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Full-Text Articles in Chemistry
Freezing Of Confined Water: A Bilayer Ice Phase In Hydrophobic Nanopores, Kenichiro Koga, Xiao Cheng Zeng, Hideki Tanaka
Freezing Of Confined Water: A Bilayer Ice Phase In Hydrophobic Nanopores, Kenichiro Koga, Xiao Cheng Zeng, Hideki Tanaka
Xiao Cheng Zeng Publications
Molecular dynamics simulations were performed to study the phase behavior of a thin film of water confined to a slit nanopore with smooth walls. A first-order water-to-ice freezing transition has been observed. The resulting ice, which is a crystal of bilayer consisting of rows of distorted hexagons, does not resemble any ice crystals found so far. The confined water contracts upon freezing when the confinement load is low ( ∼0.5 kbar) and expands when the load is high (10 kbar). The residual entropy of the bilayer ice can be calculated exactly, which is about half of the entropy of the …
Coordinate Regulation Of G- And C Strand Length During New Telomere Synthesis, Xinqing Fan, Carolyn Mary Price
Coordinate Regulation Of G- And C Strand Length During New Telomere Synthesis, Xinqing Fan, Carolyn Mary Price
Chemistry Department: Faculty Publications
We have used the ciliate Euplotes to study the role of DNA polymerase in telomeric C strand synthesis. Euplotes provides a unique opportunity to study C strand synthesis without the complication of simultaneous DNA replication because millions of new telomeres are made at a stage in the life cycle when no general DNA replication takes place. Previously we showed that the C-strands of newly synthesized telomeres have a precisely controlled length while the G-strands are more heterogeneous. This finding suggested that, although synthesis of the G-strand (by telomerase) is the first step in telomere addition, a major regulatory step occurs …
Langmuir Monolayers As Disordered Solids: Strain-State Calculations Applied To Stearic Acid, David R. Swanson, Tadeusz Luty, Craig J. Eckhardt
Langmuir Monolayers As Disordered Solids: Strain-State Calculations Applied To Stearic Acid, David R. Swanson, Tadeusz Luty, Craig J. Eckhardt
Craig J. Eckhardt Publications
This paper presents a calculational procedure to determine the equilibrium phase for a given surface pressure π. The monolayer is treated as orientationally free tails grafted to a two-dimensional net formed by the head groups of the amphiphilic molecules. The head groups form a subsystem with translational degrees of freedom characterized by strain variables in the plane of the surface, and the tail groups compose a subsystem characterized by rotational degrees of freedom. The order in the monolayer derives indirectly from the crystalline head groups through translational–rotational coupling. A stress–strain relation is derived which shows the energetically most favorable path …
Scanning Motions Of An Atomic Force Microscope Tip In Water, Kenichiro Koga, Xiao Cheng Zeng
Scanning Motions Of An Atomic Force Microscope Tip In Water, Kenichiro Koga, Xiao Cheng Zeng
Xiao Cheng Zeng Publications
Integral equation techniques are used to study scanning motions of a single-atom tip of the atomic force microscope (AFM) over a rigid, hydrophobic monolayer substrate in water. The calculated force curve is found to be oscillatory, in agreement with recent AFM experiments, which can lead to multiple scanning trajectories for the tip under a constant load. The unique trajectory along which the system is thermodynamically stable is revealed. This study shows that the tip may take a hopping motion over a defect-free substrate due to layering of water molecules between the tip and substrate.
