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Articles 30271 - 30300 of 34560

Full-Text Articles in Physical Sciences and Mathematics

Synthesis And Characterization Of A New Class Of Μ3-Oh-Bridged Trimers That Contain Octahedrally Coordinated Divalent Metal Ions Bridged By Three Acetate Ligands And A Unique Catecholate Ligand. Solid State Molecular Structures Of The [(Py)5mii3(Oac)3(Μ3-Oh)((Cat)] Complexes (M = Mn(Ii), Fe(Ii), Co(Ii), Ni(Ii)), R.A. Reynolds, Edward Yu, W.R. Dunham, D. Coucouvanis Jan 1996

Synthesis And Characterization Of A New Class Of Μ3-Oh-Bridged Trimers That Contain Octahedrally Coordinated Divalent Metal Ions Bridged By Three Acetate Ligands And A Unique Catecholate Ligand. Solid State Molecular Structures Of The [(Py)5mii3(Oac)3(Μ3-Oh)((Cat)] Complexes (M = Mn(Ii), Fe(Ii), Co(Ii), Ni(Ii)), R.A. Reynolds, Edward Yu, W.R. Dunham, D. Coucouvanis

Edward Yu

The synthesis and structural characterization of a new class of “basic” trinuclear acetate clusters with solely divalent metal ions and a central μ3-OH ligand are reported. These molecules with the [(py)5MII3(OAc)3(μ3-OH)(cat)] stoichiometry (M = Mn, Fe, Co, Ni) are X-ray isomorphous and isostructural and contain octahedrally coordinated metal ions. The core consists of an antiferromagnetically coupled M3 unit with the metals arranged in the corners of an isosceles triangle. Two of the M−M distances vary between 2.98 and 3.16 Å, and the longer M−M distance is observed between 3.65 and 3.76 Å. As expected from the relative ionic radius lengths, …

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The Temperature Dependence Of Ultra Violet Sulfur Dioxide Absorption Cross Sections, Alexis Brunner Jan 1996

The Temperature Dependence Of Ultra Violet Sulfur Dioxide Absorption Cross Sections, Alexis Brunner

Honors Theses, 1963-2015

Atmospheric sulfur dioxide data became available in 1982 during and after the eruption of El Chichon, when the Total Ozone Mapping Spectrometer, TOMS, received increased absorption in the shortest wavelength channels of the instrument. TOMS was designed to map the daily global total ozone field. The increased absorption was later determined to be due to sulfur dioxide because it is a gaseous volcanic substituent that has corresponding absorption to that seen in the TOMS data. Currently there is no way to develop an algorithm that will accurately subtract the effects of sulfur dioxide from the TOMS data in order to …

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Gas Chromatographic Isolation Of Individual Compounds From Complex Matrices For Radiocarbon Dating, Ti Eglinton, Li Alueihare, Je Bauer, Erm Druffel, Ap Mcnichol Jan 1996

Gas Chromatographic Isolation Of Individual Compounds From Complex Matrices For Radiocarbon Dating, Ti Eglinton, Li Alueihare, Je Bauer, Erm Druffel, Ap Mcnichol

VIMS Articles

This paper describes the application of a novel, practical approach for isolation of individual compounds from complex organic matrices for natural abundance radiocarbon measurement. This is achieved through the use of automated preparative capillary gas chromatography (PCGC) to separate and recover sufficient quantities of individual target compounds for C-14 analysis by accelerator mass spectrometry (AMS). We developed and tested this approach using a suite of samples (plant lipids, petroleums) whose ages spanned the C-14 time scale and which contained a variety of compound types (fatty acids, sterols, hydrocarbons), Comparison of individual compound and bulk radiocarbon signatures for the isotopically homogeneous …

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Mile-A-Minute Weed, (Polygonum Perfoliatum L.), An Invasive Vine In Natural And Disturbed Sites, J. Douglas Oliver Jan 1996

Mile-A-Minute Weed, (Polygonum Perfoliatum L.), An Invasive Vine In Natural And Disturbed Sites, J. Douglas Oliver

