteran high school teacher to promote deeper understanding of concepts in introductory and intermediate-level chemistry.

Clark, Jim

2013-02-20

274

21 CFR 862.2850 - Atomic absorption spectrophotometer for clinical use.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Atomic absorption spectrophotometer for clinical...MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES...Instruments § 862.2850 Atomic absorption spectrophotometer for clinical...Identification. An atomic absorption spectrophotometer...

2010-04-01

275

21 CFR 862.2850 - Atomic absorption spectrophotometer for clinical use.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 false Atomic absorption spectrophotometer for clinical...MEDICAL DEVICES CLINICAL CHEMISTRY AND CLINICAL TOXICOLOGY DEVICES...Instruments § 862.2850 Atomic absorption spectrophotometer for clinical...Identification. An atomic absorption spectrophotometer...

2009-04-01

276

Industrial Chemistry and School Chemistry: Making chemistry studies more relevant  

Microsoft Academic Search

In this paper, we present the development and implementation over the period of more than 15 years of learning materials focusing on industrial chemistry as the main theme. The work was conducted in the Department of Science Teaching at the Weizmann Institute of Science, Israel. The project's general goal was to teach chemistry concepts in the context of industrial chemistry

Avi Hofstein; Miri Kesner

2006-01-01

277

FDA Hot Topics  

Center for Biologics Evaluation and Research (CBER)

Text VersionFDA Hot Topics. Alan E. Williams, Ph.D. ... January 27-29, 2010. FDA Hot topics. The Office of Blood Research and Review (OBRR), CBER. ... More results from www.fda.gov/downloads/biologicsbloodvaccines/newsevents

278

Hot Weather Tips  

MedlinePLUS

Home > Newsletters > Connections newsletter - Archives > Spring 2003 > HOT Weather Tips E-mail to a Friend Printable Version ©Family Caregiver Alliance We all suffer in hot weather. However, for elderly and disabled ...

279

Stationary Electron Atomic Model  

NASA Astrophysics Data System (ADS)

I will present a novel theory concerning the position and nature of the electron inside the atom. This new concept is consistant with present experimental evidence and adheres strictly to the valence-shell electron-pair repulsion (VSEPR) model presently used in chemistry for predicting the shapes of molecules and ions. In addition, I will discuss the atomic model concept as being a true harmonic oscillator, periodic motion at resonant frequency which produces radiation at discrete frequencies or line spectra is possible because the electron is under the action of two restoring forces, electrostatic attraction and superconducting respulsion of the electron's magnetic field by the nucleus.

Pressler, David E.

1998-04-01

280

Chemistry Notes.  

ERIC Educational Resources Information Center

|Presents laboratory procedures, classroom materials/activities, and demonstrations, including: vapor pressure of liquid mixtures and Raoult's law; preparation/analysis of transition metal complexes of ethylammonium chloride; atomic structure display using a ZX81 (includes complete program listing); "pop-up" models of molecules and ions; reactions…

School Science Review, 1982

1982-01-01

281

Chemistry Notes.  

ERIC Educational Resources Information Center

Presents laboratory procedures, classroom materials/activities, and demonstrations, including: vapor pressure of liquid mixtures and Raoult's law; preparation/analysis of transition metal complexes of ethylammonium chloride; atomic structure display using a ZX81 (includes complete program listing); "pop-up" models of molecules and ions; reactions…

School Science Review, 1982

1982-01-01

282

ITER hot cell  

Microsoft Academic Search

The paper provides an overview of the International Thermonuclear Experimental Reactor (ITER) hot cell system design. The system includes the hot cell proper, required for use both during machine assembly and operations, and the radwaste facility. The hot cell is divided in different areas and equipped with a variety of process and testing equipment. The components and waste streams are

O. Asuar; V. Baulo; T. Fisher; R. Haange; T. Honda; D. Maisonnier; D. Murdoch; C. Ozzano; J. Palmer; J. Sovka; T. Suzuki; A. Tesini; H. Yoshida

2003-01-01

283

Solar hot water heater  

Microsoft Academic Search

A solar hot water heater includes an insulated box having one or more hot water storage tanks contained inside and further having a lid which may be opened to permit solar radiation to heat a supply of water contained within the one or more hot water storage tanks. A heat-actuated control unit is mounted on an external portion of the

1982-01-01

284

Modelling Hot Air Balloons.  

ERIC Educational Resources Information Center

|A macroscopic way of modeling hot air balloons using a Newtonian approach is presented. Misleading examples using a car tire and the concept of hot air rising are discussed. Pressure gradient changes in the atmosphere are used to explain how hot air balloons work. (KR)|

Brimicombe, M. W.

1991-01-01

285

Atom-photon pair laser  

SciTech Connect

We study the quantum dynamics of an ultracold atomic gas trapped in an optical lattice within an optical high-Q resonator. The atoms are coherently illuminated with the cavity resonance tuned to a blue vibrational sideband so that stimulated gain of the resonator mode is accompanied by vibrational cooling of the atoms. This system exhibits a threshold above which pairwise stimulated generation of a cavity photon and an atom in the lowest vibrational band dominates spontaneous scattering and we find a combination of optical lasing with a buildup of a macroscopic population in the lowest lattice band. Including output coupling of ground-state atoms and replenishing of hot atoms into the cavity volume leads to a coherent, quantum correlated atom-photon pair source very analogous to twin light beam generation in a nondegenerate optical parametric oscillator.

Salzburger, Thomas; Ritsch, Helmut [Institute for Theoretical Physics, University of Innsbruck, Technikerstrasse 25/2, 6020 Innsbruck (Austria)

2007-06-15

286

Optical spectroscopy of trapped neutral atoms  

Microsoft Academic Search

Conclusions  An overview of optical spectroscopy on trapped atoms has been presented. The subject is a hot topics in the atomic physics\\u000a community and has also applications in other fields like nuclear physics. The advantages of a cold and dense atomic sample\\u000a in performing spectroscopy have been shown together with possible applications. New properties of atoms at ultralow temperatures\\u000a and new

C. Gabbanini

1997-01-01

287

Really Hot Stars  

NASA Astrophysics Data System (ADS)

Spectacular VLT Photos Unveil Mysterious Nebulae Summary Quite a few of the most beautiful objects in the Universe are still shrouded in mystery. Even though most of the nebulae of gas and dust in our vicinity are now rather well understood, there are some which continue to puzzle astronomers. This is the case of a small number of unusual nebulae that appear to be the subject of strong heating - in astronomical terminology, they present an amazingly "high degree of excitation". This is because they contain significant amounts of ions, i.e., atoms that have lost one or more of their electrons. Depending on the atoms involved and the number of electrons lost, this process bears witness to the strength of the radiation or to the impact of energetic particles. But what are the sources of that excitation? Could it be energetic stars or perhaps some kind of exotic objects inside these nebulae? How do these peculiar objects fit into the current picture of universal evolution? New observations of a number of such unusual nebulae have recently been obtained with the Very Large Telescope (VLT) at the ESO Paranal Observatory (Chile). In a dedicated search for the origin of their individual characteristics, a team of astronomers - mostly from the Institute of Astrophysics & Geophysics in Liège (Belgium) [1] - have secured the first detailed, highly revealing images of four highly ionized nebulae in the Magellanic Clouds, two small satellite galaxies of our home galaxy, the Milky Way, only a few hundred thousand light-years away. In three nebulae, they succeeded in identifying the sources of energetic radiation and to eludicate their exceptional properties: some of the hottest, most massive stars ever seen, some of which are double. With masses of more than 20 times that of the Sun and surface temperatures above 90 000 degrees, these stars are truly extreme. PR Photo 09a/03: Nebula around the hot star AB7 in the SMC. PR Photo 09b/03: Nebula near the hot Wolf-Rayet star BAT99-2 in the LMC. PR Photo 09c/03: Nebula near the hot binary star BAT99-49 in the LMC. PR Photo 09d/03: The N44C Nebula in the LMC. Four unique images of highly excited nebulae in the Magellanic Clouds ESO PR Photo 09a/03 ESO PR Photo 09a/03 [Preview - JPEG: 400 x 472 pix - 74k [Normal - JPEG: 800 x 943 pix - 720k] [Full-Res - JPEG: 1200 x 1414 pix - 1.2M] ESO PR Photo 09b/03 ESO PR Photo 09b/03 [Preview - JPEG: 400 x 466 pix - 70k [Normal - JPEG: 800 x 931 pix - 928k] [Full-Res - JPEG: 1200 x 1397 pix - 1.8M] ESO PR Photo 09c/03 ESO PR Photo 09c/03 [Preview - JPEG: 400 x 469 pix - 74k [Normal - JPEG: 800 x 937 pix - 1.1M] [Full-Res - JPEG: 1200 x 1405 pix - 2.2M] ESO PR Photo 09d/03 ESO PR Photo 09d/03 [Preview - JPEG: 400 x 473 pix - 28k [Normal - JPEG: 800 x 945 pix - 368k] [Full-Res - JPEG: 1200 x 1418 pix - 600k] Captions: PR Photo 09a/03 is a reproduction of a "near-true" three-colour composite image of the highly excited nebula around the hot double star AB7 in the Small Magellanic Cloud (SMC), obtained in January 2002 with the FORS1 multi-mode instrument at the 8.2-m VLT MELIPAL telescope at the Paranal Observatory (Chile). It is based on three exposures through narrow-band optical (interference) filters that isolate the light from specific atoms and ions. In this rendering, the blue colour represents the light from singly ionized Helium (He II; wavelength 468.6 nm; exposure time 30 min), green corresponds to doubly ionized oxygen ([O III]; 495.7 + 500.7 nm; 5 min) and red to hydrogen atoms (H; H-alpha line at 656.2 nm; 5 min). Of these three ions, He II is the tracer of high excitation, i.e. the bluest areas of the nebula are the hottest. The sky field measures 400 x 400 arcsec2; the original pixel size on the 2k x 2k CCD is 0.23 arcsec. North is up and east to the left. Before combination, the CCD frames were flat-fielded and cleaned of cosmic-rays. Moreover, the stars in the blue (He II) image were removed in order to provide a clearer view of the surrounding nebular emission. The reproduced brightness is proportional to the squar

2003-04-01

288

Environmental chemistry. Seventh edition  

SciTech Connect

This book presents a basic understanding of environmental chemistry and its applications. In addition to providing updated materials in this field, the book emphasizes the major concepts essential to the practice of environmental chemistry. Topics of discussion include the following: toxicological chemistry; toxicological chemistry of chemical substances; chemical analysis of water and wastewater; chemical analysis of wastes and solids; air and gas analysis; chemical analysis of biological materials and xenobiotics; fundamentals of chemistry; and fundamentals of organic chemistry.

Manahan, S.E. [Univ. of Missouri, Columbia, MO (United States)

1999-11-01

289

What is Chemistry?  

NSDL National Science Digital Library

Provided by Kiwi Web Chemistry & New Zealand, the "What is Chemistry?" Web site offers a wealth of chemistry information and links. Visitors can read the definition of and link to other sites on inorganic chemistry, organic chemistry, analytical chemistry, physical chemistry, stoichiometry, nuclear chemistry, alchemy, and biochemistry. Other pages of the site explore acids and bases, redox reductions, equations, moles, periodic tables, and more. This extensive and interesting site does a good job of clearly explaining some difficult concepts as well as providing educators and students a good source of other quality sites containing similar content.

Campbell, Allan

290

Rollback Atomicity  

Microsoft Academic Search

We introduce a new non-interference criterion for concurrent programs: rollback atomicity. Similarly to other definitions of atomicity, rollback atomicity of a given concurrent execution requires that there be a matching serial execution. Rollback atomicity differs from other definitions of atomicity in two key regards. First, it is formulated as a special case of view refinement. As such, it requires a

Serdar Tasiran; Tayfun Elmas

2007-01-01

291

DOE Fundamental Handbook: Chemistry. Volume 1 of 2.  

National Technical Information Service (NTIS)

The handbook includes information on the atomic structure of matter; chemical bonding; chemical equations; chemical interactions involved with corrosion processes; water chemistry control, including the principles of water treatment; the hazards of chemic...

1993-01-01

292

DOE Fundamentals Handbook: Chemistry. Volume 2 of 2.  

National Technical Information Service (NTIS)

The handbook includes information on the atomic structure of matter; chemical bonding; chemical equations; chemical interactions involved with corrosion processes; water chemistry control, including the principles of water treatment; the hazards of chemic...

1993-01-01

293

Development and Formative Evaluation of Computer Simulated College Chemistry Experiments.  

ERIC Educational Resources Information Center

This article describes the design, preparation, and initial evaluation of a set of computer-simulated chemistry experiments. The experiments entailed the use of an atomic emission spectroscope and a single-beam visible absorption spectrophometer. (Author/IRT)

Cavin, Claudia S.; Cavin, E. D.

1978-01-01

294

Elementary and brief introduction of hadronic chemistry  

NASA Astrophysics Data System (ADS)

The discipline, today known as Quantum Chemistry for atomic and subatomic level interactions has no doubt made a significant historical contributions to the society. Despite of its significant achievements, quantum chemistry is also known for its widespread denial of insufficiencies it inherits. An Italian-American Scientist Professor Ruggero Maria Santilli during his more than five decades of dedicated and sustained research has denounced the fact that quantum chemistry is mostly based on mere nomenclatures without any quantitative scientific contents. Professor R M Santilli first formulated the iso-, geno- and hyper-mathematics [1-4] that helped in understanding numerous diversified problems and removing inadequacies in most of the established and celebrated theories of 20th century physics and chemistry. This involves the isotopic, genotopic, etc. lifting of Lie algebra that generated Lie admissible mathematics to properly describe irreversible processes. The studies on Hadronic Mechanics in general and chemistry in particular based on Santilli's mathematics[3-5] for the first time has removed the very fundamental limitations of quantum chemistry [2, 6-8]. In the present discussion, we have briefly reviewed the conceptual foundations of Hadronic Chemistry that imparts the completeness to the Quantum Chemistry via an addition of effects at distances of the order of 1 fm (only) which are assumed to be Non-linear, Non-local, Non-potential, Non-hamiltonian and thus Non-unitary and its application in development of a new chemical species called Magnecules.

Tangde, Vijay M.

2013-10-01

295

Radiation Research: Chemistry and Physics.  

National Technical Information Service (NTIS)

Papers in this Proceedings are grouped under the following headings: (1) primary processes in radiation physics and chemistry; (2) radiation chemistry - general chemistry; (3) radiation chemistry - DNA and model systems; (4) radiation chemistry - other mo...

J. J. Broerse G. W. Barendsen H. B. Kal A. J. van der Kogel

1983-01-01

296

Using Games To Teach Chemistry: An Annotated Bibliography.  

ERIC Educational Resources Information Center

|Lists 67 published or marketed chemistry games organized under the following categories: (1) general knowledge; (2) elements and atomic structure; (3) nomenclature, formulas, and equation writing; (4) chemical reactions; (5) solutions and solubilities; (6) organic chemistry, and (8) miscellaneous subjects. Includes a brief description of each…

Russell, Jeanne V.

1999-01-01

297

Nuclear chemistry progress report  

SciTech Connect

This is the annual progress report for the Indiana University nuclear chemistry program for the 1992/1993 year. Accomplishments include the construction, testing, and initial experimental runs of the Indiana Silicon Sphere (ISiS) 4{pi} charged particle detector. ISiS is designed to study energy dissipation and multifragmentation phenomena in light-ion-induced nuclear reactions at medium-to-high energies. Its second test run was to examine 3.6 GeV {sup 3}He beam reactions at Laboratoire National Saturne (LNS) in Saclay. The development and deployment of this system has occupied a great deal of the groups effort this reporting period. Additional work includes: calculations of isotopic IMF yields in the {sup 4}He + {sup 116,124}Sn reaction; cross sections for A = 6 - 30 fragments from the {sup 4}He + {sup 28}Si reaction at 117 and 198 MeV; charging effects of passivated silicon detectors; neck emission of intermediate-mass fragments in the fission of hot heavy nuclei.

Viola, V.E.; Kwiatkowski, K.

1993-08-01

298

Interaction of hydrogen, methane, ethylene, and cyclopentane with hot tungsten: Implications for the growth of diamond films  

SciTech Connect

The production of hydrogen atoms from H[sub 2] was found to be largest on clean tungsten, less on carburized tungsten, and not observable on graphite. Evaporation of tungsten from carburized tungsten was seen at temperatures below 2500 [degree]C but not below 2200 [degree]C. XPS measurements indicated that slightly carburized tungsten contained some graphite in the surface region while heavily carburized tungsten contained much more graphite. The surface concentration of carbon was found to depend in a complicated manner on the balance between carbide and graphite growth and carbon evaporation. The reaction probability of the incident gas is also a determining factor. In addition, computer simulations were used to calculate the concentrations of various species in the gas phase under conditions which are typical of those used in diamond hot-filament CVD reactors. Calculated gas-phase species distributions near the substrate for carbon-atom/H[sub 2] mixtures are found to be similar for most species to those calculated for CH[sub 4]/H[sub 2] mixtures. It appears that the fast H[sub 2] and H chemistry determines the equilibrium mixture and that it is nearly independent of the type of carbon containing species introduced near the filament. Literature results obtained in typical diamond hot-filament CVD reactors are compared and interpreted on the basis of the present data.

