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Articles 301 - 330 of 340

Full-Text Articles in Chemistry

Silole Based Acetylenes As Advanced Π-Conjugated Systems For Optoelectronic Applications, Brian Pagenkopf, Mahmoud M. Abd Rabo Moustafa Dec 2008

Silole Based Acetylenes As Advanced Π-Conjugated Systems For Optoelectronic Applications, Brian Pagenkopf, Mahmoud M. Abd Rabo Moustafa

Chemistry Publications

Nonlinear optical (NLO) and electro-optical (EO) properties of π-conjugated systems have been the subject of intense interest during the past several decades. In this mini-review we focus on semiconducting materials based on alkyne π-conjugation, with particular emphasis on those examples from our laboratory of chromophores containing a silole core. Several closely related examples from the literature are also discussed.

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Synthesis And First X-Ray Structures Of Cobalt(Ii) And Cobalt(Iii) Complexes Bearing 2,4-Dioxo-Alkanoic Acid Dialkylamide Ligands, Brian Pagenkopf, Jian Wang, Nicholas A. Morra, Hongda Zhao, Vincent Lynch, Robert Mcdonald, John F. Reichwein Nov 2008

Synthesis And First X-Ray Structures Of Cobalt(Ii) And Cobalt(Iii) Complexes Bearing 2,4-Dioxo-Alkanoic Acid Dialkylamide Ligands, Brian Pagenkopf, Jian Wang, Nicholas A. Morra, Hongda Zhao, Vincent Lynch, Robert Mcdonald, John F. Reichwein

Chemistry Publications

The aerobic oxidation of 5-hydroxy pentenes to trans-tetrahydrofurans (THFs), the Mukaiyama oxidation, has in recent years emerged as a powerful tool in synthetic chemistry. In this report we describe the first crystal structures of 2,4-dioxo-alkanoic acid dialkylamide complexes for both Co(II) and Co(III) salts. The Co(II) structures show an unprecedented arrangement of atoms, with a central Co(II)(H2O)6 flanked by two Co(II) atoms each coordinated with three anionic chelating ligands. The dimeric Co(III) structures show two anionic chelating ligands and bridging hydroxyl groups.

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Magnetic Properties Of La 0.6 Sr 0.4 Mno 3 Thin Films On Srtio 3 And Buffered Si Substrates With Varying Thickness, A. K. Pradhan, D. Hunter, T. Williams, B. Lasley-Hunter, R. Bah, H. Mustafa, R. Rakhimov, J. Zhang, D. J. Sellmyer, E. E. Carpenter, D. R. Sahu, J. -L. Huang Jan 2008

Magnetic Properties Of La 0.6 Sr 0.4 Mno 3 Thin Films On Srtio 3 And Buffered Si Substrates With Varying Thickness, A. K. Pradhan, D. Hunter, T. Williams, B. Lasley-Hunter, R. Bah, H. Mustafa, R. Rakhimov, J. Zhang, D. J. Sellmyer, E. E. Carpenter, D. R. Sahu, J. -L. Huang

Chemistry Publications

La0.60Sr0.40MnO3 (LSMO) thin films of varying thickness from 12 to 55 nm were deposited using the pulsed-laser deposition technique onto single-crystalline SrTiO3 (STO) and STO-buffered Si substrates. The Tc of LSMO filmsgrown on STO-buffered Si substrates decreases faster than films directly grown on STO with decreasing film thickness. The LSMO/STO film with thickness of 55 nm shows Tc at about 360 K, which is close to the bulk value, whereas TcLSMO film on STO-buffered Si film of similar thickness is reduced to 320 K. This difference is attributed to the strain and interfacial disorders in LSMO film on STO/Si. The …

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Transverse Susceptibility Study Of The Effect Of Varying Dipolar Interactions On Anisotropy Peaks In A Three-Dimensional Assembly Of Soft Ferrite Nanoparticles, Pankaj Poddar, Marienette B. Morales, Natalie A. Frey, Shannon A. Morrison, Everett E. Carpenter, Hariharan Srikanth Jan 2008