Toward A Molecular Theory Of Vapor-Phase Nucleation. V. Self-Consistency In The Decoupled Dimer Limit, K.J. Oh, Xiao Cheng Zeng, H. Reiss
Toward A Molecular Theory Of Vapor-Phase Nucleation. V. Self-Consistency In The Decoupled Dimer Limit, K.J. Oh, Xiao Cheng Zeng, H. Reiss
Xiao Cheng Zeng Publications
The previous papers of this series introduced a molecular i / υ cluster theory of vapor phase nucleation. This theory differs from most conventional ones in that the cluster (due to fluctuation) is not only characterized by its number of particles i but also by a spherical volume υ. Thus the free energy of formation of the cluster is not merely a one-dimensional function of the number of particles i but a two-dimensional function of both i and v (i.e., it is a free energy surface). In the first stage of this development (Refs. 1–3) the theory is based on …
Solvent-Induced Interactions Between Hydrophobic And Hydrophilic Polyatomic Sheets In Water And Hypothetical Nonpolar Water, Kenichiro Koga, Xiao Cheng Zeng, Hideki Tanaka
Solvent-Induced Interactions Between Hydrophobic And Hydrophilic Polyatomic Sheets In Water And Hypothetical Nonpolar Water, Kenichiro Koga, Xiao Cheng Zeng, Hideki Tanaka
Xiao Cheng Zeng Publications
Hydrophobic and hydrophilic interactions are two major intermolecular forces between hydrophobic nonpolar and hydrophilic polar sites of macromolecules or materials surfaces in solvents. To further understand these two interactions at the microscopic level, an idealized polyatomic model is devised, which includes hydrophobic, hydrophilic, and partially hydrophilic polyatomic planar square molecular sheets. The hydrophobic molecular sheet is composed of the Lennard-Jones particles while the hydrophilic molecular sheet consists of positive and negative charge sites. In the framework of the extended reference interaction site model integral equation theory the solvent-induced interactions (or the potential of mean forces) between two parallel molecular sheets …
Thermal Decomposition Reactions Of Acetaldehyde And Acetone On Si(100), J.L. Armstrong, J.M. White, Marjorie Langell
Thermal Decomposition Reactions Of Acetaldehyde And Acetone On Si(100), J.L. Armstrong, J.M. White, Marjorie Langell
Marjorie A. Langell Publications
We have studied the thermal interactions of acetone and acetaldehyde on Si(100), both sputtered and annealed, using high resolution electron energy loss spectroscopy, (HREELS), x-ray photoelectron spectroscopy (XPS), and temperature programmed desorption (TPD). There is no carbonyl stretch in HREELS and the C and O(1s) XPS peaks reflect two different carbonyl processes, one involving bond cleavage, the other a reduction of the C–O bond order. Hydrogen TPD gives a peak at 840–850 K which is as much as threefold more intense than from H-saturated Si(100). SiO desorbs near 1050 K and XPS shows total loss of oxygen and …
Vapor–Liquid Coexistence Of Quasi-Two-Dimensional Stockmayer Fluids, G.T. Gao, Xiao Cheng Zeng, Wenchuan Wang
Vapor–Liquid Coexistence Of Quasi-Two-Dimensional Stockmayer Fluids, G.T. Gao, Xiao Cheng Zeng, Wenchuan Wang
Xiao Cheng Zeng Publications
A quasi-two-dimensional (2D) Stockmayer model is developed in which the center of mass of the molecule is confined on a plane while the dipole of the molecule can rotate freely in three dimensional space. This model entails essential characteristics of systems such as dipolar molecules physisorbed on a solid surface, or a Langmuir monolayer consisting of short-chain molecules with a dipolar tail. The Gibbs ensemble Monte Carlo technique is employed to determine the vapor– liquid equilibria of the model fluids. An Ewald sum for this quasi-2D model is formulated to account for the long-range dipolar interactions. Three systems with different …
Monte Carlo Simulation Of The Solid To Superliquid Phase Transition Of Langmuir Monolayers. Ii. Characteristics Of Phase Transition, M.D. Gibson, D.R. Swanson, Craig J. Eckhardt, Xiao Cheng Zeng
Monte Carlo Simulation Of The Solid To Superliquid Phase Transition Of Langmuir Monolayers. Ii. Characteristics Of Phase Transition, M.D. Gibson, D.R. Swanson, Craig J. Eckhardt, Xiao Cheng Zeng
Craig J. Eckhardt Publications
The restricted-to-free rotator phase transition of fatty acid monolayers has been modeled using a potential which represents the amphiphiles as planar cross sections of fourfold symmetry. Using much larger system sizes than paper I [D. R. Swanson, R. J. Hardy, and C. J. Eckhardt, J. Chem. Phys. 99, 8194 (1993)], Monte Carlo simulations of the isobaric–isothermal ensemble of model systems with varied number of objects were undertaken to study the effect of system size on the characteristics and order of the phase transition. A peak in the specific heat vs temperature curve was observed near the transition. For each system …