Winters, H.F.; Seki, H. (IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, California 95120-6099 (United States)); Rye, R.R.; Coltrin, M.E. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States))

1994-07-15

299

Lower-Secondary Introductory Chemistry Course: A Novel Approach Based on Science-Education Theories, with Emphasis on the Macroscopic Approach, and the Delayed Meaningful Teaching of the Concepts of Molecule and Atom  

ERIC Educational Resources Information Center

|We present a programme for a novel introductory lower-secondary chemistry course (seventh or eighth grade) that aims at the application of theories of science education, and in particular of conceptual/meaningful learning and of teaching methodology that encourages active and inquiry forms of learning The approach is rigorous with careful use of…

Tsaparlis, Georgios; Kolioulis, Dimitrios; Pappa, Eleni

2010-01-01

300

ACS Green Chemistry Institute  

NSDL National Science Digital Library

This special feature page from the American Chemical Society (ACS) showcases the up-and-coming field of "green chemistry," that is, the development of chemical products and processes that eliminate or reduce the use and generation of hazardous substances. A list of principles behind green chemistry, a searchable bibliography of green chemistry references, and green chemistry links (including conferences). This page comes from ACS's Green Chemistry Project, a three-year educational project to develop and disseminate green chemistry educational materials for graduate and undergraduate chemistry students.

2005-12-13

301

Reviews Book: Sustainable Energy—Without the Hot Air Equipment: Doppler Effect Unit Book: The Physics of Rugby Book: Plastic Fantastic: How the Biggest Fraud in Physics Shook the Scientific World Equipment: Brunel Eyecam Equipment: 200x Digital Microscope Book: The Atom and the Apple: Twelve Tales from Contemporary Physics Book: Physics 2 for OCR Web Watch  

NASA Astrophysics Data System (ADS)

WE RECOMMEND Sustainable Energy—Without the Hot Air This excellent book makes sense of energy facts and figures Doppler Effect Unit Another simple, effective piece of kit from SEP Plastic Fantastic: How the Biggest Fraud in Physics Shook the Scientific World Intriguing and unique write-up of an intellectual fraud case Brunel Eyecam An affordable digital eyepiece for your microscope 200x Digital Microscope An adjustable digital flexcam for classroom use The Atom and the Apple: Twelve Tales from Contemporary Physics A fascinating round-up of the recent history of physics WORTH A LOOK The Physics of Rugby Book uses sport analogy and context to teach physics concepts Physics 2 for OCR Essential textbook for the course but otherwise pointless WEB WATCH Some free teaching materials are better than those you'd pay for

2009-09-01

302

Hot-wire anemometry  

Microsoft Academic Search

A brief historical survey of hot-wire anemometry is presented and questions of hot-wire response are investigated, taking into account sensor properties, steady-heat-loss laws, the dynamic response of the wires, the sensitivity coefficients of the wires, the characteristics of a wire of finite length, the spatial resolution of hot wires, and the aerodynamic perturbations of the probes. A description of electronic

G. Comte-Bellot

1976-01-01

303

HotBot  

NSDL National Science Digital Library

HotBot, a service of HotWired Ventures, uses the Inktomi search engine as the heart of its new Internet search service. It claims to index the full text contents of 50 million Web pages, as well as Usenet news and mailing lists. This would make it the largest search engine on the Internet. HotBot supports Boolean AND/OR/NOT, and phrase searching. It provides relevance feedback with retrieval. It also supports chronological, domain, and geographic searches, as well as media type searches such as Java, VRML, and Acrobat. HotBot is a public "beta" site and encourages feedback and bug reports.

304

Mechanisms influencing {open_quotes}hot-wire{close_quotes} deposition of hydrogenated amorphous silicon  

SciTech Connect

Intrinsic hydrogenated amorphous silicon (a-Si:H) has been deposited using a hot tungsten filament in pure silane to drive the deposition chemistry{emdash}the {open_quotes}hot-wire{close_quotes} deposition method. The electronic and infrared properties of the film have been measured as a function of deposition parameters, leading to three principal conclusions. First, to obtain a high quality material, the Si atoms evaporated from the filament (distance L from the substrate) must react with silane (density n{sub s}) before reaching the substrate; this requires n{sub s}L greater than a critical value. Second, radical-radical reactions cause deterioration of film properties at high values of G(n{sub s}L),{sup 3} where G is the film growth rate; this requires G(n{sub s}L){sup 3} less than a critical value. Finally, the film quality is a function of G, and as G is increased the substrate temperature must be correspondingly increased to obtain high film quality. By optimizing these parameters, we have produced films with excellent electronic properties (e.g., ambipolar diffusion length {gt}200 nm) at {gt}5 nm/s deposition rate. Based on these insights, formulas are also given for optimizing film properties in multiple-filament geometries and in diluted silane. {copyright} {ital 1997 American Institute of Physics.}

Molenbroek, E.C.; Mahan, A.H. [National Renewable Energy Laboratory, Golden, Colorado 80401 (United States); Gallagher, A. [JILA, University of Colorado and National Institute of Standards and Technology, Boulder, Colorado 80309-0440 (United States)

1997-08-01

305

Supramolecular chemistry: Functional structures on the mesoscale  

Microsoft Academic Search

F or over 100 years, chemistry has focused primarily on un- derstanding the behavior of molecules and their construction from constituent atoms. Our current level of understanding of molecules and chemical construction techniques has given us the confidence to tackle the construction of virtually any molecule, be it biological or designed, organic or inorganic, monomeric or macromolecular in origin. During

SonBinh T. Nguyen; Douglas L. Gin; Joseph T. Hupp; Xi Zhang

2001-01-01

306

Index to the Understanding the Atom Series.  

ERIC Educational Resources Information Center

|This index was prepared for the set of 51 booklets in the "Understanding the Atom Series" published by the U. S. Atomic Energy Commission for high school students and their teachers. In addition to the index, a complete list of the series is provided in which the booklets are grouped into the categories of physics, chemistry, biology, nuclear…

Atomic Energy Commission, Oak Ridge, TN. Div. of Technical Information.

307

Digital Resource Package for Teaching Atomic Structure  

NSDL National Science Digital Library

This digital resource package is a collection of online sources to help K-12 teachers create lessons on the Chemistry subject of atomic structures. Topics include The History of the Atom, Reference Material, Tutorials, Simulations, Questions and Activities, Periodic Tables, and resources for more advanced learners.

Moin, Laura

308

Index to the Understanding the Atom Series.  

ERIC Educational Resources Information Center

This index was prepared for the set of 51 booklets in the "Understanding the Atom Series" published by the U. S. Atomic Energy Commission for high school students and their teachers. In addition to the index, a complete list of the series is provided in which the booklets are grouped into the categories of physics, chemistry, biology, nuclear…

Atomic Energy Commission, Oak Ridge, TN. Div. of Technical Information.

309

Is There an Irreducible Chemistry Core? A Shot from a Canonical Cannon.  

ERIC Educational Resources Information Center

|Argues for including several key ideas in every introductory general chemistry course, including the phenomena of chemistry, the organization and classification of matter, atomic structure, molecular bonding and molecular structure, the language of chemistry, the mole, chemical reactions and reactivity, chemical kinetics, chemical equilibrium,…

Schwartz, A. Truman

1999-01-01

310

Effect of Hot Rolling Process on Microstructure and Properties of Low-Carbon Al-Killed Steels Produced Through TSCR Technology  

Microsoft Academic Search

Low-carbon Al-killed hot rolled strips for direct forming, cold rolling, and galvanizing applications are produced from the similar chemistry at Ezz Flat Steel (EFS) through thin slab casting and rolling (TSCR) technology. The desired mechanical and microstructural properties in hot bands for different applications are achieved through control of hot rolling parameters, which in turn control the precipitation and growth

S. K. Paul; U. Ahmed; G. M. Megahed

2010-01-01

311

Effect of Hot Rolling Process on Microstructure and Properties of Low-Carbon Al-Killed Steels Produced Through TSCR Technology  

Microsoft Academic Search

Low-carbon Al-killed hot rolled strips for direct forming, cold rolling, and galvanizing applications are produced from the similar chemistry at Ezz Flat Steel (EFS) through thin slab casting and rolling (TSCR) technology. The desired mechanical and microstructural properties in hot bands for different applications are achieved through control of hot rolling parameters, which in turn control the precipitation and growth

S. K. Paul; U. Ahmed; G. M. Megahed

2011-01-01

312

Preliminary geothermal investigations at Manley Hot Springs, Alaska  

SciTech Connect

Manley Hot Springs is one of several hot springs which form a belt extending from the Seward Peninsula to east-central Alaska. All of the hot springs are low-temperature, water-dominated geothermal systems, having formed as the result of circulation of meteoric water along deepseated fractures near or within granitic intrusives. Shallow, thermally disturbed ground at Manley Hot Springs constitutes an area of 1.2 km by 0.6 km along the lower slopes of Bean Ridge on the north side of the Tanana Valley. This area includes 32 springs and seeps and one warm (29.1/sup 0/C) well. The hottest springs range in temperature from 61/sup 0/ to 47/sup 0/C and are presently utilized for space heating and irrigation. This study was designed to characterize the geothermal system present at Manley Hot Springs and delineate likely sites for geothermal drilling. Several surveys were conducted over a grid system which included shallow ground temperature, helium soil gas, mercury soil and resistivity surveys. In addition, a reconnaissance ground temperature survey and water chemistry sampling program was undertaken. The preliminary results, including some preliminary water chemistry, show that shallow hydrothermal activity can be delineated by many of the surveys. Three localities are targeted as likely geothermal well sites, and a model is proposed for the geothermal system at Manley Hot Springs.

East, J.

1982-04-01

313

Atomic Orbitals  

NSDL National Science Digital Library

The Atomic Orbitals website is a distribution point for the orbital image generating program "Orbital Viewer" as well as the home of a collection of images generated with the program. Atomic and molecular orbitals are constructed. For atoms, the hydrogenic solution, up to n=30, is generated and for molecules the linear combination of atomic orbitals method is used.

Manthey, David

2009-03-24

314

Atomic Structure  

NSDL National Science Digital Library

In this activity students explore the structure and properties of atoms. They construct models of atoms with properties of particular mass and charge; create models of atoms with different stabilities by adding or subtracting neutrons, protons, and electrons to a model atom; and determine that the same element may have varying number of neutrons and these form isotopes.Students will be able to:

Consortium, The C.

2011-12-11

315

The Earth's Hot Spots.  

ERIC Educational Resources Information Center

Hot spots are isolated areas of geologic activity where volcanic eruptions, earthquakes, and upwelling currents occur far from plate boundaries. These mantle plumes are relatively stable and crustal plates drift over them. The nature and location of hot spots (with particular attention to the Hawaiian Islands and Iceland) are discussed. (DH)

Vink, Gregory E.; And Others

1985-01-01

316

Household hot water systems  

Microsoft Academic Search

An arrangement for combination with the conventional hot water system of a house or building in which the water is conventionally heated and stored in a tank, the arrangement comprising a solar energy panel (at an upper level) with a thermostatic valve and a supplementary cold water tank, connected into the system in such a way that hot water is

Tacchi

1983-01-01

317

Solar hot water generator  

Microsoft Academic Search

A solar hot water generating system is disclosed which comprises a vertically pivotable heat exchanger automatically pivotable by means of a timer-actuated electric motor. The heat exchanger is fluidly connected to an insulated storage tank which retains the thermal values of the heated fluid. The system is adapted to provide hot water for domestic and industrial uses, such as heating,

1982-01-01

318

Hot air solar engine  

Microsoft Academic Search

A hot air solar engine has two heat engines at opposing ends of a common piston assembly to provide alternate cooperative expansion and compression action. Each of the heat engines has a compressor and an expander wherein a single dual-diameter piston head serves as the piston portion of each. The hot air solar engine further includes a solar collector having

1983-01-01

319

Multipurpose Reprocessing Hot Cell.  

National Technical Information Service (NTIS)

A multipurpose hot cell for use in the new head end system is described. The use of a hot cell as part of the routine fuel charging procedure provides considerable flexibility in handling a wide variety of fuel sizes up to 25,000 lb.

R. D. Fletcher

1975-01-01

320

Hot corrosion of materials: Fundamental studies  

NASA Astrophysics Data System (ADS)

Hot corrosion is the accelerated oxidation of materials at elevated temperatures induced by a thin film of fused salt deposit. Because of its high thermodynamic stability in the mutual presence of sodium and sulfur impurities in an oxidizing gas, Na2SO4 is often found to be the dominant salt in the deposit. The corrosive oxyanion-fused salts are usually ionically conducting electrolytes that exhibit an acid/base chemistry, so that hot corrosion must occur by an electrochemical mechanism that may involve fluxing of the protective oxides. With the aid of high-temperature reference electrodes to quantify an acid/base scale, the solubilities for various metal oxides in fused Na2SO4 have been measured, and these show remarkable agreement with the theoretical expectations from the thermodynamic phase stability diagrams for the relevant Na-Metal-S-O systems. The solubilities of several oxides infused Na2SO4-NaVO3 salt solutions have also been measured and modeled. Such information is important both in evaluating the corrosion resistance of materials and in interpreting any oxide fluxing/reprecipitation mechanisms. Various electrochemical measurements have identified the S2O7 2- anion (dissolved SO3) as the oxidant that is reduced in the hot corrosion process. Electrochemical polarization studies have elucidated the corrosion reactions and clarified the corrosion kinetics of alloys. Mechanistic models for Type I and Type II hot corrosion are discussed briefly.

Rapp, Robert A.; Zhang, Yun-Shu

1994-12-01

321

Using Games To Teach Chemistry: An Annotated Bibliography  

NASA Astrophysics Data System (ADS)

A list of published or marketed games based on a chemistry motif is presented. Each game is listed according to its level, subject matter, and title. A bibliographic notation and a short description are given for each game. For Introductory/High School/General Chemistry, 45 games are listed under the subjects General Knowledge; Elements & Atomic Structure (not Symbols); Nomenclature, Formulas, & Equation Writing; Chemical Reactions: Solutions & Solubilities; and Other Subjects. Seventeen games are listed under Organic Chemistry and 4 games under Other Chemistry Games. Computer games designed for outdated computers (PDP-11, TRS-80, and Apple II) are not included.

Russell, Jeanne V.

1999-04-01

322

Advancing manufacturing through computational chemistry  

SciTech Connect

The capabilities of nanotechnology and computational chemistry are reaching a point of convergence. New computer hardware and novel computational methods have created opportunities to test proposed nanometer-scale devices, investigate molecular manufacturing and model and predict properties of new materials. Experimental methods are also beginning to provide new capabilities that make the possibility of manufacturing various devices with atomic precision tangible. In this paper, we will discuss some of the novel computational methods we have used in molecular dynamics simulations of polymer processes, neural network predictions of new materials, and simulations of proposed nano-bearings and fluid dynamics in nano- sized devices.

Noid, D.W.; Sumpter, B.G.; Tuzun, R.E.

1995-12-31

323

Accurate theoretical chemistry with coupled pair models.  

PubMed

Quantum chemistry has found its way into the everyday work of many experimental chemists. Calculations can predict the outcome of chemical reactions, afford insight into reaction mechanisms, and be used to interpret structure and bonding in molecules. Thus, contemporary theory offers tremendous opportunities in experimental chemical research. However, even with present-day computers and algorithms, we cannot solve the many particle Schrodinger equation exactly; inevitably some error is introduced in approximating the solutions of this equation. Thus, the accuracy of quantum chemical calculations is of critical importance. The affordable accuracy depends on molecular size and particularly on the total number of atoms: for orientation, ethanol has 9 atoms, aspirin 21 atoms, morphine 40 atoms, sildenafil 63 atoms, paclitaxel 113 atoms, insulin nearly 800 atoms, and quaternary hemoglobin almost 12,000 atoms. Currently, molecules with up to approximately 10 atoms can be very accurately studied by coupled cluster (CC) theory, approximately 100 atoms with second-order Møller-Plesset perturbation theory (MP2), approximately 1000 atoms with density functional theory (DFT), and beyond that number with semiempirical quantum chemistry and force-field methods. The overwhelming majority of present-day calculations in the 100-atom range use DFT. Although these methods have been very successful in quantum chemistry, they do not offer a well-defined hierarchy of calculations that allows one to systematically converge to the correct answer. Recently a number of rather spectacular failures of DFT methods have been found-even for seemingly simple systems such as hydrocarbons, fueling renewed interest in wave function-based methods that incorporate the relevant physics of electron correlation in a more systematic way. Thus, it would be highly desirable to fill the gap between 10 and 100 atoms with highly correlated ab initio methods. We have found that one of the earliest (and now almost forgotten) of this class of methods, the coupled-electron pair approximation (CEPA), performs exceedingly well in chemical applications. In this Account, we examine the performance of CEPA in chemical applications. One attractive feature of CEPA, in addition to its surprising accuracy that surpasses that of DFT and MP2 theory, is a simplicity that allows for straightforward and very efficient approximations and extensions to be developed; these are much more difficult or even impossible with the more rigorous CC theory. Thus, approximate CEPA methods can be implemented efficiently enough to allow for calculations on molecules of 50-100 atoms, perhaps the most common range in contemporary chemical research. PMID:19296607

Neese, Frank; Hansen, Andreas; Wennmohs, Frank; Grimme, Stefan

2009-05-19

324

What Is Hot Yoga (Bikram)?  