Transverse Susceptibility Study Of The Effect Of Varying Dipolar Interactions On Anisotropy Peaks In A Three-Dimensional Assembly Of Soft Ferrite Nanoparticles, Pankaj Poddar, Marienette B. Morales, Natalie A. Frey, Shannon A. Morrison, Everett E. Carpenter, Hariharan Srikanth

Chemistry Publications

Collective magnetization dynamics in nanoparticle assemblies is of current interest as it forms the basis of high density storage media. It is important to understand how interparticle interactions in a three-dimensional (3D) arrangement of superparamagnetic nanoparticles would affect the overall effective magnetic anisotropy of the system. We have studied the influence of varying strengths of dipolar interaction on the static and dynamic magnetic properties of surfactant-coated monodispersed manganese zinc ferrite nanoparticles using reversible transverse susceptibility. We track the evolution of the anisotropy peaks with varying magnetic field, temperature, and interaction strength. The blocking temperature shows an increase from 28 to …

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Poly(D,L-Lactide-Co-Glycolide) Microcomposite Containing Magnetic Iron Core Nanoparticles As A Drug Carrier, Sweta Naik, Everett E. Carpenter Jan 2008

Poly(D,L-Lactide-Co-Glycolide) Microcomposite Containing Magnetic Iron Core Nanoparticles As A Drug Carrier, Sweta Naik, Everett E. Carpenter

Chemistry Publications

Today many potent anticancer drugs like cisplatin are available which carry a number of side effects. A promising way of reducing the side effects is to target the drug to tissue sites by coating it with biocompatible materials like Poly (dl-lactide-co-glycolide) (PLGA) polymer where controlled drug release is achieved during the biodegradation of the polymer. Also the efficacy of anticancer drugs like cisplatin increases at elevated temperatures, so if local heating can be achieved where the drug is targeted. Local heating can be achieved by introducing iron core nanoparticles in the composites along with the drug, which can be heated …

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Total Synthesis Of (+/-)-Goniomitine Via A Formal Nitrile/Donor-Acceptor Cyclopropane [3 + 2] Cyclization., Christian L Morales, Brian L Pagenkopf Dec 2007

Total Synthesis Of (+/-)-Goniomitine Via A Formal Nitrile/Donor-Acceptor Cyclopropane [3 + 2] Cyclization., Christian L Morales, Brian L Pagenkopf

Chemistry Publications

The total synthesis of (+/-)-goniomitine has been accomplished in 17 linear steps with 5.2% overall yield starting from commercially available delta-valerolactam. A synthetic highlight includes the first application of a formal [3 + 2] cycloaddition between a highly functionalized nitrile and a donor-acceptor cyclopropane to prepare an indole nucleus. The use of a microwave reactor is shown to greatly improve the reaction times for two steps.

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Reduction Of Esters To Ethers Utilizing The Powerful Lewis Acid Bf2otf·Oet2, Brian Pagenkopf, Nicholas A. Morra Sep 2007

Reduction Of Esters To Ethers Utilizing The Powerful Lewis Acid Bf2otf·Oet2, Brian Pagenkopf, Nicholas A. Morra

Chemistry Publications

No abstract provided.

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First Total Synthesis And Structural Reassignment Of (-)-Aplysiallene., Jian Wang, Brian L Pagenkopf Aug 2007

First Total Synthesis And Structural Reassignment Of (-)-Aplysiallene., Jian Wang, Brian L Pagenkopf

Chemistry Publications

The first total synthesis of (-)-aplysiallene has been completed in 16 steps and features a key sequential Mukaiyama aerobic oxidative cyclization to prepare the fused bis-THF core. The original stereochemical assignment has been revised as shown.

