Role of Monomer Alkyl Chain Length in Pretilt Angle Control of Polymer-Stabilized Liquid Crystal Alignment System

The pretilt angle of liquid crystal (LC) molecules in LC cells was manipulated by adding a mixture of two photocurable monomers, alkyl acrylate and biphenyl diacrylate, into the LCs after the UV treatment. The hexyl acrylate and octadecyl acrylate were applied to examine the alkyl chain length effect on the pretilt angle control under the condition of a fixed concentration of biphenyl diacrylate. The LC alignment was continuously adjusted from homogeneous to homeotropic alignment in the polymer-stabilized LC system by simply increasing the alkyl acrylate concentration in the LCs. At a given molar concentration of alkyl acrylate, the addition of octadecyl acrylate exhibits higher pretilt angle than that of hexyl acrylate. Both the pretilt angle of the LCs and advancing contact angle of water on the inner surfaces of LC cells simultaneously changed due to surface chemical nature and surface roughness. The pretilt angle increases along with an increase in the advancing contact angle. As a consequence, the surface advancing contact angle acts as an index for pretilt angle control

Molecular Dynamics Study on the Growth Mechanism of Methane plus Tetrahydrofuran Mixed Hydrates

Molecular dynamics (MD) simulations are performed to analyze the dominating factors for the growth of CH₄ + THF mixed hydrates, and the results are compared with the growth of single guest CH₄ and THF hydrates. While CH₄ hydrate has a type I crystalline structure, the presence of THF in the aqueous phase results in the growth the type II structure hydrate. Compared to THF hydrates, the presence of CH₄ in the system enhances the dissociation temperature. The growth rate of CH₄ + THF mixed exhibits a maximum value at about 290 K at 10 MPa. The growth rate is found to be determined by two competing factors: (1) the adsorption of CH₄ at the solid–liquid interface, which is enhanced with decreasing temperature, and (2) the migration of THF to the proper site at the interface, which is enhanced with increasing temperature. Above 290 K, which is about 10 K higher than the dissociation temperature of pure THF hydrate, the growth of cage can proceed only when a sufficient amount of CH₄ is adsorbed at the interface. The growth rate is dominated by the uptake of CH₄ at the interface, as in the case of pure CH₄ hydrate. Below 290 K, the growth is not much affected by the presence of CH₄. Instead, the growth rate is determined by the rearrangement of THF molecules at the interface, as in the case of pure THF hydrate

Molecular Dynamics Study on the Equilibrium and Kinetic Properties of Tetrahydrofuran Clathrate Hydrates

Tetrahydrofuran (THF) is an effective promoter of methane hydrates, and itself with water can form clathrate hydrates even without the presence of methane gas. In this work, the stability limit and kinetic properties of THF hydrates were simulated using molecular dynamics (MD) simulations. The change in dissociation temperature of THF hydrates with pressure and concentration of THF in the aqueous phase were well reproduced with MD simulations. The rate of growth of THF hydrates is found to exhibit a maximum value when the liquid-phase THF concentration is about 0.3–0.8 times (depending on temperature) of the THF concentration in the hydrate phase. The existence of some optimal growth concentration explains the preferred lateral growth in experiments. The maximum growth rate is a result of two competing effects: the adsorption of THF molecules to the growing interface, which is the limiting step at low THF concentrations, and the desorption/rearrangement of THF molecules at the interface, limiting step at high THF concentrations. The large cages of structure II (sII) hydrate are fully occupied by THF molecules, regardless of the THF concentration in the aqueous phase, implying a strong stabilization effect of THF molecules to the cage structures of sII hydrates

Predictive Method for the Change in Equilibrium Conditions of Gas Hydrates with Addition of Inhibitors and Electrolytes