MedlinePLUS

... reprinted for personal, noncommercial use only. What is hot yoga? By Mayo Clinic staff Original Article: http:// ... e-mail address Sign up Question What is hot yoga? What’s different about hot yoga versus other ...

325

Constitutional dynamic chemistry: bridge from supramolecular chemistry to adaptive chemistry.  

PubMed

Supramolecular chemistry aims at implementing highly complex chemical systems from molecular components held together by non-covalent intermolecular forces and effecting molecular recognition, catalysis and transport processes. A further step consists in the investigation of chemical systems undergoing self-organization, i.e. systems capable of spontaneously generating well-defined functional supramolecular architectures by self-assembly from their components, thus behaving as programmed chemical systems. Supramolecular chemistry is intrinsically a dynamic chemistry in view of the lability of the interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their constituents. The same holds for molecular chemistry when the molecular entity contains covalent bonds that may form and break reversibility, so as to allow a continuous change in constitution by reorganization and exchange of building blocks. These features define a Constitutional Dynamic Chemistry (CDC) on both the molecular and supramolecular levels.CDC introduces a paradigm shift with respect to constitutionally static chemistry. The latter relies on design for the generation of a target entity, whereas CDC takes advantage of dynamic diversity to allow variation and selection. The implementation of selection in chemistry introduces a fundamental change in outlook. Whereas self-organization by design strives to achieve full control over the output molecular or supramolecular entity by explicit programming, self-organization with selection operates on dynamic constitutional diversity in response to either internal or external factors to achieve adaptation.The merging of the features: -information and programmability, -dynamics and reversibility, -constitution and structural diversity, points to the emergence of adaptive and evolutive chemistry, towards a chemistry of complex matter. PMID:22169958

Lehn, Jean-Marie

2012-01-01

326

The role of organic haze in Titan's atmospheric chemistry  

Microsoft Academic Search

One of the key components controlling the chemical composition and climatology of Titan's atmosphere is the removal of reactive atomic hydrogen from the atmosphere. A proposed process of the removal of atomic hydrogen is the heterogeneous reaction with organic aerosol. In this study, we investigate the effect of heterogeneous reactions in Titan's atmospheric chemistry using new measurements of the heterogeneous

Yasuhito Sekine; Sébastien Lebonnois; Hiroshi Imanaka; Takafumi Matsui; Emma L. O. Bakes; Christopher P. McKay; Bishun N. Khare; Seiji Sugita

2008-01-01

327

Collaborative Physical Chemistry Projects Involving Computational Chemistry  

Microsoft Academic Search

The physical chemistry classes from three colleges have collaborated on two computational chemistry projects using Quantum CAChe 3.0 and Gaussian 94W running on Pentium II PCs. Online communication by email and the World Wide Web was an important part of the collaboration. In the first project, students used molecular modeling to predict benzene derivatives that might be possible hair dyes.

David M. Whisnant; Jerry J. Howe; Lisa S. Lever

2000-01-01

328

Chemistry with Inexpensive Materials: Spray Bottles and Plastic Bags.  

ERIC Educational Resources Information Center

Presents eight chemistry activities that are interesting and involve simple, easily available materials. Topics include mystery writing, valentine hearts, flame tests, evaporation race, buoyancy versus mass, determination of relative masses of gases, mole sample container, and cold and hot packs. (DDR)

Zoltewicz, Susan

1993-01-01

329

Chemistry with Inexpensive Materials: Spray Bottles and Plastic Bags.  

ERIC Educational Resources Information Center

|Presents eight chemistry activities that are interesting and involve simple, easily available materials. Topics include mystery writing, valentine hearts, flame tests, evaporation race, buoyancy versus mass, determination of relative masses of gases, mole sample container, and cold and hot packs. (DDR)|

Zoltewicz, Susan

1993-01-01

330

Special Report: Brain Chemistry.  

ERIC Educational Resources Information Center

Chemical actions in the brain result in cognitive, emotional, neuroendocrine, neuromuscular, and/or neurocirculatory effects. Developments in understanding brain chemistry are discussed, considering among others, neurotransmitter chemistry, neuropeptides, drugs and the brain, antidepressants, and actions of minor tranquilizers. (JN)

Krassner, Michael B.

1983-01-01

331

Environmental chemistry: Volume A  

SciTech Connect

This is an extensive introduction to environmental chemistry for engineering and chemical professionals. The contents of Volume A include a brief review of basic chemistry prior to coverage of litho, atmo, hydro, pedo, and biospheres.

Yen, T.F.

1999-08-01

332

Chemistry of hot springs along the Eastern Lau Spreading Center  

Microsoft Academic Search

The Eastern Lau Spreading Center (ELSC) is the southernmost part of the back-arc spreading axis in the Lau Basin, west of the Tonga trench and the active Tofua volcanic arc. Over its 397-km length it exhibits large and systematic changes in spreading rate, magmatic\\/tectonic processes, and proximity to the volcanic arc. In 2005, we collected 81 samples of vent water

Michael J. Mottl; Jeffrey S. Seewald; C. Geoffrey Wheat; Margaret K. Tivey; Peter J. Michael; Giora Proskurowski; Thomas M. McCollom; Eoghan Reeves; Jessica Sharkey; C.-F. You; L.-H. Chan; Thomas Pichler

2011-01-01

333

Chemistry of hot springs on the Mid-Atlantic Ridge  

Microsoft Academic Search

The first hydrothermal fluid samples collected along the slow-spreading Mid-Atlantic Ridge (MAR) are remarkably similar in composition and temperature to fluids collected along the shallower, faster-spreading East Pacific Rise (EPR). The MAR fluids, like those from the EPR, appear to be in equilibrium with a greenschist-facies mineral assemblage. In contrast to the EPR, the more fractured nature of the MAR

A. C. Campbell; M. R. Palmer; G. P. Klinkhammer; T. S. Bowers; J. M. Edmond; J. R. Lawrence; J. F. Casey; G. Thompson; S. Humphris; P. Rona; J. A. Karson

1988-01-01

334

Aquatic Chemistry, Third Edition  

NASA Astrophysics Data System (ADS)

Most water scientists and environmental engineers will recognize this classic environmental chemistry text as “Stumm and Morgan” rather than Aquatic Chemistry. Publication of the first edition in 1970 established a standard for books dealing with environmental chemistry in terms of depth and breadth of coverage. Scientists and engineers concerned with issues of water quality are well advised to have Aquatic Chemistry as part of their personal libraries, or at least in their office libraries.

Schroeder, Edward D.; Young, Thomas M.

335

CSA Hot Topics Series  

NSDL National Science Digital Library

The Hot Topics series provides a free sampling of the resources in Cambridge Scientific Abstracts (CSA) and the Internet Database Service (IDS). The 30 topics span subjects in the humanities, engineering, environmental policy, and medicine. Each Hot Topic gives an overview of the subject, key citations with abstracts, a list of Websites, a glossary, a comment form so that users can correspond with the editors, and a "source" section, which explains from which of CSA's paid services the resources were culled. The latest hot topic is MicroElectroMechanical systems (MEMS), "small integrated devices or systems that combine electrical and mechanical components."

336

The graphite furnace and its role in atomic spectroscopy  

Microsoft Academic Search

The diversity of applications of the graphite furnace is extraordinary, encompassing the fields of physics, thermochemistry, spectroscopy and analytical chemistry. In this respect, the graphite furnace has been used on a continuous basis as a research tool for nearly a century. Following its introduction as an atomization source for atomic absorption spectrometry by Lvov in 1959, its role in atomic

R. E. Sturgeon

1996-01-01

337

Mechanisms in Photographic Chemistry  

ERIC Educational Resources Information Center

Reviews current research interests in photographic chemistry, involving two proposed models for spectral sensitization of crystal defects and impurities in the photolysis reactivity and the mechanisms of development and complexation. Establishment of photographic chemistry in a chemistry curriculum is recommended. (CC)

Sahyun, M. R. V.

1974-01-01

338

Green Chemistry and Education.  

ERIC Educational Resources Information Center

|Many students today are profoundly interested in the sustainability of their world. Introduces Green Chemistry and its principles with teaching materials. Green Chemistry is the use of chemistry for pollution prevention and the design of chemical products and processes that are environmentally benign. (ASK)|

Hjeresen, Dennis L.; Schutt, David L.; Boese, Janet M.

2000-01-01

339

Green Chemistry and Education.  

ERIC Educational Resources Information Center

Many students today are profoundly interested in the sustainability of their world. Introduces Green Chemistry and its principles with teaching materials. Green Chemistry is the use of chemistry for pollution prevention and the design of chemical products and processes that are environmentally benign. (ASK)

Hjeresen, Dennis L.; Schutt, David L.; Boese, Janet M.

2000-01-01

340

Mechanisms in Photographic Chemistry  

ERIC Educational Resources Information Center

|Reviews current research interests in photographic chemistry, involving two proposed models for spectral sensitization of crystal defects and impurities in the photolysis reactivity and the mechanisms of development and complexation. Establishment of photographic chemistry in a chemistry curriculum is recommended. (CC)|

Sahyun, M. R. V.

1974-01-01

341

Aquatic Chemistry, Third Edition  

Microsoft Academic Search

Most water scientists and environmental engineers will recognize this classic environmental chemistry text as ``Stumm and Morgan'' rather than Aquatic Chemistry. Publication of the first edition in 1970 established a standard for books dealing with environmental chemistry in terms of depth and breadth of coverage. Scientists and engineers concerned with issues of water quality are well advised to have Aquatic

Edward D. Schroeder; Thomas M. Young

1996-01-01

342

Analytical chemistry instrumentation  

Microsoft Academic Search

Separate abstracts were prepared for 48 papers in these conference proceedings. The topics covered include: analytical chemistry and the environment; environmental radiochemistry; automated instrumentation; advances in analytical mass spectrometry; Fourier transform spectroscopy; analytical chemistry of plutonium; nuclear analytical chemistry; chemometrics; and nuclear fuel technology. (LEW)

Laing

1986-01-01

343

Atomic Interactions  

NSDL National Science Digital Library

Explore the interactions between various combinations of two atoms. Turn on the force arrows to see either the total force acting on the atoms or the individual attractive and repulsive forces. Try the "Adjustable Attraction" atom to see how changing the parameters affects the interaction.

Simulations, Phet I.; Adams, Wendy; Blanco, John; Perkins, Kathy; Podolefsky, Noah; Wieman, Carl

2009-08-01

344

The Dawn of Chemistry  

NASA Astrophysics Data System (ADS)

Within the precise cosmological framework provided by the ?-cold dark matter model and standard Big Bang nucleosynthesis, the chemical evolution of the pregalactic gas can now be followed with accuracy limited only by the uncertainties on the reaction rates. Starting during the recombination era, the formation of the first molecules and molecular ions containing hydrogen, deuterium, helium, and lithium was severely hindered by the low density of the expanding Universe, the intensity of the cosmic radiation field, and the absence of solid catalyzers. Molecular hydrogen and deuterated hydrogen, the most abundant species formed in the gas phase prior to structure formation, played a fundamental role in the cooling of the gas clouds that gave birth to the first stellar generation, contributing to determine the scale of fragmentation. Primordial molecules also interacted with the photons of the cosmic background via resonant scattering, absorption, and emission. In this review, we examine the current status of the chemistry of the early Universe and discuss the most relevant reactions for which uncertainties still exist from theory or laboratory experiments. The prospects for detecting spectral distortions or spatial anisotropies due to the first atoms and molecules are also addressed.

Galli, Daniele; Palla, Francesco

2013-08-01

345

Cometary MHD and chemistry  

NASA Astrophysics Data System (ADS)

An MHD and chemical comet-coma model was developed, applying the computer program of Huebner (1985) for the detailed chemical evolution of a spherically expanding coma and the program of Schmidt and Wegman (1982) and Wegman (1987) for the MHD flow of plasma and magnetic field in a comet to the Giotto-mission data on the ion abundances measured by the HIS ion mass spectrometer. The physics and chemistry of the coma are modeled in great detail, including photoprocesses, gas-phase chemical kinetics, energy balance with a separate electron temperature, multifluid hydrodynamics with a transition to free molecular flow, fast-streaming atomic and molecular hydrogen, counter and cross streaming of the ionized species relative to the neutral species in the coma-solar wind interaction region with momentum exchange by elastic collisions, mass-loading through ion pick-up, and Lorentz forces of the advected magnetic field. The results, both inside and outside of the contact surface, are discussed and compared with the relevant HIS ion mass spectra.

Wegmann, R.; Schmidt, H. U.; Huebner, W. F.; Boice, D. C.

1987-11-01

346

Exploring Conceptual Frameworks of Models of Atomic Structures and Periodic Variations, Chemical Bonding, and Molecular Shape and Polarity: A Comparison of Undergraduate General Chemistry Students with High and Low Levels of Content Knowledge  

ERIC Educational Resources Information Center

The purpose of the study was to explore students' conceptual frameworks of models of atomic structure and periodic variations, chemical bonding, and molecular shape and polarity, and how these conceptual frameworks influence their quality of explanations and ability to shift among chemical representations. This study employed a purposeful sampling…

Wang, Chia-Yu; Barrow, Lloyd H.

2013-01-01

347

Exploring Conceptual Frameworks of Models of Atomic Structures and Periodic Variations, Chemical Bonding, and Molecular Shape and Polarity: A Comparison of Undergraduate General Chemistry Students with High and Low Levels of Content Knowledge  

ERIC Educational Resources Information Center

|The purpose of the study was to explore students' conceptual frameworks of models of atomic structure and periodic variations, chemical bonding, and molecular shape and polarity, and how these conceptual frameworks influence their quality of explanations and ability to shift among chemical representations. This study employed a purposeful…

Wang, Chia-Yu; Barrow, Lloyd H.

2013-01-01

348

Jupiter's Hot Spots  

NASA Video Gallery

NASA postdoctoral fellow David Choi discusses his study of dark features in Jupiter's atmosphere called "hot spots," and their connection to large-scale atmospheric waves. › Download video in HD formats       › Related story

gsfcvideo

2013-03-13

349

Hot Dry Rock Technology.  

National Technical Information Service (NTIS)

This session at the Geothermal Energy Program Review X: Geothermal Energy and the Utility Market consisted of four presentations: 'Hot Dry Rock - Summary' by George P. Tennyson, Jr.; 'HDR Opportunities and Challenges Beyond the Long Term Flow Test' by Dav...

2005-01-01

350

Hot off the Press.  

PubMed

A personal selection of 32 recent papers is presented covering various aspects of current developments in bioorganic chemistry and novel natural products such as volvalerenol from Valeriana hardwickii. PMID:24056886

Hill, Robert A; Sutherland, Andrew

2013-09-11

351

New Trends in Chemistry Teaching. Volume V. The Teaching of Basic Sciences: Chemistry.  

ERIC Educational Resources Information Center

|This collection of articles, originally published in national and international journals, is fifth in a series devoted to trends in teaching chemistry. The volume is divided into nine sections, each with an introduction explaining why papers have been selected and outlining their particular interest. Section I provides a list of atomic masses,…

United Nations Educational, Scientific, and Cultural Organization, Paris (France).

352

The Hot Tub Mystery  

NSDL National Science Digital Library

This case study sets up a mystery and asks students to solve it using science: why was the couple found dead in their hot tub? The material asks students to connect seemingly unrelated factors, such as blood pressure, hot water and alcohol. The material would be most appropriate for lower level undergraduate students. The case study and teaching notes may be downloaded in PDF format. The site also includes a section for instructor feedback where general comments may be read and contributed.

House, Herbert

2011-01-06

353

Alcohol, Chemistry and You  

NSDL National Science Digital Library

Developed by Kennesaw State University, ChemCases.com is a series of curriculum units that link responsible decision making in product development with chemical principles taught in college General Chemistry. Alcohol, Chemistry and You, by Dr. Bill Boggan, is the latest offering by the Web site, which "looks at the chemistry of beverage alcohol (ethyl alcohol) through the eyes of a General Chemistry student." The fourteen chapter lessons cover everything from what ethyl alcohol is to alcohol addiction, relating it to various principles learned in a general chemistry course.

2001-01-01

354

Geothermal hot water system  

SciTech Connect

Geothermal hot water system including a hot water tank and a warm water tank which are heated independently of each other by a close loop freon system. The closed loop freon system includes a main condenser which heats water for the warm water tank and a super-heated condenser which heats water for the hot water tank, and where the freon passes through a water evaporator which is heated by water such as from a well or other suitable source. The water evaporator in the closed loop freon system passes the water through but no environmental change to the water. An electrical circuit including aquastats in the warm water tank connected therethrough controls operation of the closed loop freon system including respective pumps on the super-heated condenser and main condenser for pumping water. Pumps pump water through the main condenser for the warm tank and through the super-heated condenser for the hot tank. The system provides for energy conservation in that the head pressure of the compressor is kept in the lower operating ranges as determined by the discharge flow of the main condenser which varies by the head pressure and temperature flow control which varies by temperature. The geothermal hot water system uses a least amount of energy in heating the water in the hot tank as well as the warm tank.

Dittell, E.W.

1983-05-10

355

Cannabinoids: occurrence and medicinal chemistry.  