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C-2/C-3 Annulation And C-2 Alkylation Of Indoles With 2-Alkoxycyclopropanoate Esters., Barbora Bajtos, Ming Yu, Hongda Zhao, Brian L Pagenkopf Aug 2007

C-2/C-3 Annulation And C-2 Alkylation Of Indoles With 2-Alkoxycyclopropanoate Esters., Barbora Bajtos, Ming Yu, Hongda Zhao, Brian L Pagenkopf

Chemistry Publications

The annulation reaction between various indoles and 2-alkoxycyclopropanoate esters is reported. Both high efficiency and complete stereochemical control were observed in some cases with this annulation process. A single stereocenter on the cyclopropane controls the diastereoselective formation of up to four new stereocenters. A different reaction course was observed with 3-substituted indole substrates, and an intervening C-3 to C-2-migration process arose that gives synthetically useful C-2 alkylation indole products.

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Control Of The Cation Occupancies Of Mnzn Ferrite Synthesized Via Reverse Micelles, M. D. Shultz, M. J. Allsbrook, E. E. Carpenter Jan 2007

Control Of The Cation Occupancies Of Mnzn Ferrite Synthesized Via Reverse Micelles, M. D. Shultz, M. J. Allsbrook, E. E. Carpenter

Chemistry Publications

Variations in cation occupancy in mixed metal ferrite systems can affect their electronic and magnetic properties. It is known that different synthesis parameters can lead to various cation distributions and the ability to tune these distributions is of great interest. This study uses the extended x-ray-absorption fine structure–IR relationship to investigate the effect of various Fe2+/Fe3+ ratios in initial synthesis conditions on cation distribution for manganesezincferrite (MZFO). Differences in the precipitated material before firing could lead to differences in the final material if fired under similar conditions. This work uses several different ratios of Fe3+/Fe2+, which will affect the initial …

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Vapor Phase Nucleation On Neutral And Charged Nanoparticles: Condensation Of Supersaturated Trifluoroethanol On Mg Nanoparticles, Victor Abdelsayed, M. Samy El-Shall Jan 2007

Vapor Phase Nucleation On Neutral And Charged Nanoparticles: Condensation Of Supersaturated Trifluoroethanol On Mg Nanoparticles, Victor Abdelsayed, M. Samy El-Shall

Chemistry Publications

A new technique is described to study the condensation of supersaturated vapors on nanoparticles under well-defined conditions of vapor supersaturation, temperature, and carrier gas pressure. The method is applied to the condensation of supersaturated trifluoroethanol (TFE) vapor on Mg nanoparticles. The nanoparticles can be activated to act as condensation nuclei at supersaturations significantly lower than those required for homogeneous nucleation. The number of activated nanoparticles increases with increasing the vapor supersaturation. The small difference observed in the number of droplets formed on positively and negatively charged nanoparticles is attributed to the difference in the mobilities of these nanoparticles. Therefore, no …

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Investigations On The Structure Of Dimethyl Sulfoxide And Acetone In Aqueous Solution, Sylvia E. Mclain, Alan K. Soper, Alenka Luzar Jan 2007

Investigations On The Structure Of Dimethyl Sulfoxide And Acetone In Aqueous Solution, Sylvia E. Mclain, Alan K. Soper, Alenka Luzar

Chemistry Publications

Aqueous solutions of dimethyl sulfoxide (DMSO) and acetone have been investigated using neutron diffraction augmented with isotopic substitution and empirical potential structure refinement computer simulations. Each solute has been measured at two concentrations—1:20 and 1:2 solute:water mole ratios. At both concentrations for each solute, the tetrahedral hydrogen bonding network of water is largely unperturbed, though the total water molecule coordination number is reduced in the higher 1:2 concentrations. With higher concentrations of acetone, water tends to segregate into clusters, while in higher concentrations of DMSO the present study reconfirms that the structure of the liquid is dominated by DMSO-water interactions. …

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Size Dependent Magnetic Properties And Cation Inversion In Chemically Synthesized Mnfe2o4 Nanoparticles, C. N. Chinnasamy, Aria Yang, S. D. Yoon, Kailin Hsu, M. D. Shultz, E. E. Carpenter, S. Mukerjee, C. Vittoria, V. G. Harris Jan 2007

