Archive for the ‘researches 4’ Category
Sunday, March 16th, 2008
Redox Chemistry of the Triplet Complex (PNP)Co(I).
Reaction of PNPCo, where PNP is (tBu2PCH2SiMe2)2N-, with the persistent radical galvinoxyl, G, gives PNPCoIIG, a nonplanar S = 3/2 species. Reaction with PhCH2Cl or with 0.5 mol I2 gives PNPCoX (X = Cl or I, respectively), but additional ...
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Sunday, March 16th, 2008
Vapor Pressure and Density of Thermotropic Liquid Crystals: MBBA, 5CB, and Novel Fluorinated Mesogens.
The vapor pressures and densities of six thermotropic liquid crystal-forming molecules (mesogens) have been determined experimentally as functions of temperature. The ubiquitous mesogenic compounds n-(4-methoxybenzylidene)-4-butylaniline (MBBA) and 4\'-cyano-4-n-pentylbiphenyl (5CB), which both exhibit ...
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Sunday, March 16th, 2008
Time-Resolved Studies of Energy Transfer from meso-Tetrakis(N-methylpyridinium-4-yl)- porphyrin to 3,3\'-Diethyl-2,2\'-thiatricarbocyanine Iodide along Deoxyribonucleic Acid Chain.
The excitation energy transfer from meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP) to 3,3\'-diethyl-2,2\'-thiatricarbocyanine iodide (DTTCI) along the deoxyribonucleic acid (DNA) double strand was investigated by the steady-state absorption and fluorescence measurements and time-resolved fluorescence measurements. ...
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Sunday, March 16th, 2008
Ab Initio QM/MM Studies of the Phosphoryl Transfer Reaction Catalyzed by PEP Mutase Suggest a Dissociative Metaphosphate Transition State.
The interconversion between phosphoenolpyruvate (PEP) and phosphonopyruvate (P-pyr) catalyzed by PEP mutase is investigated using an ab initio QM/MM method with the QM region treated at the ...
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Sunday, March 16th, 2008
Thermodynamic Interactions in Double-Network Hydrogels.
Double-network hydrogels (DN-gels) prepared from the combination of a moderately cross-linked anionic polyelectrolyte (PE) and an uncross-linked linear polymer solution (NP) exhibit mechanical properties such as fracture toughness that are intriguingly superior to that of their individual constituents. The scheme of ...
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Sunday, March 16th, 2008
Surfactant-Assisted Alignment of ZnO Nanocrystals to Superstructures.
Self-organization of ZnO nanoparticles into various superstructures (sheet, platelet, ring) has been achieved with the assistance of micelles formed by surfactant cetyltrimethylammonium bromide (CTAB) under one-pot condition. The CTAB-modified zinc hydroxy double salt (Zn-HDS) mesocrystals act as intermediates to ...
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Sunday, March 16th, 2008
Vibrational Energy Relaxation of a Hydrogen-Bonded Complex Dissolved in a Polar Liquid via the Mixed Quantum-Classical Liouville Method.
The vibrational energy relaxation (VER) of the hydrogen stretch in a linear hydrogen-bonded complex dissolved in a polar solvent is studied. The study is based on the Azzouz-Borgis ...
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Sunday, March 16th, 2008
A Differential Fluctuation Theorem.
We derive a nonequilibrium thermodynamics identity (the \"differential fluctuation theorem\") that connects forward and reverse joint probabilities of nonequilibrium work and of arbitrary generalized coordinates corresponding to states of interest. This identity allows us to estimate the free energy difference between domains ...
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Sunday, March 16th, 2008
Coupling of Complex Aromatic Ring Vibrations to Solvent through Hydrogen Bonds: Effect of Varied On-Ring and Off-Ring Hydrogen-Bonding Substitutions.
In this study, we examine the coupling of a complex ring vibration to solvent through hydrogen-bonding interactions. We compare phenylalanine, tyrosine, l-dopa, dopamine, norepinephrine, epinephrine, and hydroxyl-dl-dopa, ...
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Sunday, March 16th, 2008
Theoretical Studies of Solid Bicyclo-HMX: Effects of Hydrostatic Pressure and Temperature.
On the basis of density functional theory (DFT) and molecular dynamics (MD), the structural, electronic, and mechanical properties of the energetic material bicyclo-HMX have been studied. The crystal structure optimized by the LDA/CA-PZ method compares ...
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Sunday, March 16th, 2008
Cooperativity in Intramolecular Bifurcated Hydrogen Bonds: An Ab Initio Study.
Molecular orbital and density functional theory calculations are performed on some di- and tetrasubstituted derivatives of anthraquinone, dihydrophenazine, and acridone to investigate cooperativity in a pair of bifurcated hydrogen bonds occurring in the same molecule. The ...
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Sunday, March 16th, 2008
Heterolytic Bond Dissociation in Water: Why Is It So Easy for C(4)H(9)Cl But Not for C(3)H(9)SiCl?
The recently developed (Song, L.; Wu, W.; Zhang, Q.; Shaik, S. J. Phys. Chem. A 2004, 108, 6017-6024) valence bond method coupled to a polarized continuum model (VBPCM) is used ...
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Sunday, March 16th, 2008
Experimental and Computational Investigation of Gas-Phase Reaction of Chlorine with n-Propanol: Observation of Chloropropanol Conformational Isomerization at Room Temperature.