PubMed

With an inventory of several hundreds secondary metabolites identified, Cannabis sativa L. (hemp) is one of the phytochemically best characterized plant species. The biomedical relevance of hemp undoubtedly underlies the wealth of data on its constituents and their biological activities, and cannabinoids, a class of unique meroterpenoids derived from the alkylation of an olivetollike alkyl resorcinol with a monoterpene unit, are the most typical constituents of Cannabis. In addition to the well-known psychotropic properties of ?(9)-THC, cannabinoids have been reported to show potential in various fields of medicine, with the capacity to address unmet needs like the relief of chemotherapy-derived nausea and anorexia, and symptomatic mitigation of multiple sclerosis. Many of the potential therapeutic uses of cannabinoids are related to the interaction with (at least) two cannabinoid G-protein coupled receptors (CB1 and CB2). However, a number of activities, like the antibacterial or the antitumor properties are non totally dependent or fully independent from the interaction with these proteins. These pharmacological activities are particularly interesting since, in principle, they could be easily dissociated by the unwanted psychotropic effects. This review aims at giving readers a survey of the more recent advances in both phytochemistry of C. sativa, the medicinal chemistry of cannabinoids, and their distribution in plants, highlighting the impact that research in these hot fields could have for modern medicinal chemistry and pharmacology. PMID:21254969

Appendino, G; Chianese, G; Taglialatela-Scafati, O

2011-01-01

356

Automatic hot water recovery system  

Microsoft Academic Search

A heat recovery system recovers hot water to an insulated tank through reciprocally variable volume chambers which are biased to draw water from hot water lines when the pressure throughout the system is equalized. One-way valving means permits continuous water flow when desired through the hot water tank to the hot water outlet. In a specific embodiment, bias is effected

Haws

1985-01-01

357

Hot Carbon Corona in Mars’ Upper Thermosphere and Exosphere  

NASA Astrophysics Data System (ADS)

The production of energetic particles results in the formation of the hot corona, where the most of the escape of neutral atoms occur, in the Martian upper atmosphere. In order to investigate the dynamics of these energetic neutral atoms, we have carried out a study that provides a self-consistent global description of the hot corona in the upper thermosphere and exosphere by employing a self-consistent global kinetic model coupled with a thermosphere/ionosphere model. In this work, we evaluate the carbon atom inventory by studying the production and distribution of energetic carbon atoms. The most important source reactions for hot atomic carbon are expected to be photodissociation of CO and dissociative recombination of CO+, which are highly sensitive to solar activity and occur mostly deep in the dayside of the thermosphere. The latest available branching ratios is adopted, and appropriate choices of the rate coefficient and the photodissociation frequencies are made. In this study, we simulate the variations of the hot carbon corona over the solar cycle and seasons. The spatial distributions and profiles of density and temperature, atmospheric loss rates are discussed for the cases considered. The total global escape of hot carbon from all dominant photochemical processes is computed and compared with those from other previous models. To describe self-consistently the upper thermosphere and exosphere, a combination of our 3D Direct Simulation Monte Carlo (DSMC) model [Valeille, A., Combi, M., Bougher, S., Tenishev, V., Nagy, A., 2009. J. Geophys. Res. 114, E11006. doi:10.1029/2009JE003389] and the 3D Mars Thermosphere General Circulation Model (MTGCM) [Bougher, S. W., Bell, J. M., Murphy, J. R., Lopez-Valverde, M. A., Withers, P. G., 2006. Geophys. Res. Lett. 32, doi: 10.1029/2005GL024059. L02203] is used. Finally, our computed global total escape rate of hot carbon ranges ~ (5.2 - 57.1) × 1023 s-1 for the aphelion solar low to perihelion solar high case.

Lee, Yuni; Combi, M.; Tenishev, V.; Bougher, S.

2013-10-01

358

The hot list strategy.  

SciTech Connect

Experimentation strongly suggests that, for attacking deep questions and hard problems with the assistance of an automated reasoning program, the more effective paradigms rely on the retention of deduced information. A significant obstacle ordinarily presented by such a paradigm is the deduction and retention of one or more needed conclusions whose complexity sharply delays their consideration. To mitigate the severity of the cited obstacle, I formulated and feature in this article the hot list strategy. The hot list strategy asks the researcher to choose, usually from among the input statements characterizing the problem under study, one or more statements that are conjectured to play a key role for assignment completion. The chosen statements--conjectured to merit revisiting, again and again--are placed in an input list of statements, called the hot list. When an automated reasoning program has decided to retain a new conclusion C--before any other statement is chosen to initiate conclusion drawing--the presence of a nonempty hot list (with an appropriate assignment of the input parameter known as heat) causes each inference rule in use to be applied to C together with the appropriate number of members of the hot list. Members of the hot list are used to complete applications of inference rules and not to initiate applications. The use of the hot list strategy thus enables an automated reasoning program to briefly consider a newly retained conclusion whose complexity would otherwise prevent its use for perhaps many CPU-hours. To give evidence of the value of the strategy, I focus on four contexts: (1) dramatically reducing the CPU time required to reach a desired goal, (2) finding a proof of a theorem that had previously resisted all but the more inventive automated attempts, (3) discovering a proof that is more elegant than previously known, and (4) answering a question that had steadfastly eluded researchers relying on an automated reasoning program. I also discuss a related strategy, the dynamic hot list strategy (formulated by my colleague W. McCune), that enables the program during a run to augment the contents of the hot list. In the Appendix, I give useful input files and interesting proofs. Because of frequent requests to do so, I include challenge problems to consider, commentary on my approach to experimentation and research, and suggestions to guide one in the use of McCunes automated reasoning program OTTER.

Wos, L.; Pieper, G. W.; Mathematics and Computer Science

1999-01-01

359

Hot-Water Worms May Use Bacteria as Shield  

NSDL National Science Digital Library

This National Geographic news article highlights research being done to study the Pompeii worm (Alvinella pompejana), the most heat tolerant complex organism on Earth, and its microscopic symbionts. Bacteria on the worms' backs act like firefighters' blankets, shielding the worms from intermittent blasts of hot, metal-rich water. Scientists are currently characterizing the chemistry of the vent environment by sequencing a large amount of DNA from the bacterial community-the metagenome. The page includes links to related National Geographic sites.

Roach, John

2009-06-17

360

Atomic Weights No Longer Constants of Nature  

SciTech Connect

Many of us grew up being taught that the standard atomic weights we found in the back of our chemistry textbooks or on the Periodic Table of the Chemical Elements hanging on the wall of our chemistry classroom are constants of nature. This was common knowledge for more than a century and a half, but not anymore. The following text explains how advances in chemical instrumentation and isotopic analysis has changed the way we view atomic weights and why they are no longer constants of nature.

Coplen, T.B.; Holden, N.

2011-03-01

361

DISEQUILIBRIUM CARBON, OXYGEN, AND NITROGEN CHEMISTRY IN THE ATMOSPHERES OF HD 189733b AND HD 209458b  

SciTech Connect

We have developed a one-dimensional photochemical and thermochemical kinetics and diffusion model to study the effects of disequilibrium chemistry on the atmospheric composition of 'hot-Jupiter' exoplanets. Here we investigate the coupled chemistry of neutral carbon, hydrogen, oxygen, and nitrogen species on HD 189733b and HD 209458b and we compare the model results with existing transit and eclipse observations. We find that the vertical profiles of molecular constituents are significantly affected by transport-induced quenching and photochemistry, particularly on the cooler HD 189733b; however, the warmer stratospheric temperatures on HD 209458b help maintain thermochemical equilibrium and reduce the effects of disequilibrium chemistry. For both planets, the methane and ammonia mole fractions are found to be enhanced over their equilibrium values at pressures of a few bar to less than an mbar due to transport-induced quenching, but CH{sub 4} and NH{sub 3} are photochemically removed at higher altitudes. Disequilibrium chemistry also enhances atomic species, unsaturated hydrocarbons (particularly C{sub 2}H{sub 2}), some nitriles (particularly HCN), and radicals like OH, CH{sub 3}, and NH{sub 2}. In contrast, CO, H{sub 2}O, N{sub 2}, and CO{sub 2} more closely follow their equilibrium profiles, except at pressures {approx}<1 {mu}bar, where CO, H{sub 2}O, and N{sub 2} are photochemically destroyed and CO{sub 2} is produced before its eventual high-altitude destruction. The enhanced abundances of CH{sub 4}, NH{sub 3}, and HCN are expected to affect the spectral signatures and thermal profiles of HD 189733b and other relatively cool, transiting exoplanets. We examine the sensitivity of our results to the assumed temperature structure and eddy diffusion coefficients and discuss further observational consequences of these models.

Moses, Julianne I. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); Visscher, C. [Lunar and Planetary Institute, Houston, TX 77058 (United States); Fortney, J. J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Showman, A. P.; Lewis, N. K.; Griffith, C. A. [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Klippenstein, S. J. [Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Shabram, M. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Friedson, A. J. [Earth and Space Sciences Division, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Marley, M. S.; Freedman, R. S., E-mail: jmoses@spacescience.org [NASA Ames Research Center, Moffett Field, CA 94035 (United States)

2011-08-10

362

Beppu hot springs  

SciTech Connect

Beppu is one of the largest hot springs resorts in Japan. There are numerous fumaroles and hot springs scattered on a fan-shaped area, extending 5 km (3.1 miles) from east to west and 8 km (5.0 miles) from north to south. Some of the thermal manifestations are called {open_quotes}Jigoku (Hells){close_quotes}, and are of interest to visitors. The total amount of discharged hot springs water is estimated to be 50,000 ton/day (9,200 gpm) indicating a huge geothermal system. The biggest hotel in Beppu (Suginoi Hotel) installed a 3-MW geothermal power plant in 1981 to generate electricity for its own private use.

Taguchi, Schihiro [Fukuoka Univ. (Japan); Itoi, Ryuichi [Kyushu Univ., Kasuga (Japan); Yusa, Yuki [Kyoto Univ., Beppu (Japan)

1996-05-01

363

CHEMISTRY: Harnessing the Power of Diatomics  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required. When a diatomic molecule is broken up into its constituent atoms, these very energetic atoms provide a large driving force for further reaction. Diatomic molecules often do not undergo productive chemistry, however, because the energy needed to break the diatomic bond is also high. In his Perspective, Thorp discusses the work by MacBeth et al., who have synthesized a nonheme iron complex that reacts with O2 to produce two equivalents of a metal-oxo complex. The complex elegantly mimic the ability of some enzymes to influence metal ion coordination spheres.

H. Holden Thorp (University of North Carolina at Chapel Hill;Department of Chemistry)

2000-08-11

364

General Chemistry Online!  

NSDL National Science Digital Library

General Chemistry Online, created by Frederick Senese, a professor at Frostburg State University, is a guide and resource for introductory chemistry students. This site provides five areas of information: The Chemistry Home Companion, Just Ask Antoine!, Chemistry Exam Survival Guide, Tutorials, and a Featured Article. The Companion is a study guide covering the basic concepts of an introductory general chemistry course. Topics include measurement, molecules and compounds, and the quantum theory. Just Ask Antoine! allows students to post their chemistry questions. An archived list provides questions and answers for the past year. The Exam Survival Guide provides tips on passing exams, checklists of objectives and skills, and two online practice exams. The Tutorial currently contains only problems and quizzes for the measurement topic. The featured article for February is about Anandamide, a "messenger molecule that plays a role in pain, depression, appetite, memory, and fertility."

Senese, Frederick A.

365

Atoms, Molecules, and Kinetic Theory, Science (Experimental): 5317.63.  

ERIC Educational Resources Information Center

|This course of instruction in advanced chemistry is intended for the student ready for first-year college chemistry. Presented is an in-depth review with theory and mathematics being stressed in the study of concepts involving atomic structure, bonding, states of matter, molar relationships in equations, and properties of solutions. It is…

Buffaloe, Jacquelin F.

366

Autoxidation of Hydrocarbons: From Chemistry to Catalysis  

Microsoft Academic Search

This contribution summarizes our recent efforts to unravel the radical chemistry of autoxidations. Abstraction of the weakly\\u000a bonded ?H-atom of the primary hydroperoxide product by chain carrying peroxyl radicals is identified as the source of major\\u000a end products such as alcohol and ketone\\/aldehyde. In the case of cyclohexane autoxidation, this reaction is even responsible\\u000a for the majority of ring-opened by-products.

Ive Hermans; Jozef Peeters; Pierre A. Jacobs

2008-01-01

367

Middle School Chemistry  

NSDL National Science Digital Library

Middle school science resource from ACS. It includes activity-based lesson plans for teaching basic chemistry concepts that cover all the main concepts in middle school chemistry. Each lesson also contains integrated animations and video that a teacher can use to help explain student observations on the molecular level. Online professional development will also be available to introduce and familiarize teachers with the demonstrations, activities, and chemistry content in the site.

368

Kurnakov and analytical chemistry  

Microsoft Academic Search

The paper appreciates the role of Academician N.S. Kurnakov in holding the All-Union Conference on Analytical Chemistry (1939)\\u000a and creating the Commission on Analytical Chemistry at the Academy of Sciences of the USSR. The scientific works of Kurnakov\\u000a relating to chemical analysis are indicated; brief review is given to studies on analytical chemistry that were carried out\\u000a in the collectives

Yu. A. Zolotov

2010-01-01

369

Hot piston ring tests  

SciTech Connect

As part of the DOE/NASA Automotive Stirling Engine Project, tests were made at NASA Lewis Research Center to determine whether appendix gap losses could be reduced and Stirling engine performance increased by installing an additional piston ring near the top of each piston dome. An MTI-designed upgraded Mod I Automotive Stirling Engine was used for these tests. Unlike the conventional rings at the bottom of the piston, these rings operated in a high temperature environment (700/sup 0/C). Because of this, we called them ''hot-rings.'' It was necessary that they be made of a high temperature alloy (Stellite 6B) and that a high temperature solid lubricant coating (NASA Lewis-developed PS-200) be applied to the cylinder walls. Engine tests were run at 5, 10, and 15 MPa operating pressure over a range of operating speeds. Tests were run both with the hot-rings in place and without them to pro-side a baseline for comparison. Although budget and schedule restrictions severely limited the testing, the minimum data to assess the potential of both the hot-rings and high temperature low friction coating was obtained. Results indicated a slight increase in power and efficiency with the hot-rings over the baseline configuration. This increase was over and above the friction loss introduced by the hot-rings. Seal leakage measurements showed a significant reduction in leakage with the hot-rings in place. In addition, cylinder wall temperature measurements indicated less cylinder heating in the appendix gap area - between the lower piston rings and the hot-ring. Approximately 22.4 hours of ring-on-coating operation were recorded. After the initial break-in period, wear on both the rings and the coating was low. The PS-200 coating seems to offer significant potential for long-term operation at high temperatures. Both the hot-ring and the PS-200 low friction coating show promise and should be pursued further.

Allen, D.J.; Tomazic, W.A.

1987-01-01

370

Science Update: Analytical Chemistry.  

ERIC Educational Resources Information Center

|Briefly discusses new instrumentation in the field of analytical chemistry. Advances in liquid chromatography, photoacoustic spectroscopy, the use of lasers, and mass spectrometry are also discussed. (CS)|

Worthy, Ward

1980-01-01

371

Environmental chemistry: Volume B  

SciTech Connect

This is an extensive introduction to environmental chemistry for engineering and chemical professionals. The contents of Volume B include equilibria processes, chemical processes, biochemical processes, and physicochemical processes.

Yen, T.F.

1999-08-01

372

Atomic Mobile  

NSDL National Science Digital Library

Learners make a mobile model of a carbon atom using clay, wire, and pipe cleaners. Learners will use the periodic table as a guide and explore how atoms are made up of a nucleus of protons and neutrons with orbiting electrons. The activity includes a PDF file of a periodic table and a guide for reading it.

History, American M.

2012-06-26

373

Atom Builder  

NSDL National Science Digital Library

This is a virtual manipulative that students may use to construct various atoms up to carbon by creating protons and neutrons from up and down quarks and adding electrons. Students are challenged to keep the electrical charge of the atom neutral and to ensure the imbalance between protons and neutrons doesn't become great enough to result in radioactive decay!

Online, Nova

2011-02-08

374

Democritean Atomism  

Microsoft Academic Search

An atomic structure of matter was proposed by Leucippus and Democritus in Ancient Greece in the fifth century bc as a response to an argument of Parmenides to the effect that change is impossible. For the ancient atomists permanent reality\\u000a consists of portions of being (atoms) each characterised by an unchanging shape and size. Change involves the motion and rearrangement

Alan Chalmers

375

Open access and medicinal chemistry  

PubMed Central

Chemistry Central is a new open access website for chemists publishing peer-reviewed research in chemistry from a range of open access journals. A new addition, Chemistry Central Journal, will cover all of chemistry and will be broken down into discipline-specific sections, and Im delighted that Medicinal Chemistry will be a key discipline in this new journal.

Swain, Chris

2007-01-01

376

Atmospheric chemistry of HCF2O(CF2CF2O)xCF2H (x=2-4): kinetics and mechanisms of the chlorine-atom-initiated oxidation.  