Size Dependent Magnetic Properties And Cation Inversion In Chemically Synthesized Mnfe2o4 Nanoparticles, C. N. Chinnasamy, Aria Yang, S. D. Yoon, Kailin Hsu, M. D. Shultz, E. E. Carpenter, S. Mukerjee, C. Vittoria, V. G. Harris

Chemistry Publications

MnFe2O4nanoparticles with diameters ranging from about 4to50nm were synthesized using a modified coprecipitation method. X-ray diffractograms revealed a pure phase spinel ferrite structure for all samples. Transmission electron microscopy showed that the particles consist of a mixture of both spherical (smaller) and cubic (larger) particles dictated by the reaction kinetics. The Néel temperatures (TN) of MnFe2O4 for various particle sizes were determined by using high temperature magnetometry. The ∼4nm MnFe2O4 particles showed a TN of about 320°C whereas the ∼50nm particles had a TN of about 400°C. The high Néel temperature, compared with the bulk MnFe2O4 TN of 300°C, is …

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Effect Of Field Direction On Electrowetting In A Nanopore, D. Bratko, Christopher D. Daub, Kevin Leung, Alenka Luzar Jan 2007

Effect Of Field Direction On Electrowetting In A Nanopore, D. Bratko, Christopher D. Daub, Kevin Leung, Alenka Luzar

Chemistry Publications

We manifest a significant influence of field direction and polarity on surface wetting, when the latter is tuned by application of an external electric field. Thermodynamics of field-induced filling of hydrocarbon-like nanopores with water is studied by open ensemble molecular simulation. Increased field strength consistently results in water-filling and electrostriction in hydrophobic nanopores. A threshold field commensurate with surface charge density of about one elementary charge per 10 nm2 suffices to render prototypical paraffin surfaces hydrophilic. When a field is applied in the direction perpendicular to the confining walls, the competition between orientational polarization and angle preferences of interfacial water …

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Electrowetting At The Nanoscale, C. D. Daub, D. Bratko, K. Leung, A. Luzar Jan 2007

Electrowetting At The Nanoscale, C. D. Daub, D. Bratko, K. Leung, A. Luzar

Chemistry Publications

Using molecular simulations of nano-sized aqueous droplets on a model graphite surface we demonstrate remarkable sensitivity of water contact angles to the applied electric field polarity and direction relative to the liquid/solid interface. The effect is explained by analyzing the influence of the field on interfacial hydrogen bonding in the nanodrop, which in turn affects the interfacial tensions. The observed anisotropy in droplet wetting is a new nanoscale phenomenon that has so far been elusive as, in current experimental setups, surface molecules represent a very low fraction of the total number affected by the field. Our findings may have important …

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Synthesis Of Indolizines And Benzoindolizines By Annulation Of Donor-Acceptor Cyclopropanes With Electron-Deficient Pyridines And Quinolines, Nicholas A. Morra, Christian L. Morales, Barbora Bajtos, Xin Wang, Hyosook Jang, Jian Wang, Brian Pagenkopf Nov 2006

Synthesis Of Indolizines And Benzoindolizines By Annulation Of Donor-Acceptor Cyclopropanes With Electron-Deficient Pyridines And Quinolines, Nicholas A. Morra, Christian L. Morales, Barbora Bajtos, Xin Wang, Hyosook Jang, Jian Wang, Brian Pagenkopf

Chemistry Publications

The formal [3+2] dipolar cycloaddition (or annulation) of donor-acceptor cyclopropanoate esters with pyridines and 5-nitroquinoline is reported. Electron-deficient pyridine dipolarophiles (R=CN, CO2Et, COMe) participate in the annulation whereas electron rich species do not. The product 2,3-dihydroindolizines undergo rapid autooxidation, and the X-ray structures for two of the aromatic products are reported.