Faculty Publications and Presentations

Polygonum perfoliatum L. (Polygonaceae) or mile-a-minute weed, from eastern Asia, has been spreading through wild and disturbed areas of the mid-Atlantic United States. It has a wide ecological amplitude and is found on stream banks, moist thickets, roadsides, nurseries, wood-piles, clearings, and ditches. Polygonum perfoliatum presents serious problems for reforestation because it thrives where forests are clear-cut. A southward direction of spread indicates that the species will probably proliferate in at least some southern states. Mechanical control is not likely to be completely effective because seeds are often left behind. No appropriate biocontrols are known. The plant poses a threat …

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Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓtₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James Jan 1996

Neutron Diffraction And Magnetic Studies Of Nd₂Fe₁₇₋ₓtₓ (T=Si, Mn) Alloys, William B. Yelon, Z. Hu, Mingxing Chen, H. Luo, F. Pourarian, Peter C. Ezekwenna, G. K. Marasinghe, K. H. J. Buschow, D. P. Middleton, William Joseph James

Physics Faculty Research & Creative Works

We have carried out neutron and magnetic studies on Nd2Fe17-xTx (T=Si, Mn) alloys. the unit cell of the compounds contracts with both Si and Mn substitution. Si atoms avoid the 6c site, prefer the 18h site strongly, fill the 9d site steadily and fill the 18f site only at relatively high Si concentration. Mn atoms avoid the 9d sites but prefer the 6c site strongly, while the 18f site and 18h site fill slowly. the Si site occupancies appear to be dominated by the crystal environment while the Mn site occupancies are dominated by steric …

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Carbon Monoxide Amongst Other Chemicals (Presentation), Donald H. Stedman Jan 1996

Carbon Monoxide Amongst Other Chemicals (Presentation), Donald H. Stedman

Fuel Efficiency Automobile Test Publications

No abstract provided.

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Epa Overestimates The Benefit Of Biennial Inspection And Maintenance, Donald H. Stedman Jan 1996

Epa Overestimates The Benefit Of Biennial Inspection And Maintenance, Donald H. Stedman

Fuel Efficiency Automobile Test Publications

The United States Environmental Protection Agency (EPA) computer model of mobile source emissions is used to estimate the benefits of future emissions control programs. Four input assumptions are discussed, each of which tends to overestimate the benefits of biennial testing programs. The assumptions are: each model year drives the same number of miles; high/superemitters, absent initially, increase linearly with mileage; inspection and maintenance (I/M) readings are invariant, and I/M repairs last forever. States opting for these programs should be aware that the predicted benefits may not materialize.

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An Nmr Investigation Of The Effect Of Hydrogen Bonding On The Rates Of Rotation About The C-N Bonds In Urea And Thiourea, Karl A. Haushalter, Janice Lau, John D. Roberts Jan 1996

An Nmr Investigation Of The Effect Of Hydrogen Bonding On The Rates Of Rotation About The C-N Bonds In Urea And Thiourea, Karl A. Haushalter, Janice Lau, John D. Roberts

All HMC Faculty Publications and Research

The interaction between urea and tetrabutylammonium acetate was investigated in dimethylformamide/ dimethyl sulfoxide solutions using ¹H and 15^N NMR. The chemical-shift behavior of the urea protons is consistent with a urea-acetate hydrogen-bonded complex involving both carboxylate oxygens and the urea hydrogens trans to the carbonyl oxygen with K_assoc = 120 ± 10. Line shape analysis of the temperature-dependent ¹H NMR spectra show that ∆G^‡ for rotation about the C-N bond of urea changes only slightly from 11.0 ± 0.1 to 11.2 ± 0.1 kcal/mol on 1:1 molar addition of tetrabutylammonium acetate to a dilute solution of urea. A parallel investigation …

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A Convenient Synthesis Of L-Α-Vinylglycine From L-Homoserine Lactone, David B. Berkowitz, Marianne K. Smith Jan 1996

A Convenient Synthesis Of L-Α-Vinylglycine From L-Homoserine Lactone, David B. Berkowitz, Marianne K. Smith

David Berkowitz Publications

A procedure for the synthesis ofL-IX-vinylglycine from L-homoserine lactone is described. The route developed is convenient (only one chromatography step is required) and efficient (72 %; ≥ 95 % optical yield over 4 steps). Key features include the use of acid-labile protecting groups for the amino (Boc) and carboxyl (diphenylmethyl ester) groups, and the use of the phenylselenolate equivalent derived from sodium borohydride and diphenyl diselenide for L-homoserine lactone cleavage.