Here we present a predictive method for the change in the three-phase (vapor–liquid–hydrate) equilibrium condition of gas hydrates upon the introduction of organic inhibitors and electrolytes. The Peng–Robinson–Stryjek–Vera (PRSV) equation of state, combined with the COSMO-SAC activity coefficient liquid model through the modified Huron–Vidal (MHV1) mixing rule, is used to describe the fluid phase, and the van der Waals and Platteeuw (vdW–P) model is used to describe the hydrate crystalline phase. The temperature-dependent Langmuir absorption constants for the vdW–P model are determined by fitting to the equilibrium condition of pure gas hydrates. Once determined, the method contains no adjustable binary interaction parameters and can be used for prediction of the phase behaviors of gas hydrates with additives that do not enter the cages of the clathrate hydrates (e.g., most inhibitors and electrolytes). We examined the accuracy of this method using five pure gas hydrates, five organic inhibitors, and nine electrolytes, and over ranges of temperature (259.0–303.6 K) and pressure (1.37 × 10⁵–2.08 × 10⁸ Pa). The average relative deviations in the predicted equilibrium temperatures are found to be 0.23% for pure gas hydrates, 0.72% with organic inhibitors, and 0.18% with electrolytes, respectively. We believe that this method is useful for many gas hydrate related engineering problems such as the screening of inhibitors for gas hydrates in flow assurance

Prediction of Phase Equilibrium of Methane Hydrates in the Presence of Ionic Liquids

In this work, a predictive method is applied to determine the vapor–liquid-hydrate three-phase equilibrium condition of methane hydrate in the presence of ionic liquids and other additives. The Peng–Robinson–Stryjek–Vera Equation of State (PRSV EOS) incorporated with the COSMO-SAC activity coefficient model through the first order modified Huron–Vidal (MHV1) mixing rule is used to evaluate the fugacities of vapor and liquid phases. A modified van der Waals and Platteeuw model is applied to describe the hydrate phase. The absolute average relative deviation in predicted temperature (AARD-T) is 0.31% (165 data points, temperature ranging from 273.6 to 291.59 K, and pressure ranging from 1.01 to 20.77 MPa). The method is further used to screen for the most effective thermodynamic inhibitors from a total of 1722 ionic liquids and 574 electrolytes (combined from 56 cations and 41 anions). The valence number of ionic species is found to be the primary factor of inhibition capability, with the higher valence leading to stronger inhibition effects. The molecular volume of ionic liquid is of secondary importance, with the smaller size resulting in stronger inhibition effects

Effect of GW0742 on Electrocardiographic Pattern and Changes.

<p>There was no difference between the vehicle treated group (A) and the GW0742 treated group (B).</p

Changes in Cardiac Performance of STZ Rats treated with/without GW0742 (7.5 mg/kg).

<p>Values (mean±SE) were obtained from each group of eight rats.</p>***<p><i>P</i><0.05 and ***<i>P</i><0.01 for values compared to the control.</p

Effects of GW0742 or Dobutamine on Cardiac Performance in Anesthetized Rats.

<p>The effects of dobutamine and co-administration of GW0742 and/or GSK0660 were investigated in the anesthetized rats. The changes in hemodynamic dP/dt (A), mean blood pressure (MBP) (B) and heart rate (HR) (C) were recorded continuously throughout the whole experiment. All values are presented as mean ± SEM (n = 8). *<i>P</i><0.05, **<i>P</i><0.01 and ***<i>P</i><0.001 compared with the control group.</p

Changes of Developed Pressure and Beat Rate in isolated Rat Heart.

<p>Isolated rat hearts were treated with GW0742 (10⁻⁶ M) with/without GSK0660 (10⁻⁶ M) or with atenolol (10⁻⁶ M) using Dobutamine (10⁻⁶ M) with/without atenolol (10⁻⁶ M) as reference. Values (mean±SE) were obtained from each group of 8 rats.</p>**<p><i>P</i><0.01 and ***<i>P</i><0.01 as compared with the control.</p

Effects of GW0742 and Dobutamine on Cardiac Performance in Hearts Isolated from Rats.

<p>The representative picture shows the change in cardiac performance caused by GW0742 (A) or dobutamine (B) in isolated hearts. Heart rate and cardiac contractility were recorded before and after the perfusion of the test agents.</p