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Reversible Paramagnetism To Ferromagnetism In Transition Metal-Doped Tio2 Nanocrystals Prepared By Microwave Irradiation, Garry Glaspell, Asit B. Panda, M. S. El-Shall Jan 2006

Reversible Paramagnetism To Ferromagnetism In Transition Metal-Doped Tio2 Nanocrystals Prepared By Microwave Irradiation, Garry Glaspell, Asit B. Panda, M. S. El-Shall

Chemistry Publications

TiO2nanoparticlesdoped with 1%, 5%, and 10% M (M=Co, Fe, and Ni) were prepared by microwave irradiation and characterized using x-ray diffraction, transmission electron microscopy, and magnetometry. The as-prepared samples are found to be paramagnetic at room temperature, with the magnetic susceptibility following the Curie-Weiss law in the investigated range of 2–300K. However, transformation from paramagnetism to room-temperature ferromagnetism (RTFM) was observed by hydrogenating the samples at 400°C. Reheating in air converted the samples back to paramagnetic while rehydrogenating the samples again induced ferromagnetism. It is argued that the reversible RTFM observed is due to interaction between the dopant metal ions …

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Orientational Correlations In Liquid Acetone And Dimethyl Sulfoxide: A Comparative Study, Sylvia E. Mclain, Alan K. Soper, Alenka Luzar Jan 2006

Orientational Correlations In Liquid Acetone And Dimethyl Sulfoxide: A Comparative Study, Sylvia E. Mclain, Alan K. Soper, Alenka Luzar

Chemistry Publications

The structure of acetone and dimethyl sulfoxide in the liquid state is investigated using a combination of neutron diffractionmeasurements and empirical potential structure refinement (EPSR) modeling. By extracting the orientational correlations from the EPSR model, the alignment of dipoles in both fluids is identified. At short distances the dipoles or neighboring molecules are found to be in antiparallel configurations, but further out the molecules tend to be aligned predominately as head to tail in the manner of dipolar ordering. The distribution of these orientations in space around a central molecule is strongly influenced by the underlying symmetry of the central …

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Cation Occupancy Determination In Manganese Zinc Ferrites Using Fourier Transform Infrared Spectroscopy, M. D. Shultz, E. E. Carpenter, S. A. Morrison, S. Calvin Jan 2006

Cation Occupancy Determination In Manganese Zinc Ferrites Using Fourier Transform Infrared Spectroscopy, M. D. Shultz, E. E. Carpenter, S. A. Morrison, S. Calvin

Chemistry Publications

The magnetic and electric properties of ferrites are influenced by the cation distribution within the crystalline spinel lattice. Methods such as extended x-ray-absorption fine structure(EXAFS) have been used to determine cation occupancies within the crystalline structure of materials such as manganesezincferrite (MZFO); however, it is not practical to be used for daily analysis. Fourier transform infrared (FTIR)spectroscopy is another technique which has the potential to determine cation occupancy while offering speed and convenience. In the literature it has been demonstrated that in ferrite systems FTIR data can be correlated to cation percentages when comparing tetrahedral (Td) and octahedral (Oh) sites. …

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Optical Susceptibilities Of Supported Indium Tin Oxide Thin Films, Jonathan L. Humphrey, Darius Kuciauskas Jan 2006

Optical Susceptibilities Of Supported Indium Tin Oxide Thin Films, Jonathan L. Humphrey, Darius Kuciauskas

Chemistry Publications

The third-order nonlinear optical susceptibility of indium tin oxide (ITO) thin films on glass substrates, χ(3)ITO, was determined in the near-IR spectral region using degenerate four wave mixing (DFWM)spectroscopy with 100fs laser pulses. A DFWM method for measuring thin films on thick substrates was refined for the characterization of films less than 100nm thick and applied to ∼25nm thick ITO films. It was found that χ(3)ITO is purely electronic at 900–1300nm (11000–7700cm−1) and has a value of (2.16±0.18)×10−18m2V−2. Theχ(3)ITO value reaches (3.36±0.28)×10−18m2V−2 at 1500nm (6700cm−1) due to two-photon absorption by free carriers (electrons). Ultrafast electron relaxation was also observed. The …