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Structures, Thermochemistry, And Electron Affinities Of The Pfn And Pfn- Series, N=1-6, Gregory S. Tschumper, Justin T. Fermann, Henry F. Schaefer Jan 1996

Structures, Thermochemistry, And Electron Affinities Of The Pfn And Pfn- Series, N=1-6, Gregory S. Tschumper, Justin T. Fermann, Henry F. Schaefer

Chemistry Faculty Research & Creative Works

A quantum mechanical study of the phosphorus fluorides and their singly charged anions was carried out. A range of density functional methods was used. Optimized geometries, adiabatic electron affinities, vertical electron affinities, vertical detachment energies, and stabilities toward the loss of a single fluorine atom or fluorine ion are reported. These properties were evaluated exhaustively using four exchange-correlation functionals: Becke's 1988 exchange functional with the correlation functional of Lee, Yang, and Parr, Becke's 1988 exchange functional with the 1986 correlation functional of Perdew, Becke's three parameter Hartree-Fock/density functional hybrid exchange functional with the correlation functional of Lee, Yang, and Parr …

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Sixth International Symposium On Chiral Discrimination, Daniel W. Armstrong Jan 1996

Sixth International Symposium On Chiral Discrimination, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

No abstract provided.

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Enantiomeric Composition And Prevalence Of Some Bicyclic Monoterpenoids In Amber, Daniel W. Armstrong, Eve Y. Zhou, Janusz Zukowski, Barbara Kosmowska-Ceranowicz Jan 1996

Enantiomeric Composition And Prevalence Of Some Bicyclic Monoterpenoids In Amber, Daniel W. Armstrong, Eve Y. Zhou, Janusz Zukowski, Barbara Kosmowska-Ceranowicz

Chemistry Faculty Research & Creative Works

Among the more prevalent chiral monoterpenoid compounds in conifers are α-pinene, β-pinene, and smaller amounts of camphene and limonene. The most prevalent chiral monoterpenoid compounds in fossilized resin (referred to as amber in this paper) appear to be borneol, isoborneol, and camphene. Most of these compounds have easily measured enantiomeric excesses. The borneol and isoborneol in some amber samples have pronounced enantiomeric excesses despite the fact that they are tens of millions of years old. The enantiomeric ratios of the monoterpenoids in different ambers vary tremendously and often are distinct. However, in any single amber sample, the stereochemistry (absolute configuration) …

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Capillary Electrophoretic Enantiomeric Separations Using The Glycopeptide Antibiotic, Teicoplanin, Kimber L. Rundlett, Mary P. Gasper, Eve Y. Zhou, Daniel W. Armstrong Jan 1996

Capillary Electrophoretic Enantiomeric Separations Using The Glycopeptide Antibiotic, Teicoplanin, Kimber L. Rundlett, Mary P. Gasper, Eve Y. Zhou, Daniel W. Armstrong

Chemistry Faculty Research & Creative Works

Teicoplanin is the third in a series of macrocyclic glycopeptide antibiotics that has been evaluated as a chiral selector in capillary electrophoresis (CE). It was used to resolve over 100 anionic racemates at low selector concentrations. Like the other related glycopeptide antibiotics, its enantioselectivity tends to be opposite to that of the ansa-type antibiotics which prefers cationic compounds-particularly amines. Factors that affect teicoplanin-based enantioseparations include the selector concentration, pH, and the concentration of the organic modifier. The temperature and the nature and strength of the buffer are also known to affect the stability of the chiral selector as well as …

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Oxidation States And Magnetism Of Fe Nanoparticles Prepared By A Laser Evaporation Technique, B. J. Jönsson, T. Turkki, V. Ström, M. S. El-Shall, K. V. Rao Jan 1996

Oxidation States And Magnetism Of Fe Nanoparticles Prepared By A Laser Evaporation Technique, B. J. Jönsson, T. Turkki, V. Ström, M. S. El-Shall, K. V. Rao