PubMed

Smog chamber/FTIR techniques were used to measure k(Cl+HCF(2)O(CF(2)CF(2)O)(x)CF(2)H)=(5.3±1.5)×10(-17) cm(3) molecule(-1) s(-1) in 700 Torr of N(2)/O(2) diluent at 296±1 K. The Cl-initiated atmospheric oxidation of HCF(2)O(CF(2)CF(2)O)(x)CF(2)H, x=2,3 and 4, gave COF(2) in molar yields of (593±41)%, (758±71)% and (939±73)%, respectively, with no other observable carbon-containing products (i.e., essentially complete conversion of the hydrofluoropolyethers into COF(2)). Quantitative infrared spectra for HCF(2)O(CF(2)CF(2)O)(x)CF(2)H (x=2-4) were recorded and used to estimate the radiative efficiencies of the title compounds (1.07, 1.33, and 1.36 W m(-2) ppb(-1)). Global warming potentials (100 year time horizon) of 3870, 4730 and 5060 were estimated for HCF(2)O(CF(2)CF(2)O)(x)CF(2)H, x=2, 3 and 4, respectively. The results are discussed with respect to the atmospheric chemistry and environmental impact of hydrofluoropolyethers. PMID:20981750

Sulbaek Andersen, Mads P; Andersen, Vibeke F; Nielsen, Ole J; Sander, Stanley P; Wallington, Timothy J

2010-12-17

377

113. ARAI Hot cell (ARA626) Building wall sections and details ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

113. ARA-I Hot cell (ARA-626) Building wall sections and details of radio chemistry lab. Shows high-bay roof over hot cells and isolation rooms below grade storage pit for fuel elements. Norman Engineering Company: 961-area/SF-626-A-4. Date: January 1959. Ineel index code no. 068-0626-00-613-102724. - Idaho National Engineering Laboratory, Army Reactors Experimental Area, Scoville, Butte County, ID

378

Difficulties Implementing a Web Based PBL: Insight into Atomic Theory taught via a WebQuest  

Microsoft Academic Search

To foster student driven learning I developed a Web Quest that can teach atomic theory to a high school chemistry class. This Web Quest allows students the opportunity to examine the worlds of notable scientists that have contributed throughout time to the foundation of chemistry with their theories of atomic structure. The students' job is to defend the work of

Muhsinah L. Holmes

379

Hot Talk, Cold Science  

Microsoft Academic Search

One of the hottest topics in climate science is understanding and evaluating the impacts of possible global warming caused by anthropogenic emissions of greenhouse gases. In Hot Talk, Cold Science, S. Fred Singer does not accept global warming. Singer says in his preface, ``The purpose of this book is to demonstrate that the evidence [for global warming] is neither settled,

Robert J. Oglesby

1998-01-01

380

Hot off the Press  

ERIC Educational Resources Information Center

|In the past, the newspaper was one of the world's most used sources of information. Recently, however, its use has declined due to the popularity of cable television and the Internet. Yet the idea of reading the morning paper with a hot cup of coffee holds many warm memories for children who watched their parents in this daily ritual. In this…

Brisco, Nicole D.

2007-01-01

381

Hot corrosion of materials  

Microsoft Academic Search

Alloys and ceramics may experience accelerated corrosion at high temperatures when their surfaces are coated by a thin film of fused salt in an oxidizing environment. Because of their high thermodynamic stabilities, fused alkali sulfates are frequently deposited or condensed onto hot substrates from the combustion product gases or else by the oxidation of heavy metal contaminants in the fuel,

Robert A. Rapp

1990-01-01

382

China's 'Hot Money' Problems.  

National Technical Information Service (NTIS)

Economic conditions in China are of considerable concern to U.S. policy makers, given the potential impact of China's economy on the global and U.S. economy. The recent large inflow of financial capital into China, commonly referred to as 'hot money,' has...

M. F. Martin W. M. Morrison

2008-01-01

383

Hot Dry Rock - Summary  

Microsoft Academic Search

Hot Dry Rock adds a new flexibility to the utilization of geothermal energy. Almost always the approach has been to limit that utilization to places where there is a natural source of water associated with a source of heat. Actually, the result was that steam was mined. Clearly there are much larger heat resources available which lack natural water to

Tennyson; George P. Jr

1992-01-01

384

Hot piston ring tests  

NASA Astrophysics Data System (ADS)

As part of the DOE/NASA Automotive Stirling Engine Project, tests were made at NASA Lewis Research Center to determine whether appendix gap losses could be reduced and Stirling engine performance increased by installing an additional piston ring near the top of each piston dome. An MTI-designed upgraded Mod I Automotive Stirling Engine was used. Unlike the conventional rings at the bottom of the piston, these hot rings operated in a high temperature environment (700 C). They were made of a high temperature alloy (Stellite 6B) and a high temperature solid lubricant coating (NASA Lewis-developed PS-200) was applied to the cylinder walls. Engine tests were run at 5, 10, and 15 MPa operating pressure over a range of operating speeds. Tests were run both with hot rings and without to provide a baseline for comparison. Minimum data to assess the potential of both the hot rings and high temperature low friction coating was obtained. Results indicated a slight increase in power and efficiency, an increase over and above the friction loss introduced by the hot rings. Seal leakage measurements showed a significant reduction. Wear on both rings and coating was low.

Allen, David J.; Tomazic, William A.

1987-12-01

385

Hot oiling spreadsheet.  

National Technical Information Service (NTIS)

One of the most common oil-field treatments is hot oiling to remove paraffin from wells. Even though the practice is common, the thermal effectiveness of the process is not commonly understood. In order for producers to easily understand the thermodynamic...

A. J. Mansure

1996-01-01

386

What's Hot? What's Not?  

ERIC Educational Resources Information Center

When Goldilocks finds three bowls of porridge at different temperatures in the three bears' house, she accurately assesses the situation and comes up with one of the most recognizable lines in children's literature," This porridge is too hot; this porridge is too cold; aahh, this porridge is just right!" Goldilocks' famous line is a perfect…

Buczynski, Sandy

2006-01-01

387

Hot hands and equilibrium  

Microsoft Academic Search

Past literature suggests that success rates in professional basketball are independent of past performance and this has been interpreted as evidence that the commonly shared belief in Hot Hands (HH) is a cognitive illusion. This is often cited as evidence of biased decision making, even when financial stakes are high. We argue that this interpretation ignores changes in both teams’

Gil Aharoni; Oded H. Sarig

2011-01-01

388

Hot hands and equilibrium  

Microsoft Academic Search

Past literature suggests that success rates in professional basketball are independent of past performance and this has been interpreted as evidence that the commonly shared belief in Hot Hands (HH) is a cognitive illusion. This is often cited as evidence of biased decision making, even when financial stakes are high. We argue that this interpretation ignores changes in both teams’

Gil Aharoni; Oded H. Sarig

2012-01-01

389

Varmgasrensning. (Hot gas cleaning).  

National Technical Information Service (NTIS)

In relation to thermal power plants, the status of hot gas cleaning and the properties of tin oxide and the compounds formed in an impure coal gas are discussed and results of experiments with SnO(sub 2) masses are presented and evaluated. Possible cleani...

D. V. Nielsen P. E. Hoejlund Nielsen I. D. Sigurdardottir H. Christiansen

1993-01-01

390

Kamchatka's thermal hot springs  

NSDL National Science Digital Library

The Kamchatka Peninsula is featured in this website including information on geography, climate, fauna, flora, volcanoes, thermal springs, Valley of Geysers, native people, and options for travel in Kamchatka. This specific page highlights a selection of Kamchatka's hot springs, presenting basic information on temperature ranges, chemical and physical characteristics, surrounding vegetation, and general location.

Kamchatka, Vision O.

391

OECD Focus Hot File  

NSDL National Science Digital Library

In each issue of the Organization for Economic Co-operation and Development (OECD)'s Focus Hot File, recent books and government reports of interest are listed with summaries and contact information. Past listings may be browsed by country in the Focus Compendium, and related publications are hyperlinked throughout.

392

Some Like it Hot  

NSDL National Science Digital Library

NASA Astrobiologist Jack Farmer is featured in this web article that focuses on microrganisms found in Yellowstone hot springs and ocean floor hydrothermal vents. Included within the article are numerous links to concepts, resources, and further readings involving exobiology. and microbiology. Downloadable Quick time videos of a discussion with Farmer and hydrothermal vent activity at the ocean floor are also available.

Bortman, Henry; Magazine, Astrobiology

393

Refurbishment of an Analytical Laboratory Hot Cell Facility  

SciTech Connect

An Analytical Laboratory Hot Cell (ALHC) Facility at Argonne National Laboratory-West (ANL-W) was in service for nearly thirty years. In order to comply with DOE regulations governing such facilities and meet ANL-W programmatic requirements, a major refurbishment effort was undertaken. To place the facility in compliance with current regulations, all penetrations within the facility were sealed, the ventilation system was redesigned, upgraded and replaced, the master-slave manipulators were replaced, the hot cell windows were removed, refurbished, and reinstalled, all hot cell utilities were replaced, a lead-shielded glovebox housing an Inductive Coupled Plasma - Atomic Emission Spectrometer (ICP-AES) System was interfaced with the hot cells, and a new CO{sub 2} fire suppression system and other ALHC support equipment were installed.

Rosenberg, K.E.; Henslee, S.P.; Michelbacher, J.A.; Coleman, R.M.

1996-08-01

394

Practical hot oiling and hot watering for paraffin control.  

National Technical Information Service (NTIS)

One of the common oil-field wellbore problems is paraffin deposition. Even though hot oiling or hot watering is usually the first method tried for removing paraffin, few operators appreciate the limitations of ''hot oiling'' and the potential for the flui...

A. J. Mansure K. M. Barker

1994-01-01

395

Hot Tub Rash (Pseudomonas Folliculitis)  

MedlinePLUS

newsletter | contact Share | Hot Tub Rash ( Pseudomonas Folliculitis) Information for adults A A A This image displays follicular elevations of the skin and small pus-filled lesions. Overview Hot tub rash ( Pseudomonas folliculitis) is an infection of ...

396

Basic Chemistry Review  

NSDL National Science Digital Library

This assignment reviews basic of chemistry for students who should have had 2 introductory semesters of basic chemistry prior to enrolling in the Fundamental of Water Quality course for which the assignment is used. Assignment reviews basic equation balancing and questions about valence and concentration conversion that students will confront regularly in any geochemistry course.

Meixner, Thomas

397

Tropospheric Halogen Chemistry  

Microsoft Academic Search

Halogens are very reactive chemicals that are known to play an important role in anthropogenic stratospheric ozone depletion chemistry, first recognized by Molina and Rowland (1974). However, they also affect the chemistry of the troposphere. They are of special interest because they are involved in many reaction cycles that can affect the oxidation power of the atmosphere indirectly by influencing

R. von Glasow; P. J. Crutzen

2003-01-01

398

WATER CHEMISTRY ASSESSMENT METHODS  

EPA Science Inventory

This section summarizes and evaluates the surfce water column chemistry assessment methods for USEPA/EMAP-SW, USGS-NAQA, USEPA-RBP, Oho EPA, and MDNR-MBSS. The basic objective of surface water column chemistry assessment is to characterize surface water quality by measuring a sui...

399

Chemistry in Microfluidic Channels  

ERIC Educational Resources Information Center

|General chemistry introduces principles such as acid-base chemistry, mixing, and precipitation that are usually demonstrated in bulk solutions. In this laboratory experiment, we describe how chemical reactions can be performed in a microfluidic channel to show advanced concepts such as laminar fluid flow and controlled precipitation. Three sets…

Chia, Matthew C.; Sweeney, Christina M.; Odom, Teri W.

2011-01-01

400

Brushing Up on Chemistry.  

ERIC Educational Resources Information Center

Presents an activity designed for use during National Chemistry Week 2002 with the theme "Chemistry Keeps Us Clean". Allows students to discover more about a cleaning product they use everyday. Students make their own toothpaste and compare its properties with those of commercial toothpaste. (MM)

Trantow, Ashley

2002-01-01

401

Infrared Lasers in Chemistry.  

ERIC Educational Resources Information Center

|Selected infrared laser chemistry topics are discussed including carbon dioxide lasers, infrared quanta and molecules, laser-induced chemistry, structural isomerization (laser purification, sensitized reactions, and dielectric breakdown), and fundamental principles of laser isotope separation, focusing on uranium isotope separation. (JN)|

John, Phillip

1982-01-01

402

Laser applications in chemistry  

SciTech Connect

This book contains the proceedings from SPIE - The International Society for Optical Engineering conference on June 5-6, 1986. Topics are presented under the following session heads: Isotope Separation and Related Photochemistry, Laser Induced Chemistry I, Laser Spectroscopy, and Laser Induced Chemistry II. There are 33 papers in this volume.

Evans, D.K.

1986-01-01

403

Rolf Claessen's Chemistry Index  

NSDL National Science Digital Library

This award is given to sites, that somehow are related to chemistry. The criteria to rank the sites are information content and design (layout, navigation, graphical design). Sites must contain chemistry related topics as innovative and attractive as possible. This award is given away to the best 5% of the submissions to the website and other sites reviewed by site author.

404

Brushing Up on Chemistry.  

ERIC Educational Resources Information Center

|Presents an activity designed for use during National Chemistry Week 2002 with the theme "Chemistry Keeps Us Clean". Allows students to discover more about a cleaning product they use everyday. Students make their own toothpaste and compare its properties with those of commercial toothpaste. (MM)|

Trantow, Ashley

2002-01-01

405

Chemistry and Biology  

ERIC Educational Resources Information Center

|Discusses the relationship between chemisty and biology in the science curriculum. Points out the differences in perception of the disciplines, which the physical scientists favoring reductionism. Suggests that biology departments offer a special course for chemistry students, just as the chemistry departments have done for biology students.…

Wigston, David L.

1970-01-01

406

Chlorine Chemistry Division  

NSDL National Science Digital Library

This site is provided by the American Chemistry Council's Chlorine Chemistry Division. The page contains several links that give an introduction to chlorine, its uses, and issues surrounding the chemical compound. There is also a link to the Chlorine Science Center which provides classroom activities and a chlorine compound of the month.

2008-01-02

407

High Energy Halogen Chemistry.  

National Technical Information Service (NTIS)

Contents: Nitrosilicone Chemistry; Chemistry of 2-Fluoro-2-nitropropanediol; Experimental -- Bis(2-fluoro-2,2-dinitropropyl)silanediols; Reaction of bis(2-fluoro-2, 2-dinitropropyl) silanediol with chlorotrimethylsilane, Bis(3-3-fluoro-3,3-dinitropropyl)p...

K. Baum P. T. Berkowitz D. A. Lerdal

1978-01-01

408

Chemistry PowerPoint Lessons and Instructional Materials  

NSDL National Science Digital Library

Before becoming an author, Jeremy Schneider was a chemistry teacher. Over the past several years he has placed a number of helpful instructional resources here on his site. These particular resources cover atomic structure, quantum mechanics, atomic size, bonding, and several dozen additional topics. Visitors can browse through these resources at their leisure and each topic area includes a brief description of what is covered in each set of materials. Specifically, the resources include labs, assignments, worksheets, and handouts. Many of the resources draw on examples from the "Fundamentals of Chemistry" textbook, but the site suggests that page references from other textbooks can be substituted.

409

Measurements of atomic hydrogen temperature and methyl radical concentration in a diamond chemical vapor deposition reactor  

NASA Astrophysics Data System (ADS)

This investigation covers the development of nonintrusive, laser-based optical diagnostic tools for the measurement of trace amount molecular species in hostile, reactive environments such as plasmas. Two- photon laser induced fluorescence (LIF) spectroscopy is applied to obtain the temperature of atomic hydrogen and Cavity Ring-Down Spectroscopy (CRDS) to measure absolute concentrations of methyl radical in a hot filament diamond chemical vapor deposition (CVD) reactor. Atomic hydrogen (H) and methyl radical (CH3) are two abundant, reactive species in the hot filament diamond CVD process. An equilibrium temperature was deduced from the hydrogen Doppler line width at 20 Torr, which is the diamond deposition pressure in the reactor. The gas phase temperature measurement reached a high precision of 50 K due to a solar blind photo-multiplier tube was used that has the highest detection sensitivity at 121.6 nm of Lyman-? fluorescence and rejects efficiently the incandescent background. Resonant trapping of Lyman- ? raised difficulties in carrying out data analysis. For the condition of unsaturated two-photon absorption this study concluded that the Doppler line width is not related to the extent of re-absorption and re-emission of Lyman-? fluorescence. The dynamic range of the temperature measurement covers 400 K or higher providing no significant thermal ionization occurs. Methyl radical absorption is measured at the wavelength of 213.9 nm by CRDS, a sensitive linear absorption technique. An Abel transformation is required to convert the absorbance to the absolute concentration of methyl radicals based on the knowledge of the absorption cross-section at this wavelength. The spatial profile of the methyl concentration is at the order of 1014 molecules/cm3. A peak occurs 5 mm away from the filament, which indicates that methyl radical generation must involve gas-phase reaction, such as higher dissociation rate of methyl radical near filament, or density variation caused by temperature gradient rather than a direct dissociation process on the hot filament surface. Both measurements were carried out in the vicinity of the hot filament or between the filament and the substrate for diamond deposition with a spatial resolution of 0.2 mm. The results also demonstrated that the presence of a substrate influences on both the temperature and concentration measurements. This work increases our understanding of the hot filament diamond CVD process and demonstrated two reliable, advanced laser-based diagnostic methods that are of general importance for extracting parameters of basic interest in plasma chemistry such as temperature and absolute concentrations of gas-phase species at trace amounts nearby.