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Magnetic And Mossbauer Spectroscopy Studies Of Nanocrystalline Iron Oxide Aerogels, E. E. Carpenter, J. W. Long, D. R. Rolison, M. S. Logan, K. Pettigrew, R. M. Stroud, L. Theil Kuhn, B. Rosendahl Hasen, S. Mørup Jan 2006

Magnetic And Mossbauer Spectroscopy Studies Of Nanocrystalline Iron Oxide Aerogels, E. E. Carpenter, J. W. Long, D. R. Rolison, M. S. Logan, K. Pettigrew, R. M. Stroud, L. Theil Kuhn, B. Rosendahl Hasen, S. Mørup

Chemistry Publications

A sol-gel synthesis was used to produce iron oxide aerogels. These nanocrystalline aerogels have a pore-solid structure similar to silica aerogels but are composed entirely of iron oxides. Mössbauer experiments and x-ray diffraction showed that the as-prepared aerogel is an amorphous or poorly crystalline iron oxide, which crystallized as a partially oxidized magnetite during heating in argon. After further heat treatment in air, the nanocrystallites are fully converted to maghemite. The particles are superparamagnetic at high temperatures, but the magnetic properties are strongly influenced by magnetic interactions between the particles at lower temperatures.

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Thermodynamics Of Folding And Association Of Lattice-Model Proteins, Troy Cellmer, Dusan Bratko, John M. Prausnitz, Harvey Blanch Jan 2005

Thermodynamics Of Folding And Association Of Lattice-Model Proteins, Troy Cellmer, Dusan Bratko, John M. Prausnitz, Harvey Blanch

Chemistry Publications

Closely related to the “protein folding problem” is the issue of protein misfolding and aggregation. Proteinaggregation has been associated with the pathologies of nearly 20 human diseases and presents serious difficulties during the manufacture of pharmaceutical proteins. Computational studies of multiprotein systems have recently emerged as a powerful complement to experimental efforts aimed at understanding the mechanisms of proteinaggregation. We describe the thermodynamics of systems containing two lattice-model 64-mers. A parallel tempering algorithm abates problems associated with glassy systems and the weighted histogram analysis method improves statistical quality. The presence of a second chain has a substantial effect on single-chain …

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Kinetics Of Ion-Induced Nucleation In A Vapor-Gas Mixture, Sergey P. Fisenko, David B. Kane, M. Samy El-Shall Jan 2005

Kinetics Of Ion-Induced Nucleation In A Vapor-Gas Mixture, Sergey P. Fisenko, David B. Kane, M. Samy El-Shall

Chemistry Publications

A general solution for the steady-state ion-induced nucleation kinetics has been derived, considering the differences between ion-induced nucleation and homogeneous nucleation. This solution includes a new effect for nucleation kinetics, the interaction of charged clusters with vapor molecules. Analytical expressions for the ion-induced nucleation rate have been obtained for the limiting cases of high and low thermodynamic barriers. The physical explanation of the so-called sign effect is proposed based on multipole expansion of an electric field of the cluster ion. This theory gives good agreement with experiments and is used to elucidate experimentally observed phenomena.

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Experimental And Theoretical Study Of Benzene (Acetonitrile)(N) Clusters, N=1-4, M. Samy El-Shall, George M. Daly, Douglas Wright Jan 2002

Experimental And Theoretical Study Of Benzene (Acetonitrile)(N) Clusters, N=1-4, M. Samy El-Shall, George M. Daly, Douglas Wright

Chemistry Publications

Well-resolved spectra of benzene–acetonitrile binary clustersBAn, with n=1–4 have been obtained by the (one-color) resonant two-photonionization technique using the benzene’s B2u←A1g 000 and 610 resonances. The spectra reveal a rapid increase in complexity with the number of acetonitrile molecules in the cluster, associated with van der Waal modes and isomeric forms. While only single cluster origins are found for the benzene–acetonitrile (BA) and the BA2clusters, two and four distinct isomers are identified for the BA3 and BA4clusters, respectively. The origins of the BA and BA2clusters are blueshifted with respect to the free benzene molecule by 38 cm−1 and 26 …