Chemistry Publications

Nanoparticles of iron and iron oxide have been prepared in a thermal diffusion cloud chamber using pulsed laser evaporation. SEM/TEM studies of these particles reveal a size distribution with a mean diameter of about 60 Å. This is consistent with the mean particle size estimated from the magnetic data. The oxidation levels of these nanoparticles prepared at different partial oxygen pressures were investigated using FTIR. All the samples are found to exhibit superparamagnetism with blocking temperatures ranging from 50 K to above room temperature. Magnetic anisotropy constants are calculated from the frequency dependence of the blocking temperatures are found to …

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A Monte Carlo Study Of Methanol Clusters (Ch3oh)N, N=5-256, D. Wright, M. S. El-Shall Jan 1996

A Monte Carlo Study Of Methanol Clusters (Ch3oh)N, N=5-256, D. Wright, M. S. El-Shall

Chemistry Publications

The thermodynamic and structural properties of methanol clusters (CH3OH) N , N=5–15, 20, 30, 60, 128, 256 and the bulk liquid have been investigated using Monte Carlo simulation. Calculated properties as a function of size include electrostatic and dispersive contributions to the configurational energy, configurational heat capacities,fractal dimension, density profiles, order parameters characterizing dipole and bond vector orientation, and the Lindemann index. The clusterheat capacities as a function of N possess an interior maximum near N=128 and converge to the bulk value from above. Monocyclic, semiplanar structures are found to persist at liquidlike temperatures up to …

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Preparation Of Trifluoromethyl Lactol Derivatives Via Base Initiated Cyclobutanol Ring Opening To A Laterally Lithiated Trifluoromethyl Ketone, Daniel Becker, Daniel L. Flynn Jan 1996

Preparation Of Trifluoromethyl Lactol Derivatives Via Base Initiated Cyclobutanol Ring Opening To A Laterally Lithiated Trifluoromethyl Ketone, Daniel Becker, Daniel L. Flynn

Chemistry: Faculty Publications and Other Works

Benzocyclobutenone derivatives 4 are converted to the corresponding trifluoromethylcyclobutanols 5 by treatment with trifluoromethyltrimethylsilane in the presence of tetra-n-butylammonium fluoride. These trifluoromethylcyclobutanol derivatives are then treated with LiTMP in the presence of aromatic aldehydes to afford trifluoromethyllactols 6 via a laterally-lithiated trifluoromethylketone intermediate.

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Reducibility And A New Entropic Term In Multifragment Charge Distribution, A. Ferrero, I. Iori, A. Moroni, F. Petruzelli, R. Scardaoni, L. G. Moretto, D. R. Bowman, M. Bruno, P. Buttazzo, L. Celano, N. Colonna, M. D'Agostino, J. D. Dinius, M. L. Fiandri, E. Fuschini, C. K. Gelbke, T. Glasmacher, F. Gramegna, D. O. Handzy, D. Horn, W. C. Hsi, M. Huang, G. J. Kunde, M. A. Lisa, W. G. Lynch, P. F. Mastinu, P. M. Milazzo, G. V. Margagliotti, C. P. Montoya, Graham F. Peaslee, L. Phair, R. Rui, C. Schwarz, M. B. Tsang, G. Vannini, C. Williams Jan 1996

Reducibility And A New Entropic Term In Multifragment Charge Distribution, A. Ferrero, I. Iori, A. Moroni, F. Petruzelli, R. Scardaoni, L. G. Moretto, D. R. Bowman, M. Bruno, P. Buttazzo, L. Celano, N. Colonna, M. D'Agostino, J. D. Dinius, M. L. Fiandri, E. Fuschini, C. K. Gelbke, T. Glasmacher, F. Gramegna, D. O. Handzy, D. Horn, W. C. Hsi, M. Huang, G. J. Kunde, M. A. Lisa, W. G. Lynch, P. F. Mastinu, P. M. Milazzo, G. V. Margagliotti, C. P. Montoya, Graham F. Peaslee, L. Phair, R. Rui, C. Schwarz, M. B. Tsang, G. Vannini, C. Williams

Faculty Publications

The charge distributions and their dependence on fragment multiplicity have been studied for the multifragmentation of 30 MeV/nucleon Xe+Au, Cu. For both targets, the charge distributions are approximately independent of the fragment multiplicity n. However, a residual systematic dependence on n is detectable at the largest values of the total charge multiplicity Nc. Such n dependence obeys a simple scaling law and suggests the presence of an entropic term possibly related to the mechanism of multifragmentation. Thermal scaling between the different bins of Nc seems to occur.