Ma, Yeming

410

Acting Atoms.  

ERIC Educational Resources Information Center

|Describes a fun game in which students act as electrons, protons, and neutrons. This activity is designed to help students develop a concrete understanding of the abstract concept of atomic structure. (DKM)|

Farin, Susan Archie

1997-01-01

411

Atom Lasers.  

National Technical Information Service (NTIS)

The general goal of this research was the generation, manipulation and characterization of coherent and non-classical matter waves, including atom lasers. The research involved both a theoretical and an experimental component. Major achievements from the ...

P. Meystre P. Jessen

2000-01-01

412

Secondary atomization  

Microsoft Academic Search

When a drop is subjected to a surrounding dispersed phase that is moving at an initial relative velocity, aerodynamic forces\\u000a will cause it to deform and fragment. This is referred to as secondary atomization. In this paper, the abundant literature\\u000a on secondary atomization experimental methods, breakup morphology, breakup times, fragment size and velocity distributions,\\u000a and modeling efforts is reviewed and

D. R. Guildenbecher; C. López-Rivera; P. E. Sojka

2009-01-01

413

Korean Kimchi Chemistry: A Multicultural Chemistry Connection  

ERIC Educational Resources Information Center

|Connecting science with different cultures is one way to interest students in science, to relate science to their lives, and at the same time to broaden their horizons in a variety of ways. In the lesson described here, students make kimchi, a delicious and popular Korean dish that can be used to explore many important chemistry concepts,…

Murfin, Brian

2009-01-01

414

EVOLVING FROM GREEN CHEMISTRY TO SUSTAINABLE CHEMISTRY  

EPA Science Inventory

The twelve principles of green chemistry provide a foundation and pathway which allows researchers to incorporate greenness into existing reactions or when developing new technologies. Research from our laboratory has adopted many of these principles and utlizes them as a major c...

415

Korean Kimchi Chemistry: A Multicultural Chemistry Connection  

ERIC Educational Resources Information Center

Connecting science with different cultures is one way to interest students in science, to relate science to their lives, and at the same time to broaden their horizons in a variety of ways. In the lesson described here, students make kimchi, a delicious and popular Korean dish that can be used to explore many important chemistry concepts,…

Murfin, Brian

2009-01-01

416

Improved measurement of atomic recoil frequency using atom interferometry  

NASA Astrophysics Data System (ADS)

We have recently used a single state time domain atom interferometer to make a measurement of atomic recoil frequency in cold ^85 Rb atoms precise to 2.5 ppm. The interferometer involves excitation by off-resonant standing wave pulses applied at t=0 and t=T. The pulses diffract and recombine a superposition of momentum states corresponding to the same internal state. This results in a population grating ``echo'' in the vicinity of t=2T. The grating was detected using an off resonant readout pulse. This pulse results in a backscattered signal detected using a heterodyne technique. Our measurement of the recoil frequency is in excellent agreement with the value of the recoil frequency obtained from previous measurements of the transition wavelength, atomic mass, and Planck's constant. We present improved measurements using PMT detection, reducing the effect of magnetic field gradients, and increasing the spatial extent of our interferometry beams. We also investigate the role of collisions between hot and cold ^85 Rb atoms on the lifetime of our echo signal and discuss the precision that can be achieved using an atomic fountain.

Beattie, Scott

2005-05-01

417

Microstructure Evolution of Gas Atomized Iron Based ODS Alloys  

SciTech Connect

In a simplified process to produce precursor powders for oxide dispersion-strength- ened (ODS) alloys, gas-atomization reaction synthesis (GARS) was used to induce a surface oxide layer on molten droplets of three differing erritic stainless steel alloys during break-up and rapid solidification. The chemistry of the surface oxide was identified using auger electron spectroscopy (AES) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The precursor iron-base powders were consolidated at 850 C and 1,300 C using hot isostatic pressing (HIPing). Consolidation at the lower temperature resulted in a fully dense microstructure, while preventing substantial prior particle-boundary-oxide dissociation. Microstructural analysis of the alloys consolidated at the higher temperature confirmed a significant reduction in prior-particle-boundary-oxide volume fraction, in comparison with the lower-temperature-consolidated sample. This provided evidence that a high-temperature internal oxygen-exchange reaction occurred between the metastable prior particle-boundary-oxide phase (chromium oxide) and the yttrium contained within each prior particle. This internal oxygen-exchange reaction is shown to result in the formation of yttrium-enriched oxide dispersoids throughout the alloy microstructure. The evolving microstructure was characterized using transmission electron microscopy (TEM) and high-energy X-ray diffraction (HE-XRD).

Rieken, J.R.; Anderson, I.E.; Kramer, M.J.; Anderegg, J.W.; Shechtman, D.

2009-12-01

418

Coherent control of atoms and molecules  

Microsoft Academic Search

Whenever scientific tools are significantly advanced; new discoveries soon follow. My thesis work relies on advances in ultrafast laser technology that allow precise control over the shape of sub 20-fs laser pulses. This laser system enabled many new experiments that yielded significant advances in attosecond science, atomic physics; extreme nonlinear optics, quantum chemistry, coherent control, molecular physics, ultrafast optical phase

Randy Alan Bartels

2002-01-01

419

The hot chocolate effect  

NASA Astrophysics Data System (ADS)

The ''hot chocolate effect'' was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one-quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the 10% accuracy of the experiments.

Crawford, Frank S.

1982-05-01

420

Hot fire, cool soil  

NASA Astrophysics Data System (ADS)

Wildfires greatly increase a landscape's vulnerability to flooding and erosion events by removing vegetation and changing soils. Fire damage to soil increases with increasing soil temperature, and, for fires where smoldering combustion is absent, the current understanding is that soil temperatures increase as fuel load and fire intensity increase. Here, however, we show that this understanding that is based on experiments under homogeneous conditions does not necessarily apply at the more relevant larger scale where soils, vegetation, and fire characteristics are heterogeneous. In a catchment-scale fire experiment, soils were surprisingly cool where fuel load was high and fire was hot and, conversely, soils were hot where expected to be cooler. This indicates that the greatest fire damage to soil can occur where fuel load and fire intensity are low rather than high, and has important implications for management of fire-prone areas prior to, during, and after fire events.

Stoof, Cathelijne R.; Moore, Demie; Fernandes, Paulo M.; Stoorvogel, Jetse J.; Fernandes, Ricardo E. S.; Ferreira, António J. D.; Ritsema, Coen J.

2013-04-01

421

THE HOT CHOCOLATE EFFECT  

SciTech Connect

The "hot chocolate effect" was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the ten percent accuracy of the experiments.

Crawford, Frank S.

1980-12-01

422

Hot chocolate effect  

SciTech Connect

The ''hot chocolate effect'' was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one-quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the 10% accuracy of the experiments.

Crawford, F.S.

1982-05-01

423

Policing Crime Hot Spots  

Microsoft Academic Search

In recent years, crime scholars and practitioners have pointed to the potential benefits of focusing crime prevention efforts\\u000a on crime places. A number of studies suggest that crime is not spread evenly across city landscapes. Rather, there is significant\\u000a clustering of a crime in small places, or “hot spots,” that generate half of all criminal events (Pierce et al., 1988;

Anthony A. Braga

424

The ''hot'' patella  

SciTech Connect

Increased patellar uptake on bone scans is seen quite commonly but the possible or probable etiologies of this finding have not been previously well described. A review of 100 consecutive bone scans showed that the incidence of bilateral ''hot'' patellae is 15%. Identified etiologies include osteoarthritic degenerative disease (35%), fracture, possible metastatic disease, bursitis, Paget's disease, and osteomyelitis. The value of careful history, physical examination, and radiographs is stressed.

Kipper, M.S.; Alazraki, N.P.; Feiglin, D.H.

1982-01-01

425

Hot refueling hazards.  

PubMed

Hot refueling in the special operations community has several potential hazards which can accompany the operation. The MC-130 Panel Operator's (PO) position is located in the exhaust of the number 3 engine, subjecting him to fumes, heat, and exhaust blast. The hypothesis was that time constraints should be implemented to the work load due to heat and carbon monoxide exposure. The hypothesis was confirmed for heat exposure but not for significant carbon monoxide exposure. PMID:2496343

Hammer, D L

1989-03-01

426

Moderator Chemistry Program  

SciTech Connect

Over the past fifteen months, the Systems Chemistry Group of the Reactor Engineering Department has undertaken a comprehensive study of the Department's moderator chemistry program at Savannah River Site (SRS). An internal review was developed to formalize and document this program. Objectives were as outlined in a mission statement and action plan. In addition to the mission statement and action plan, nine separate task reports have been issued during the course of this study. Each of these task reports is included in this document as a chapter. This document is an organized compilation of the individual reports issued by the Systems Chemistry Group in assessment of SRS moderator chemistry to determine if there were significant gaps in the program as ft existed in October, 1989. While these reviews found no significant gaps in that mode of operation, or any items that adversely affected safety, items were identified that could be improved. Many of the items have already been dear with or are in the process of completion under this Moderator Chemistry Program and other Reactor Restart programs. A complete list of the items of improvement found under this assessment is found in Chapter 9, along with a proposed time table for correcting remaining items that can be improved for the chemistry program of SRS reactors. An additional external review of the moderator chemistry processes, recommendations, and responses to/from the Reactor Corrosion Mitigation Committee is included as Appendix to this compilation.

Dewitt, L.V.; Gibbs, A.; Lambert, D.P.; Bohrer, S.R.; Fanning, R.L.; Houston, M.W.; Stinson, S.L.; Deible, R.W.; Abdel-Khalik, S.I.

1990-11-01

427

Moderator Chemistry Program  

SciTech Connect

Over the past fifteen months, the Systems Chemistry Group of the Reactor Engineering Department has undertaken a comprehensive study of the Department`s moderator chemistry program at Savannah River Site (SRS). An internal review was developed to formalize and document this program. Objectives were as outlined in a mission statement and action plan. In addition to the mission statement and action plan, nine separate task reports have been issued during the course of this study. Each of these task reports is included in this document as a chapter. This document is an organized compilation of the individual reports issued by the Systems Chemistry Group in assessment of SRS moderator chemistry to determine if there were significant gaps in the program as ft existed in October, 1989. While these reviews found no significant gaps in that mode of operation, or any items that adversely affected safety, items were identified that could be improved. Many of the items have already been dear with or are in the process of completion under this Moderator Chemistry Program and other Reactor Restart programs. A complete list of the items of improvement found under this assessment is found in Chapter 9, along with a proposed time table for correcting remaining items that can be improved for the chemistry program of SRS reactors. An additional external review of the moderator chemistry processes, recommendations, and responses to/from the Reactor Corrosion Mitigation Committee is included as Appendix to this compilation.

Dewitt, L.V.; Gibbs, A.; Lambert, D.P.; Bohrer, S.R.; Fanning, R.L.; Houston, M.W.; Stinson, S.L.; Deible, R.W.; Abdel-Khalik, S.I.

1990-11-01

428

Quarkonium in Hot Medium  

SciTech Connect

I review recent progress in studying quarkonium properties in hot medium as well as possible consequences for quarkonium production in heavy ion collisions. There has been considerable interest in studying quarkonia in hot medium since the publication of the famous Matsui and Satz paper. It has been argued that color screening in a deconfined QCD medium will suppress the existence of quarkonium states, signaling the formation of a quark-gluon plasma (QGP) in heavy-ion collisions. Although this idea was proposed a long time ago, first principle QCD calculations, which go beyond qualitative arguments, have been performed only recently. Such calculations include lattice QCD determinations of quarkonium correlators; potential model calculations of the quarkonium spectral functions with potentials based on lattice QCD, as well as effective field theory approaches that justify potential models and reveal new medium effects. Spectral properties of heavy quark bound states are important ingredients in modeling of heavy quarkonium production in hot medium as will be discussed later.

Petreczky, P.

2010-08-02

429

Transition metal chemistry in crossed molecular beams  

NASA Astrophysics Data System (ADS)

Bimolecular state-selective chemistry has been performed using the technique of crossed molecular beams. Systems of current study involve transition metal atoms (M) interacting with small hydrocarbons, in particular: Mo + CH4, Zr + C2H4, and V + C2H4. Atomic metal reactants are prepared state-specifically by laser excitation followed by radiative decay. Nascent products were allowed to drift to a triply differentially pumped detector where they were ionized by either conventional electron impact or VUV photoionization and counted to obtain product angular and velocity distributions. C-H bond activation was observed for the former two systems, but not for the V systems. This behavior is rationalized in terms of the electronic configurations of the atomic reactants.

Willis, Peter A.; Stauffer, Hans U.; Hinrichs, Ryan Z.; Davis, H. Floyd

1998-05-01

430

How Single Atoms Move During a Quantum Corral Construction  

NASA Astrophysics Data System (ADS)

Precise positioning of single atoms/molecules using an STM-tip on crystal surfaces is a 'hot research topic' since it allows construction of man-designed artificial structures engineered on an atomic basis. Successful relocation of single atoms with atomic level precision requires an extremely fine control over the tip-atom-surface interactions. Here we describe how single atoms move during construction of quantum corral structures on a Ag(111) surface using the tip of a scanning tunneling microscope (STM). The manipulation signals of individual Ag atoms reveal the surface energetic configurations, the nature of the tip-atom interaction and remarkably detailed atom movement mechanisms with atomic level precisions. During the manipulation along the surface close-packed atomic row ([110] directions), the Ag atom moves in a pulling mode with single atomic site hops to follow the tip. However, when the tip-paths are deviated from the close-packed row directions, complex manipulation behaviours are observed. At smaller deviation angles from the [110] directions, the atom hops both hcp-fcc sites. When the manipulation paths are away from the [110] directions, the Ag atom moves with periodic 'move-rest-jump' circles. This detailed knowledge on the STM manipulation provides important information necessary for the development of 'automated atom manipulation' where real-time controlled computer programs will allow construction of desired artificial structures or assembling of prototype nano-devices on crystal surfaces on an atom-by-atom basis.

Braun, Kai-Felix; Hla, Saw-Wai; Rieder, Karl-Heinz

2003-03-01

431

The Chemistry Resource Center  

NSDL National Science Digital Library

Maintained by the British Columbia Institute of Technology Chemistry Department, The Chemistry Resource Center Web site bills itself as "on-line multi-media tutor to direct students to find textbook references, interesting WWW links and to guide them to solve Chemistry problems." Among the many activities on the site, probably the most interesting is the "How well do you know your Periodic Table?" link, which helps to teach students the basics of the elements and the periodic table through a unique interactive online exercise.

2000-01-01

432

Wizardry and Chemistry  

NSDL National Science Digital Library

Students learn how common pop culture references (Harry Potter books) can relate to chemistry. While making and demonstrating their own low-intensity sparklers (muggle-versions of magic wands), students learn and come to appreciate the chemistry involved (reaction rates, Gibb's free energy, process chemistry and metallurgy). The fun part is that all wands are personalized and depend on how well students conduct the lab. Students end the activity with a class duelâa face-off between wands of two different chemical compositions. This lab serves as a fun, engaging review for stoichiometry, thermodynamics, redox and kinetics, as well as advanced placement course review.

University Of Houston

433

Microscale Gas Chemistry  

NSDL National Science Digital Library

Created by Professor Bruce M. Mattson, PhD, of Creighton University's Department of Chemistry, the Microscale Gas Chemistry Website "provides instructions for the generation of gases on a microscale level along with instructions for chemical demonstrations and student laboratory experiments with the gases." The no-frills site, designed for high school and university chemistry teachers, contains clear and careful instructions for experiments with carbon dioxide, hydrogen, oxygen and nitrogen, nitrogen oxides, ammonia, ethene, chlorine, carbon monoxide, and more. An introduction offers two low-tech methods for gas generation. Data pages for relevant gases are linked to each experiment.

434

Materials Chemistry at SFU  

NSDL National Science Digital Library

The Materials Science group at Simon Fraser University (SFU) developed this website to address the group's primary research interests in material synthesis, molecular, electronics, and photonics. Visitors will find explanations covering sixteen research topics including chemical sensors, lithography, non-linear optics, and supramolecular chemistry. Under each topic heading, users will find links discussing the faculties' current goals, recent publications, and patents. The site also features links to the Pacific Centre for Advanced Materials and Microstructures; a collaborative effort between the Materials Science group at SFU and the physics and chemistry departments at the University of British Columbia. Anyone searching for the latest investigations in materials chemistry will find this website very informative.