FTIR smog chamber techniques were used to measure k(Cl+n-C3H7OH) = (1.74 +/- 0.15) x 10-10 and k(Cl+CH2ClCH2CH2OH) = (7.54 +/- 0.73) x 10-11 cm3 molecule-1 s-1 in ...
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Sunday, March 16th, 2008
Use of Effective Core Potential Calculations for the Conformational and Vibrational Study of Platinum(II) Anticancer Drugs. cis-Diamminedichloroplatinum(II) as a Case Study.
In the light of the recognized anticancer properties of cisplatin-type inorganic systems, the exact knowledge of their conformational preferences is of the utmost importance for ...
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Sunday, March 16th, 2008
A Microwave Spectroscopic and Quantum Chemical Study of 3-Butyne-1-selenol (HSeCH(2)CH(2)CCH).
The microwave spectrum of 3-butyne-1-selenol has been studied by means of Stark-modulation microwave spectroscopy and quantum chemical calculations employing the B3LYP/aug-cc-pVTZ and MP2/6-311++G(3df,3pd) methods. Rotational transitions attributable to the H80SeCH2CH2CCH and H78SeCH2CH2CCH isotopologues of two conformers ...
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Sunday, March 16th, 2008
Electronic State Spectroscopy of c-C(5)F(8) Explored by Photoabsorption, Electron Impact, Photoelectron Spectroscopies and Ab Initio Calculations.
The electronic transitions and resonance-enhanced vibrational excitations of octafluorocyclopentene (c-C5F8) have been investigated using high-resolution photoabsorption spectroscopy in the energy range 6-11 eV. In addition, the high-resolution electron energy loss ...
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Sunday, March 16th, 2008
Experimental and Molecular Dynamics Simulation Study of the Sublimation and Vaporization Energetics of Iron Metalocenes. Crystal Structures of Fe(eta(5)-C(5)H(4)CH(3))(2) and Fe[(eta(5)-(C(5)H(5))(eta(5)-C(5)H(4)CHO)].
The standard molar enthalpies of sublimation of ferrocene, 1,1\'-dimethylferrocene, decamethylferrocene, ferrocenecarboxaldehyde and alpha-methylferrocenemethanol, and the enthalpy of vaporization of N,N-dimethyl(aminomethyl)ferrocene, at 298.15 K, were determined ...
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Sunday, March 16th, 2008
A New Scale of Electronegativity Based on Electrophilicity Index.
By calculating the energies of neutral and different ionic forms (M2+, M+, M, M-, and M2-) of 32 elements (using B3LYP/6-311++G** level of theory) and taking energy (E) to be a Morse-like function of the number of ...
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Sunday, March 16th, 2008
Temperature Dependences for the Reactions of O(-) and O(2)(-) with O(2)(a(1)Delta(g)) from 200 to 700 K.
Rate constants and product ion distributions for the O- and O2- reactions with O2(a 1Deltag) were measured as a function of temperature from 200 to 700 K. The measurements were ...
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Sunday, March 16th, 2008
Ultrafast Intramolecular Charge Transfer with Strongly Twisted Aminobenzonitriles: 4-(Di-tert-butylamino)benzonitrile and 3-(Di-tert-butylamino)benzonitrile.
The newly synthesized aminobenzonitriles with two bulky amino substituents 4-(di-tert-butylamino)benzonitrile (DTABN) and 3-(di-tert-butylamino)benzonitrile (mDTABN) have strongly twisted amino groups in the ground state. From X-ray crystal analysis it is found that the amino twist angle ...
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Sunday, March 16th, 2008
Easy Ambient Sonic-Spray Ionization Mass Spectrometry Combined with Thin-Layer Chromatography.
On-spot detection and analyte characterization on thin-layer chromatography (TLC) plates is performed via ambient desorption/ionization and (tandem) mass spectrometry detection, that is, via easy ambient sonic spray ionization mass spectrometry (EASI-MS). As proof-of-principle cases, mixtures of ...
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Sunday, March 16th, 2008
Effects of Ionic Liquid [bmim][PF(6)] on Absorption Spectra and Reaction Kinetics of the Duroquinone Triplet State in Acetonitrile.
The transient absorption spectra and photoinduced electron-transfer process of duroquinone (DQ) in mixed binary solutions of ionic liquid (IL) [bmim][PF6] and acetonitrile (MeCN) have been investigated by laser ...
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Sunday, March 16th, 2008
Parallel Electrophoretic Depletion, Fractionation, Concentration, and Desalting of 96 Complex Biological Samples for Mass Spectrometry.
The preparation of complex biological samples for high-throughput mass spectrometric analyses remains a significant bottleneck, limiting advancement of the capabilities of mass spectrometry (MS) and ultimately limiting development of novel clinical ...
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Sunday, March 16th, 2008
Isolation of Discrete Nanoparticle-DNA Conjugates for Plasmonic Applications.
Discrete DNA-gold nanoparticle conjugates with DNA lengths as short as 15 bases for both 5 and 20 nm gold particles have been purified by anion-exchange HPLC. Conjugates comprising short DNA (<40 bases) and large gold particles (>/=20 nm) ...
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Sunday, March 16th, 2008
Spin-Polarizable Excitonic Luminescence in Colloidal Mn(2+)-Doped CdSe Quantum Dots.
The photoluminescence of colloidal Mn (2+)-doped CdSe nanocrystals has been studied as a function of nanocrystal diameter. These nanocrystals are shown to be unique among colloidal doped semiconductor nanocrystals reported to date in that quantum confinement allows ...
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