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Evaporation Residue, Fission Cross Sections, And Linear Momentum Transfer For 14n Induced Reactions From 35a To 155a Mev, A. A. Sonzogni, A. Elmaani, C. Hyde-Wright, W. Jiang, D. Prindle, R. Vandenbosch, J. Dinius, G. Cron, D. Bowman, C. K. Gelbke, W. Hsi, G. Lynch, C. Montoya, Graham F. Peaslee, C. Schwarz, M. B. Tsang, C. Williams, R. De Souza, D. Fox, T. Moore Jan 1996

Evaporation Residue, Fission Cross Sections, And Linear Momentum Transfer For 14n Induced Reactions From 35a To 155a Mev, A. A. Sonzogni, A. Elmaani, C. Hyde-Wright, W. Jiang, D. Prindle, R. Vandenbosch, J. Dinius, G. Cron, D. Bowman, C. K. Gelbke, W. Hsi, G. Lynch, C. Montoya, Graham F. Peaslee, C. Schwarz, M. B. Tsang, C. Williams, R. De Souza, D. Fox, T. Moore

Faculty Publications

Differential cross sections for evaporation residues and fission fragments for 35A, 100A, 130A and 155A MeV N14 on targets ranging from Sm154 to Au197 have been measured. The angle-integrated cross sections are larger than what might be expected. The fission fragment-fission fragment folding angle correlations for 35A, 100A MeV N14 and 25AMeV O16 on similar targets were also measured. The average linear momentum transfer has been deduced from both the fission angle correlation and from the fore-aft asymmetry of the fission angular distributions in the laboratory system. The data are all consistent with a picture where pre-equilibrium particle emission removes …

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Galvanostatic Pulse And Pulse Reverse Plating Of Zinc-Nickel Alloys From Sulfate Electrolytes On A Rotating Disc Electrode, Branko N Popov, M. Ramasubramanian, S. N. Popova, Ralph E. White, K-M. Yin Jan 1996

Galvanostatic Pulse And Pulse Reverse Plating Of Zinc-Nickel Alloys From Sulfate Electrolytes On A Rotating Disc Electrode, Branko N Popov, M. Ramasubramanian, S. N. Popova, Ralph E. White, K-M. Yin

Faculty Publications

Galvanostatic pulse and pulse reverse techniques have been used to study the plating of zinc–nickel alloys in the presence of nonyl phenyl polyethylene oxide. The effects of average current density, rotation speed of disc electrode and the presence of nonyl phenyl polyethylene oxide in the electrolyte on deposition of zinc–nickel alloys were evaluated. Zinc–nickel plating bath solution chemistry was studied by determining the equilibrium concentrations at various pH levels. It was found that the alloy composition was determined by solution equilibria, mass transfer of the electroactive species within the diffusion layer and by the surface coverage of nonyl phenyl polyethylene …

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1,1′-Diketone And 1,1′-Dinitrile Derivatives Of 2,2′-Biimidazole, Paula M. Secondo, William M. Barnett, Harvest L. Collier, Russell G. Baughman Jan 1996

1,1′-Diketone And 1,1′-Dinitrile Derivatives Of 2,2′-Biimidazole, Paula M. Secondo, William M. Barnett, Harvest L. Collier, Russell G. Baughman

Chemistry Faculty Research & Creative Works

The crystal structures of 2,2′-biimidazole-1,1′-diacetone, C12H14N4O2, and 2,2′-biimidazole-1,1′-diacetonitrile, C10H8N6, have been determined. Both molecules crystallize with coplanar rings having substituents in a trans disposition with a center of inversion located midway between the bridging C atoms.