435

Atomic force microscopy and x-ray photoelectron spectroscopy investigations of the morphology and chemistry of a PdCl{sub 2}/SnCl{sub 2} electroless plating catalysis system adsorbed onto shape memory alloy particles  

SciTech Connect

A study of the different stages of the electroless deposition of copper on micronic NiTi shape memory alloy particles activated by one-step and two-step methods has been conducted from both a chemical and a morphological point of view. The combination of x-ray photoelectron spectroscopy (XPS) measurements and atomic force microscopy (AFM) imaging has allowed detection of the distribution of the formed compounds and depth quantification and estimation of the surface topographic parameters. For the two-step method, at the sensitization of the early stages, it is observed by AFM that Sn is absorbed in form of clusters that tend to completely cover the surface and form a continuous film. XPS analysis have shown that Sn and Pd are first absorbed in form of oxide (SnO{sub 2} and PdO) and hydroxide [Sn(OH){sub 4}]. After the entire sensitization step, the NiTi substrate is covered with Sn-based compounds. After the sensitization and the activation steps the powder roughness increases. Behavior of the Sn and Pd growth for the one-step method does not follow the behavior found for the two-step method. Indeed, XPS analysis shows a three-dimensional (3D) growth of Pd clusters on top of a mixture of metallic tin, oxide (SnO) and hydroxide [Sn(OH){sub 2}]. These Pd clusters are covered with a thin layer of Pd-oxide contamination induced by the electroless process. The mean roughness for the one-step and two-step processes are equivalent. After copper deposition, the decrease of mean roughness is attributed to a filling of surface valleys, observed after the Sn-Pd coating step.

Silvain, J.F.; Fouassier, O.; Lescaux, S. [Institut de Chimie de la Matiere Condensee de Bordeaux (ICMCB) - CNRS, Universite de Bordeaux 1, 87 Avenue du Dr A. Schweitzer, F-33608 PESSAC (France); Veeco, Z.I. de la Gaudree, 11 Rue Marie Poussepin, F-91412 Dourdain (France)

2004-11-01

436

Near-monodisperse poly(2-(methacryloyloxy)ethyl phosphorylcholine)-based macromonomers prepared by atom transfer radical polymerization and thiol-ene click chemistry: novel reactive steric stabilizers for aqueous emulsion polymerization.  

PubMed

Poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) macromonomers have been prepared by the atom transfer radical polymerization (ATRP) of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) using a bifunctional disulfide-based initiator. To attach a terminal polymerizable methacrylate group, the central disulfide bond was cleaved and the resulting thiols were conjugated to 3-(acryloyloxy)-2-hydroxypropyl methacrylate using tris(2-carboxyethyl)phosphine (TCEP) in water. Here TCEP serves as both the disulfide cleavage agent and also the catalyst for the subsequent Michael addition, which is highly selective for the acrylate group. The resulting methacrylate-terminated macromonomers were used as a reactive steric stabilizer for the aqueous emulsion polymerization of styrene, yielding near-monodisperse PMPC-stabilized polystyrene (PS) latexes of around 100-200 nm in diameter. As a comparison, the disulfide-containing PMPC homopolymer precursor and the intermediate thiol-functional PMPC homopolymer (PMPC-SH) were also evaluated as potential steric stabilizers. Interestingly, near-monodisperse latexes were also obtained in each case. These three sterically-stabilized latexes, prepared using either PMPC macromonomer, disulfide-based PMPC homopolymer, or PMPC-SH homopolymer as a reactive steric stabilizer, remained colloidally stable after both freeze-thaw experiments and the addition of an electrolyte, indicating that a coronal layer of PMPC chains prevented flocculation in each case. In contrast, both a charge-stabilized PS latex prepared in the absence of any steric stabilizer and a PS latex prepared in the presence of a nonfunctional PMPC homopolymer exhibited very poor colloidal stability when subjected to a freeze-thaw cycle or the addition of an electrolyte, as expected. PMID:22191694

Warren, Nicholas J; Muise, Carl; Stephens, Alex; Armes, Steven P; Lewis, Andrew L

2012-01-23

437

Atom transfer radical polymerization from nanoparticles: a tool for the preparation of well-defined hybrid nanostructures and for understanding the chemistry of controlled/"living" radical polymerizations from surfaces.  

PubMed

Structurally well-defined polymer--nanoparticle hybrids were prepared by modifying the surface of silica nanoparticles with initiators for atom transfer radical polymerization and by using these initiator-modified nanoparticles as macroinitiators. Well-defined polymer chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined, densely grafted outer polystyrene or poly(methyl methacrylate) layer. In both cases, linear kinetic plots, linear plots of molecular weight (M(n)) versus conversion, increases in hydrodynamic diameter with increasing conversion, and narrow molecular weight distributions (M(w)/M(n)) for the grafted polymer samples were observed. Polymerizations of styrene from smaller (75-nm-diameter) silica nanoparticles exhibited good molecular weight control, while polymerizations of methyl methacrylate (MMA) from the same nanoparticles exhibited good molecular weight control only when a small amount of free initiator was added to the polymerization solution. The difference in polymerization behavior for styrene and MMA was ascribed to the facts that styrene undergoes thermal self-initiation while MMA does not and that termination processes involving freely diffusing chains are faster than those involving surface-bound chains. The polymerizations of both styrene and MMA from larger (300-nm-diameter) silica nanoparticles did not exhibit molecular weight control. This lack of control was ascribed to the very high initial monomer-to-initiator ratio in these polymerizations. Molecular weight control was induced by the addition of a small amount of free initiator to the polymerization but was not induced when 5--15 mol % of deactivator (Cu(II) complex) was added. PMID:11480969

von Werne, T; Patten, T E

2001-08-01

438

Sulfur Donor Atom Effects on Copper(I)/O2 Chemistry with Thioanisole Containing Tetradentate N3S Ligand Leading to ?-1,2-Peroxo-Dicopper(II) species  

PubMed Central

To better understand the effect of thioether coordination in copper-O2 chemistry, the tetradentate N3S ligand LASM (2-(methylthio)-N,N-bis((pyridin-2-yl)methyl)benzenamine) and related alkylether ligand LEOE (2-ethoxy-N,N-bis((pyridin-2-yl)methyl)ethanamine) have been studied. The corresponding copper(I) complexes, [(LASM)CuI]+ (1a) and [(LEOE)CuI]+ (3a) were studies as were the related compound [(LESE)CuI]+ (2a, LESE = (2-ethylthio-N,N-bis((pyridin-2-yl)methyl)ethanamine). The X-ray structure of 1a and its solution conductivity reveal a monomeric molecular structure possessing thioether coordination which persists in solution. In contrast, the C-O stretching frequencies of the derivative Cu(I)-CO complexes reveal that for these complexes, the modulated ligand arms, whether arylthioether, alkylthioether or ether, are not coordinated to the cuprous ion. Electrochemical data for 1a and 2a in CH3CN and DMF show the thioanisole moiety to be a poor electron donor compared to alkylthioether (1a is ~ 200 mV more positive than 2a). The structures of [(LASM)CuII(CH3OH)]2+ (1c) and [(LESE)CuII(CH3OH)]2+ (2c) have also been obtained and indicate nearly identical copper coordination environments. Oxygenation of 1a at reduced temperature gives a characteristic deep blue colored intermediate [{(LASM)CuII}2(O22?)]2+ (1bP) with absorption features at 442 (1,500 M?1cm?1), 530 (8,600 M?1cm?1) and 605 nm (10,400 M?1cm?1); these values compare well to the LMCT transitions previously reported for [{(LESE)CuII}2(O22?)]2+ (2bP). Resonance Raman data for [{(LASM)CuII}2(O22?)]2+ (1bP) support the formation of ?-1,2-peroxo species (?(O-O) = 828 cm?1 (?(18O2) = 48), ?sym(Cu-O) = 547 cm?1 (?(18O2) = 23) and ?asym(Cu-O) = 497 cm?1 (?(18O2) = 22) and suggest the LASM ligand is a poorer electron donor to copper than is LESE. In contrast, the oxygenation of [(LEOE)CuI]+ (3a), possessing an ether donor as an analogue of the thioether in LESE, led to the formation of a bis(?-oxo) species [{(LEOE)CuIII}2(O2?)2]2+ (3bO; 380 nm, ? ~ 10,000 M?1cm?1). This result provides further support for the sulfur influence in 1bP and 2bP, in particular coordination of the sulfur to the Cu. Thermal decomposition of 1bP is accompanied by ligand sulfoxidation. The structure of [{(LEOE)CuII(Cl)}2]+ (3c) generated from the reductive dehalogenation of organic chlorides suggests that the ether moiety is weakly bound to the cupric ion. A detailed discussion of the spectroscopic and structural characteristics of 1bP, 2bP and 3bO is presented.

Lee, Yunho; Lee, Dong-Heon; Park, Ga Young; Lucas, Heather R.; Sarjeant, Amy A. Narducci; Kieber-Emmons, Matthew T.; Vance, Michael A.; Milligan, Ashley E.; Solomon, Edward I.; Karlin, Kenneth D.

2010-01-01

439

Is It Time to Retire the Hybrid Atomic Orbital?  

ERIC Educational Resources Information Center

|A rationale for the removal of the hybrid atomic orbital from the chemistry curriculum is examined. Although the hybrid atomic orbital model does not accurately predict spectroscopic energies, many chemical educators continue to use and teach the model despite the confusion it can cause for students. Three arguments for retaining the model in the…

Grushow, Alexander

2011-01-01

440

Pittsburgh conference 1989 and exposition on analytical chemistry and applied spectroscopy (Abstracts)  

SciTech Connect

This book covers the proceedings of the 1989 Pittsburgh Conference and Exposition on Analytical Chemistry and Applied Spectroscopy. Some of the topics presented at the conference include the following: atomic spectroscopy; bioanalysis and life sciences; molecular spectroscopy; electroanalytical chemistry and gas chromotography.

Not Available

1989-01-01

441

Computer?assisted learning in the University of Surrey Chemistry Department  

Microsoft Academic Search

† Presented at the Conference on Computers in Higher Education held at Lancaster University, 29?31 March 1978.The use of computer?assisted learning to supplement conventional lecture and tutorial classes in a chemistry honours degree course is described. Graphics terminals have been employed extensively, and several topics in physical and inorganic chemistry have been covered. The packages developed for (1) atomic and

G. J. Buist

1978-01-01

442

Using Computer Visualization Models in High School Chemistry: The Role of Teacher Beliefs.  

ERIC Educational Resources Information Center

|This paper discusses the role of high school chemistry teachers' beliefs in implementing computer visualization software to teach atomic and molecular structure from a quantum mechanical perspective. The informants in this study were four high school chemistry teachers with comparable academic and professional backgrounds. These teachers received…

Robblee, Karen M.; Garik, Peter; Abegg, Gerald L.; Faux, Russell; Horwitz, Paul

443

The effects of computer animation on the particulate mental models of college chemistry students  

Microsoft Academic Search

Modern chemistry concepts have the particulate nature of matter at their core. Chemists explain most phenomena in terms of atomic and molecular models. The lack of understanding of chemistry concepts may be linked to the students' inability to build complete mental models that visualize particulate behavior. With computer animation technology, dynamic and three-dimensional presentations are possible. This study explores the

Vickie M. Williamson; Michael R. Abraham

1995-01-01

444

Curriculum Outline for Introduction to Engineering Chemistry. Second Edition. Review Cycle-Annual.  

ERIC Educational Resources Information Center

Introduction to Engineering Chemistry is a four-credit hour (one semester) course designed to introduce marine engineering students to the rudiments of basic (introductory) inorganic chemistry. The course consists of 18 units (numbered 1.0 through 18.0) focusing on these subject areas: fundamental concepts; structure of the atom and the periodic…

Schlenker, Richard M.

445

Curriculum Outline for Introduction to Engineering Chemistry. Second Edition. Review Cycle-Annual.  

ERIC Educational Resources Information Center

|Introduction to Engineering Chemistry is a four-credit hour (one semester) course designed to introduce marine engineering students to the rudiments of basic (introductory) inorganic chemistry. The course consists of 18 units (numbered 1.0 through 18.0) focusing on these subject areas: fundamental concepts; structure of the atom and the periodic…

Schlenker, Richard M.

446

PREFACE: Hot Quarks 2004  

NASA Astrophysics Data System (ADS)

Why another conference devoted to ultra-relativistic heavy-ion physics? As we looked around the landscape of the existing international conferences and workshops, we realized that there was not a single one tailored to the people who are most directly involved with the actual research work: students, post-docs, and junior faculty/research scientists. Of course there are schools, but that was not what we had in mind. We wanted a meeting where young researchers could come together to discuss in depth the physics that they are working on without any hindrance. The major conferences have very limited time for discussions which is often shared amongst the most established. This leaves little room for young people to ask their questions and to get the detailed feedback which they deserve and which satisfies their curiosity. A discussion-driven workshop, centering on those without whom there will be no future—that seemed like what was needed. And thus the Hot Quarks workshop was born. The aim of Hot Quarks was to enhance the direct exchange of scientific information among the younger members of the community, from both experiment and theory. Participation was by invitation only in order to emphasize the contributions from junior researchers. This approach makes the workshop unique among the many forums in the field. For young scientists it represented an opportunity for exposure that they would not have had in one of the major conferences. The hope is that this meeting has helped to stimulate the next generation of scientists in our field and, at the same time, strengthened their sense of community. It all came together from 18 24 July 2004, when the 77 participants met at The Inn at Snakedance in the Taos Ski Valley, New Mexico, USA, for the first Hot Quarks workshop. Photograph Participants gather in the sunshine at the foot of the Taos Ski Valley chairlift. By all accounts, Hot Quarks 2004 was a great success. Every participant had the opportunity to present her or his research and we spent an entire week talking physics and having fun from breakfast in the morning until late at night. A symbolic award was instituted for the best presentation at the workshop, dedicated to the memory of Klaus Kinder-Geiger, a sharp and brilliant young theorist who perished in the crash of Swissair Flight 111 on 2 September 1998 off the coast of Nova Scotia. It went to Denesh Molnar from Ohio State University for his outstanding talk on parton coalescence. The organizers wish to extend their gratitude to all participants for the high quality presentations making Hot Quarks 2004 a notable event. We are also very grateful for the superb hospitality of the staff of the Snakedance Inn, in particular Mitch Daniels who worked sheer miracles. Given the success of the first Hot Quarks workshop we decided to organize a second one, possibly even turning Hot Quarks into a series. The next meeting will be held in the late spring of 2006, probably in Italy. We hope it will be as memorable as the first one! Last but not least, we wish to thank all the generous sponsors of the conference: Brookhaven National Laboratory, European Organization for Nuclear Research (CERN), Gesellschaft fA~ 1/4 r Schwerionenforschung (GSI), Institute of Physics Publishing, Los Alamos National Laboratory, National Science Foundation, and Vanderbilt University. We are grateful for their support and are particularly happy that this support came from institutions both in the US and in Europe and from all the main experimental facilities that pursue a prominent heavy-ion program. Their support was essential for the success of a workshop targeting young scientists.

Antinori, Federico; Bass, Steffen A.; Bellwied, Rene; Ullrich, Thomas; Velkovska, Julia; Wiedemann, Urs

2005-04-01

447

Feshbach resonance cooling of trapped atom pairs  

SciTech Connect

Spectroscopic studies of few-body systems at ultracold temperatures provide valuable information that often cannot be extracted in a hot environment. Considering a pair of atoms, we propose a cooling mechanism that makes use of a scattering Feshbach resonance. Application of a series of time-dependent magnetic field ramps results in either zero, one, or two atoms remaining trapped. If two atoms remain in the trap after the field ramps are completed, then they have been cooled. Application of the proposed cooling mechanism to optical traps or lattices is considered.

Dunn, Josh W.; Borca, Bogdan; Greene, Chris H. [Department of Physics and JILA, University of Colorado, Boulder, Colorado 80309-0440 (United States); Blume, D. [Department of Physics, Washington State University, Pullman, Washington 99164-2814 (United States); Granger, B.E. [Department of Physics, Santa Clara University, Santa Clara, California 95053 (United States)

2005-03-01

448

HOT MOLECULAR CORES IN INFRARED DARK CLOUDS  

SciTech Connect

We present high angular resolution continuum images and molecular line spectra obtained at 345 GHz with the Submillimeter Array (SMA) toward two massive cores that lie within Infrared Dark Clouds (IRDCs): G034.43+00.24 MM1 and G024.33+00.11 MM1. Both of these cores contain bright, unresolved (<2'') objects that have previously been imaged in the millimeter/submillimeter continuum with the Institut de RadioAstronomie Millimetrique (IRAM) Plateau de Bure Interferometer and SMA and show complex molecular line chemistry. The new, higher angular resolution SMA continuum images reveal that both cores contain massive (8, 26 M{sub Sun }), unresolved (0.''6; {approx}3000 AU) continuum emission features and emission from many complex molecular transitions, which confirm that these are hot molecular cores, an early stage in the formation of a high-mass star. Because these hot cores are located within IRDCs, they may well represent the very earliest phases in the formation of high-mass protostars and, hence, their detailed study may reveal the initial conditions within high-mass star-forming cores, before they are shredded apart by stellar winds and radiation.