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Fluoroalcohols As Nucleating Agents In Supersaturated Vapors: Efficient Clustering With Water In The Vapor Phase, V. Abdalsayed, Y. Ibrahim, M. Rusyniak, M. Rabeony, M. S. El-Shall Jan 2001

Fluoroalcohols As Nucleating Agents In Supersaturated Vapors: Efficient Clustering With Water In The Vapor Phase, V. Abdalsayed, Y. Ibrahim, M. Rusyniak, M. Rabeony, M. S. El-Shall

Chemistry Publications

Fluoroalcohols in small concentrations in the vapor phase display striking enhancing effects on homogeneous nucleation of supersaturated aliphatic alcohols, and on the formation of water clusters by supersonic expansion. The enhanced nucleationeffects are attributed to the surfactant properties of fluoroalcohols, which lower the surface tension of the growing droplets, and therefore lower the barrier to nucleation.

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The Effect Of Carrier Gas Pressure On Vapor Phase Nucleation Experiments Using A Thermal Diffusion Cloud Chamber, D. Kane, S. P. Fisenko, M. Rusyniak, M. S. El-Shall Jan 1999

The Effect Of Carrier Gas Pressure On Vapor Phase Nucleation Experiments Using A Thermal Diffusion Cloud Chamber, D. Kane, S. P. Fisenko, M. Rusyniak, M. S. El-Shall

Chemistry Publications

Recent measurements of critical supersaturations for the vapor phase homogeneous nucleation of several substances using a diffusion cloud chamber technique exhibit a dependence on the pressure of the carrier gas used in the experiments. A model of droplet growth and motion in a diffusion cloud chamber, combined with the density and temperature profiles of the chamber is presented to explain the pressure dependent results. The model demonstrates that at higher carrier gas pressures the growth of the droplets is retarded and the optical scattering signal from the particles is reduced. It is concluded that the observed effect may not result …

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Directed Panspermia. 3. Strategies And Motivations For Seeding Star-Forming Clouds, Michael Noah Mautner Jan 1997

Directed Panspermia. 3. Strategies And Motivations For Seeding Star-Forming Clouds, Michael Noah Mautner

Chemistry Publications

Microbial swarms aimed at star-forming regions of interstellar clouds can seed stellar associations of 10 - 100 young planetary systems. Swarms of millimeter size, milligram packets can be launched by 35 cm solar sails at 5E-4 c, to penetrate interstellar clouds. Selective capture in high-density planetary accretion zones of densities > 1E-17 kg m-3 is achieved by viscous drag. Strategies are evaluated to seed dense cloud cores, or individual protostellar condensations, accretion disks or young planets therein. Targeting the Ophiuchus cloud is described as a model system. The biological content, dispersed in 30 μm, 1E-10 kg capsules of 1E6 freeze-dried microorganisms …

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Termolecular Proton Transfer Reactions Assisted By Ionic Hydrogen Bond Formation: Reactions Of Aromatic Cations With Polar Molecules, George M. Daly, Michael Mautner, Y. B. Pithawalla, M. Samy El-Shall Jan 1996

Termolecular Proton Transfer Reactions Assisted By Ionic Hydrogen Bond Formation: Reactions Of Aromatic Cations With Polar Molecules, George M. Daly, Michael Mautner, Y. B. Pithawalla, M. Samy El-Shall

Chemistry Publications

We present a new method that applies resonant‐two‐photon ionization to generate reactant ions selectively in the source of a high‐pressure mass spectrometer (R2PI‐HPMS) for kinetic and equilibrium studies. Applications to reactions that would be obscured otherwise in a complex system are illustrated in mixtures of benzene with polar solvent molecules (S). We observe a novel type of proton transferreactions from C6H6 +• to two S molecules where S=CH3CN, CH3OH, C2H5OH and CH3COOC2H5, and from C6H5CH3 +• to two …

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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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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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