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Remote Marine Aerosol In The Gulf Of Maine: An Sem Study, Eric S. Gordon Jan 1996

Remote Marine Aerosol In The Gulf Of Maine: An Sem Study, Eric S. Gordon

Honors Theses

Eight aerosol samples were collected from a height of 34 meters atop Petit Manan Light located 16 miles East of Bar Harbor, Maine between July 25, 1995 and August 1, 1995. Both coarse and fine fractions were collected on 8.0 and 0.2 micron polycarbonate membrane filters, respectively. The sampling station consisted of a sampling box as well as a weather station (with various instruments) to record weather data for help in the analysis. The samples were analyzed using a scanning electron microscope and energy dispersive x-ray spectroscopy. Cluster analysis was perforned on the particles, grouping particles together with similar chemical …

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Bromobis(Diethyldithiocarbamato)(4-Methoxyphenyl)Tellurium(Iv), Steinar Husebye, Thoralf Engebretsen, Martin D. Rudd, Sergey V. Lindeman Jan 1996

Bromobis(Diethyldithiocarbamato)(4-Methoxyphenyl)Tellurium(Iv), Steinar Husebye, Thoralf Engebretsen, Martin D. Rudd, Sergey V. Lindeman

Chemistry Faculty Research and Publications

The crystals of the TeIV complex p-CH3OC6H4Te(Et2NCS2)2Br are isomorphous with those of the the iodine and mixed iodine/bromine analogues previously investigated. The structure is pentagonal bipyramidal at the Te atom with four S atoms [Te-S 2.618-2.721 (1) Å] and the Br atom [Te-Br 2.943 (1) Å] in equatorial positions. The p-methoxyphenyl group is axial [Te-C 2.147 (3) Å]. The second axial position is approached by a Br atom of a centrosymmetrically related complex [TeBr 3.423 (1) Å, C-TeBr 173.1 (1)°] so that the molecules are …

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Bromobis(Dimethyldithiocarbamato)(4-Methoxyphenyl)Tellurium(Iv) Dichloromethane Hemisolvate, P-Meoc6H4Te(Me2Ncs2)2Br.0.5ch2Cl2, Steinar Husebye, Steffen Kudis, Sergey V. Lindeman Jan 1996

Bromobis(Dimethyldithiocarbamato)(4-Methoxyphenyl)Tellurium(Iv) Dichloromethane Hemisolvate, P-Meoc6H4Te(Me2Ncs2)2Br.0.5ch2Cl2, Steinar Husebye, Steffen Kudis, Sergey V. Lindeman

Chemistry Faculty Research and Publications

The structure of the title TeIV complex, C13H19BrN2OS4Te.045(CH2Cl2), is pentagonal bipyramidal with four S atoms [Te-S 2.623 (1)-2.717 (1) Å] and the Br atom [Te-Br 2.890 (1) Å] in equatorial positions. The p-methoxyphenyl group is axial [Te-C 2.145 (3) Å] and the second axial position seems to be occupied by a dithiocarbamate group of a neighbouring molecule acting as a -ligand [TeC 3.751 (3) Å, C-TeC 170.2 (1)°], so that molecules are joined into centrosymmetric associations by this secondary coordination.

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Characterization Of Ground And Excited Electronic State Deprotonation Energies Of Systems Containing Double Bonds Using Natural Bond Orbital Analysis, J. K. Badenhoop, Steve Scheiner Jan 1996

Characterization Of Ground And Excited Electronic State Deprotonation Energies Of Systems Containing Double Bonds Using Natural Bond Orbital Analysis, J. K. Badenhoop, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

Natural bond orbital analysis is applied to the ground and excited states of a set of neutral, cationic, and anionic doubly bonded species HnC=XHn (X=C, N, O) isoelectronic with ethylene. The character of the excitation is correlated with calculated charge shifts and geometry changes upon relaxation. For these planar molecules, depopulation of the π bond or population of the π∗ antibond causes an out‐of‐plane twist or pyramidalization upon relaxation correlated to the amount of charge shift. These nonplanar distortions generally lower the energy more than changes in bond lengths and angles. Population of a σXH∗ …

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Characterization Of Ground And Excited Electronic State Deprotonation Energies Of Systems Containing Double Bonds Using Natural Bond Orbital Analysis, J. K. Badenhoop, Steve Scheiner Jan 1996

Characterization Of Ground And Excited Electronic State Deprotonation Energies Of Systems Containing Double Bonds Using Natural Bond Orbital Analysis, J. K. Badenhoop, Steve Scheiner