Rathborne, J. M.; Garay, G. [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Jackson, J. M. [Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States); Longmore, S.; Zhang, Q. [Harvard-Smithsonian Center for Astrophysics, Mail Stop 42, 60 Garden Street, Cambridge, MA 02138 (United States); Simon, R., E-mail: rathborn@das.uchile.cl, E-mail: guido@das.uchile.cl, E-mail: jackson@bu.edu, E-mail: slongmore@cfa.harvard.edu, E-mail: qzhang@cfa.harvard.edu, E-mail: simonr@ph1.uni-koeln.de [I.Physikalisches Institut, Universitaet zu Koeln, 50937 Koeln (Germany)

2011-11-10

449

Wanted: unique names for unique atom positions. PDB-wide analysis of diastereotopic atom names of small molecules containing diphosphate  

Microsoft Academic Search

BACKGROUND: Biological chemistry is very stereospecific. Nonetheless, the diastereotopic oxygen atoms of diphosphate-containing molecules in the Protein Data Bank (PDB) are often given names that do not uniquely distinguish them from each other due to the lack of standardization. This issue has largely not been addressed by the protein structure community. RESULTS: Of 472 diastereotopic atom pairs studied from the

Christopher A. Bottoms; Dong Xu

2008-01-01

450

Atom Interferometry  

SciTech Connect

Atom de Broglie wave interferometry has emerged as a tool capable of addressing a diverse set of questions in gravitational and condensed matter physics, and as an enabling technology for advanced sensors in geodesy and navigation. This talk will review basic principles, then discuss recent applications and future directions. Scientific applications to be discussed include measurement of G (Newton's constant), tests of the Equivalence Principle and post-Newtonian gravity, and study of the Kosterlitz-Thouless phase transition in layered superfluids. Technology applications include development of precision gyroscopes and gravity gradiometers. The talk will conclude with speculative remarks looking to the future: Can atom interference methods be used to detect gravity waves? Can non-classical (entangled/squeezed state) atom sources lead to meaningful sensor performance improvements?

Kasevich, Mark (Stanford University)

2008-05-08

451

Microfabricated plastic chips by hot embossing methods and their applications for DNA separation and detection  

Microsoft Academic Search

Design and fabrication of microfluidic devices on polymethylmethacrylate (PMMA) substrates for analytical chemistry and biomedical-related applications using novel microfabrication methods are described. The image of microstructures is transferred from quartz master templates possessing the inverse image of the devices to plastic plates by using hot embossing methods. The microchannels on quartz master templates are formed by the combination of metal

Gwo-Bin Lee; Shu-Hui Chen; Guan-Ruey Huang; Wang-Chou Sung; Yen-Heng Lin

2001-01-01

452

Hot and Spicy versus Cool and Minty as an Example of Organic Structure-Activity Relationships  

NASA Astrophysics Data System (ADS)

There are two classes of substances that activate neural receptors that are involved in temperature perception. Structures of substances found in spices and food that we normally associate with "hot" (or spicy) and "cool" (or minty) flavors are presented and discussed. Functional group similarities within the two groups provide an interesting example of the relationship between molecular structure and molecular function in organic chemistry.

Kimbrough, Doris R.

1997-07-01

453

Role of entrainment in the stabilisation of jet-in-hot-coflow flames  

Microsoft Academic Search

The aim of the research on the Delft jet-in-hot coflow (DJHC) burner is to gain understanding in the interplay of turbulence and chemistry in conditions as encountered in devices operating in flameless combustion mode, and to test the validity of numerical models when applied to these flameless combustion conditions. Datasets on velocities, temperatures and qualitative OH data of several Dutch

E. Oldenhof; M. J. Tummers; E. H. van Veen; D. J. E. M. Roekaerts

2011-01-01

454

Geochemistry and hydrothermal alteration at selected Utah hot springs. Volume 3. Final report  

Microsoft Academic Search

Potentially economic geothermal resources in Utah will likely consist of large volume of hot rock at depth with a circulating ground water medium transferring heat to the surface. The chemistry of the water and the water-rock interaction should provide valuable guides to temperatures in the deep reservoir and the size, if not of the reservoir itself, of the fluid leaks

W. T. Parry; N. Benson; C. D. Miller

1976-01-01

455

Molecular dynamics with atomic transitions and nuclear reactions  

NASA Astrophysics Data System (ADS)

We describe molecular dynamics particle simulations with particles that have internal structure and/or undergo reactions. These calculations give an atomic-scale description of hot plasma based on well-established microphysics and test kinetic theories used to calculate energy exchange and transport in plasma hydrodynamic simulations. The computer experiments can be given detailed diagnostics, without the usual limits of resolution of Laboratory equipment. Typical applications are non-equilibrium atomic kinetics for emission or absorption of X-ray laser radiation by solid targets and/or atomic-scale simulation of hot plasma with fusion reactions, as in inertial fusion ignition experiments.

More, Richard; Wang, Feilu

2013-08-01

456

Sequencing General Chemistry  

NSDL National Science Digital Library

The material in the authors' general chemistry curriculum has been rearranged into a sequence thought to be more logical to students than the traditional sequence. This fresh approach does not radically change course content but rather produces a systemat

Yoblinski, B. J.

2003-03-01

457

Chemistry, Population, Resources.  

National Technical Information Service (NTIS)

Chemistry plays a central role in the global development of the world's human population and their resources. Its effect is exercised primarily through (1) the production of food, (2) public health, and (3) medical practice and drugs. These factors togeth...

M. Calvin

1977-01-01

458

Chemistry with a Peel.  

ERIC Educational Resources Information Center

Presents experiments that introduce natural product chemistry into high school classrooms. In the laboratory activities, students isolate and analyze the oil in orange peels. Students also perform a steam distillation and learn about terpenes. (DDR)

Borer, Londa; Larsen, Eric

1997-01-01

459

Virtual Chemistry Experiments  

NSDL National Science Digital Library

Chemistry applets simulate various experiments, apparatus, and chemical processes. The display and operation of an applet can be controlled by the user through the PARAM options in the APPLET tag and through JavaScript commands.

Blauch, David N.

460

Chemistry with a Peel.  

ERIC Educational Resources Information Center

|Presents experiments that introduce natural product chemistry into high school classrooms. In the laboratory activities, students isolate and analyze the oil in orange peels. Students also perform a steam distillation and learn about terpenes. (DDR)|

Borer, Londa; Larsen, Eric

1997-01-01

461

Chemistry Laboratory Safety Check  

ERIC Educational Resources Information Center

|An accident prevention/safety check list for chemistry laboratories is printed. Included are checks of equipment, facilities, storage and handling of chemicals, laboratory procedures, instruction procedures, and items to be excluded from chemical laboratories. (SL)|

Patnoe, Richard L.

1976-01-01

462

Opportunities in Chemistry.  

National Technical Information Service (NTIS)

Chemistry is a central science that responds to societal needs. It is critical in man's attempts to discover new processes, tap new sources of energy, develop new materials, feed the world's population, improve health and conquer disease, monitor and prot...

1985-01-01

463

Wet Chemistry Instrument Prototype.  

National Technical Information Service (NTIS)

A wet chemistry instrument prototype for detecting amino acids in planetary soil samples was developed. The importance of amino acids and their condensation products to the development of life forms is explained. The characteristics of the instrument and ...

1974-01-01

464

General Chemistry Multimedia Problems  

NSDL National Science Digital Library

General Chemistry Multimedia Problems ask students questions about experiments they see presented using videos and images. The questions asked apply concepts from different parts of an introductory course, encouraging students to decompartmentalize the material.

465

Chemistry and Detective Fiction.  

ERIC Educational Resources Information Center

Describes an interdisciplinary program consisting of two courses. The first course deals with the chemistry of drugs and poisons; the second course focuses on fictional works in which these drugs and poisons are central to the plots. (SK)

Labianca, Dominick A.; Reeves, William J.

1981-01-01

466

Thomas-Fermi equation of state: The hot curve  

SciTech Connect

We derive the high-temperature limit of the equation of state based on the Thomas-Fermi statistical theory of the atom. The resulting ''hot curve'' is in fact the ideal Fermi gas. We expand the thermodynamic properties of this gas in powers of the fugacity and use this expansion to construct a representation of the pressure, accurate to about 0.1%. This representation is compared with the actual theory for aluminum and the ''hot curve'' is found to represent it well over a large region of interest in applications. 10 refs., 3 figs., 1 tab.

Baker, G.A. Jr.; Johnson, J.D.

1989-01-01

467

Effect of Hot Rolling Process on Microstructure and Properties of Low-Carbon Al-Killed Steels Produced Through TSCR Technology  

Microsoft Academic Search

Low-carbon Al-killed hot rolled strips for direct forming, cold rolling, and galvanizing applications are produced from the\\u000a similar chemistry at Ezz Flat Steel (EFS) through thin slab casting and rolling (TSCR) technology. The desired mechanical\\u000a and microstructural properties in hot bands for different applications are achieved through control of hot rolling parameters,\\u000a which in turn control the precipitation and growth

S. K. Paul; U. Ahmed; G. M. Megahed

468

Organic Chemistry Forum  

NSDL National Science Digital Library

ChemWeb's Organic Chemistry Forum bills itself as a "free online club for the organic chemistry community." Users will need to complete a simple online form to obtain membership and access the site. One highlight of this site is free full-text access to Tetrahedron Letters. This rapid publication journal appears weekly. Along with free access to Beilstein Abstracts, the site includes jobs, a conference diary, news, discussion groups, and more.

2005-01-01

469

UCLA: Organic Chemistry Tutorials  

NSDL National Science Digital Library

Steven Hardinger at the Department of Chemistry and Biochemistry at UCLA created these tutorials to assist students with the difficult concepts presented in introductory organic chemistry. Students can find tutorials dealing with acids and bases, carbocations, Lewis dot structures, and more. Within each tutorial, users can find links to a dictionary that adequately explain the unfamiliar terminology. The tutorials include example problems and exercises to challenge users.

Hardinger, Steven

470

Nicotine Smoke Chemistry  

NSDL National Science Digital Library

The featured molecules this month come from the paper Using "Basic Principles" To Understand Complex Science: Nicotine Smoke Chemistry and Literature Analogies by Jeffrey Seeman detailing some of the complexities involved in the volatilization of two alkaloids, nicotine and cocaine. Students could be asked to identify how chemistry is involved in the various steps described in the paper, and most beginning students will be surprised to learn just how complex a process the volatilization of a molecule such as nicotine is.

471

The chemistry of krypton  

Microsoft Academic Search

Krypton is the only noble gas other than xenon to give rise to isolable compounds in macroscopic amounts, although the chemistry of krypton is presently limited to the +2 oxidation state. The strong oxidant-fluorinator properties and thermal instabilities of krypton(II) compounds have posed considerable challenges to determining the extent to which the chemistries of krypton(II) and xenon(II) are analogous. Krypton(II)

John F. Lehmann; Hélène P. A. Mercier; Gary J. Schrobilgen

2002-01-01

472

General Chemistry I  

NSDL National Science Digital Library

From Dr. Michael Bleber of Florida State University's Department of Chemistry, this page contains a virtual guide for a first semester undergraduate course in general chemistry. The site features lecture notes, practice homework, practice exams, homework assignments, useful tables, and a FAQ. The variety and depth of materials at this site make it useful for educators looking for teaching aids, as well as students in search of additional course information.

473

Darwinian evolution and chemistry  

Microsoft Academic Search

Some significant results are collected with a view to ascertain whether a Darwinian chemical evolution is at work in chemistry\\u000a and, if so, to define its specific characters. To this aim prebiotic chemistry, homochirality; chemical reactions and emergence\\u000a of new properties are considered. The Darwinian process of mutation by chance, selection and replication appears to translate\\u000a into chemical exploration of

Gian Paolo Chiusoli

2009-01-01

474

Reformulation in mathematical programming: An application to quantum chemistry  

Microsoft Academic Search

This paper concerns the application of reformulation techniques in mathematical programming to a specific problem arising in quantum chemistry, namely the so- lution of Hartree-Fock systems of equations, which describe atomic and molecular electronic wave functions based on the minimization of a functional of the energy. Their traditional solution method does not provide a guarantee of global optimality and its

Leo Liberti; Carlile Lavor; Nelson Maculan; Marco Antonio Chaer Nascimento

2009-01-01

475

The Chemistry of the Thermal Degradation of Zinc Dialkyldithiophosphate Additives  

Microsoft Academic Search

A mechanism for the thermal decomposition of zinc dialkyldithiophosphate additives has been proposed that accounts for the major degradation products and their dependence on the nature of the alkyl group. The proposed mechanism generally follows well-known rules of phosphorus chemistry. The major points are as follows.(1) The decomposition is initiated by a general migration of alkyl groups from oxygen atoms

R. B. Jones; R. C. Coy

1981-01-01

476

Laboratory studies of the cosmic origins of organic chemistry  

NASA Astrophysics Data System (ADS)

We are constructing a novel merged-beams apparatus to study the cosmic origins of organic chemistry. With this, we plan to measure reaction rate coefficients of atomic C with molecular ions. Such chemical data is important for astrochemical models and observations of cosmic objects.

O'Connor, A. P.; Garrido, M.; Miller, K. A.; Urbain, X.; Savin, D. W.

2012-11-01

477

Hot Talk, Cold Science  

NASA Astrophysics Data System (ADS)

One of the hottest topics in climate science is understanding and evaluating the impacts of possible global warming caused by anthropogenic emissions of greenhouse gases. In Hot Talk, Cold Science, S. Fred Singer does not accept global warming. Singer says in his preface, “The purpose of this book is to demonstrate that the evidence [for global warming] is neither settled, nor compelling, nor even convincing. On the contrary, scientists continue to discover new mechanisms for climate change and to put forth new theories to try to account for the fact that global temperature is not rising, even though greenhouse theory says it should”.

Oglesby, Robert J.

478

Hot suit oven repairs  

SciTech Connect

The Donner-Hanna Coke Plant of Buffalo, New York has four coke oven batteries, the oldest being put into operation in 1943. A description is given of a method of repair developed by the company to repair stack waste heat tunnels and coke oven walls using a firesuit that allowed a repairman to work inside these hot areas. The procedure for the repair of coke oven walls is discussed in detail. A high duty castable was found to simulate the qualities of coke oven silica brick. The repair technique is relatively low cost without the attendant loss of production entailed by other methods of oven repair. (CKK)

Kolvek, R.E.; Bronke, H.R.

1982-01-01

479

Hot cell examination table  

DOEpatents

A table for use in a hot cell or similar controlled environment for use in examining specimens. The table has a movable table top that can be moved relative to a table frame. A shaft is fixedly mounted to the frame for axial rotation. A shaft traveler having a plurality of tilted rollers biased against the shaft is connected to the table top such that rotation of the shaft causes the shaft traveler to roll along the shaft. An electromagnetic drive is connected to the shaft and the frame for controllably rotating the shaft.

Gaal, Peter S. (Monroeville, PA); Ebejer, Lino P. (Weston, MA); Kareis, James H. (Slickville, PA); Schlegel, Gary L. (McKeesport, PA)

1991-01-01

480

Solar hot air system  

SciTech Connect

This solar hot air system is designed to trap and hold heat radiation from the sun, so as to heat one's home and reduce fuel consumption. It consists primarily of a glass, a screen, a collector, and air chambers, the combination of which utilizes two sheets of aluminum to trap and hold heat waves, until removed from the unit. It further includes a powerful small fan, to extract maximum heat from the collector while the sun is shining, and the unit is such, that it may be installed upon a vertical exterior wall, on a sloping roof, or upon a flat roof.

Moore, D.E.; Wiggins, J.W.

1983-04-12

481

Hot air drum evaporator  

DOEpatents

An evaporation system for aqueous radioactive waste uses standard 30 and 55 gallon drums. Waste solutions form cascading water sprays as they pass over a number of trays arranged in a vertical stack within a drum. Hot dry air is circulated radially of the drum through the water sprays thereby removing water vapor. The system is encased in concrete to prevent exposure to radioactivity. The use of standard 30 and 55 gallon drums permits an inexpensive compact modular design that is readily disposable, thus eliminating maintenance and radiation build-up problems encountered with conventional evaporation systems.

Black, Roger L. (Idaho Falls, ID)

1981-01-01

482

The Hot Tub Mystery  

NSDL National Science Digital Library

Roma and Clint Underhill are relaxing after a stressful day in their hot tub with some wine. But tragedy strikes, and the next morning their lifeless bodies are found in the water by their housekeeper. The paramedics who respond to her frantic 911 call pronounce the couple dead at the scene and call in the police to investigate. Developed for use in a lower-level undergraduate course on human physiology, students work through the various parts of this interrupted case to discover the cause of death, and in the process learn about blood pressure regulation.

House, Herbert

2005-01-01

483

Hot Off the Press  

NSDL National Science Digital Library

Environmental Health Perspectives (EHP) , a peer-reviewed environmental health research journal (published by the National Institute of Environmental Health Sciences, part of the National Institutes of Health,) provides the EHP Student Edition for high school and college teachers and their students. Each edition contains news articles that summarize a wide variety of scientific information and original research, which are paired with complementary lessons that introduce students to hot-off-the-press science. This article presents ways to integrate EHP's online content in the classroom.

Schlegel, Barry; Tart, Kimberly T.; Hemminger, Laura; Pitman, Lisa; Hines, Stefani; Stephan, Wendy

2006-10-01

484

Atomic antimatter  

Microsoft Academic Search

The production, storage, and investigation of atomic antimatter is considered. The formation of antihydrogen as well as that of more complex systems are discussed. The main arguments for the production and investigation of these systems are given. Different production scenarios and problems to be solved are examined. Potential experiments are described, in particular those using polarized antiprotons obtained from antihydrogen.

Helmut Poth

1988-01-01

485

Atomic Spectra  

NSDL National Science Digital Library

In this Flash animation the user can view the atomic emission spectra (400-700nm) of eight different elements. A draga