Steve Scheiner

Natural bond orbital analysis is applied to the ground and excited states of a set of neutral, cationic, and anionic doubly bonded species HnC=XHn (X=C, N, O) isoelectronic with ethylene. The character of the excitation is correlated with calculated charge shifts and geometry changes upon relaxation. For these planar molecules, depopulation of the π bond or population of the π∗ antibond causes an out‐of‐plane twist or pyramidalization upon relaxation correlated to the amount of charge shift. These nonplanar distortions generally lower the energy more than changes in bond lengths and angles. Population of a σXH∗ …

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Effects Of Electron Irradiation And Percent Composition On The Glass Transition Temperature And Damping Of Boron-Epoxy Composites, Ian Ivan Nieves Jan 1996

Effects Of Electron Irradiation And Percent Composition On The Glass Transition Temperature And Damping Of Boron-Epoxy Composites, Ian Ivan Nieves

Dissertations, Theses, and Masters Projects

No abstract provided.

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[(Co)H(Pph3)2-Arachno-Osb3h8], Nigam Rath, J. Bould, L. Barton Jan 1996

[(Co)H(Pph3)2-Arachno-Osb3h8], Nigam Rath, J. Bould, L. Barton

Chemistry & Biochemistry Faculty Works

A single-crystal X-ray diffraction study of the species 2-carbonyl2-hydrido-trans-2,2-bis(triphenylphosphine)-2-osma-arachno-tetraborane confirms the structure as a tetraborane(10) butterfly with a trans-[(CO)H(PPh3)2Os] group replacing a BH2 group at a wing-tip or 2-position. It is compared with the previously reported ruthenaborane analogue (CO)H(PPh3)2-arachno-RuB3H8.

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Condensation Of Supersaturated Vapors Of Hydrogen Bonding Molecules: Ethylene Glycol, Propylene Glycol, Trimethylene Glycol, And Glycerol, David B. Kane, M. Samy El-Shall Jan 1996

Condensation Of Supersaturated Vapors Of Hydrogen Bonding Molecules: Ethylene Glycol, Propylene Glycol, Trimethylene Glycol, And Glycerol, David B. Kane, M. Samy El-Shall

Chemistry Publications

The critical supersaturations required for the homogeneous nucleation (rate of 1 drop cm−3 s−1) of ethylene glycol, propylene glycol, trimethylene glycol and glycerol vapors have been measured over wide temperature ranges (e.g., 280–400 K) using an upward thermal diffusion cloud chamber. At lower temperatures the experimental nucleation rates are much higher than the predictions of the classical nucleation theory. Glycerol shows the best agreement between experiment and theory in the temperature range of 340–370 K. An apparent increase in the critical supersaturation of glycerol is observed with increasing carrier gas (helium) pressure and this effect is more …

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Space-Based Genetic Cryoconservation Of Endangered Species, Michael Noah Mautner Jan 1996

Space-Based Genetic Cryoconservation Of Endangered Species, Michael Noah Mautner

Chemistry Publications

Genetic materials of endangered species must be maintained, for cryoconservation, permanently near liquid nitrogen temperatures below 77 K. Due to the instability of human institutions, permanent safety is best provided at storage sites that maintain passively the needed low temperatures, and provide barriers to access. The required conditions are available in permanently shaded polar lunar craters with equilibrium temperatures of 8 to 40 K, on the moons of Saturn, and unshielded storage satellites. A genetic depository can be incorporated readily into planned lunar programmes.

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Microhollow Cathode Discharges, K. H. Schoenbach, R. Verhappen, R. Tessnow, F. E. Peterkin, W. W. Byszewski Jan 1996

Microhollow Cathode Discharges, K. H. Schoenbach, R. Verhappen, R. Tessnow, F. E. Peterkin, W. W. Byszewski

Bioelectrics Publications

The current–voltage characteristics of hollow cathode discharges and their predischarges in argon under dc and pulsed conditions were found to have a positive slope at pressures up to approximately 50 Torr, and currents up to 20 mA, at a hole diameter of 0.7 mm. In this range of pressure and current, parallel operation of hollow cathode discharges, without ballast, was demonstrated. Scaling to higher pressure is possible by reducing the hole diameter. Pulsed experiments with an array of cathode rings of 75 μm diameter allowed us to obtain parallel operation of more than 50 discharges at a pressure of 350 …

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