Thermal Analysis Studies on Human Skin and Skin Barrier Modulation by Fatty Acids and Propylene Glycol

The thermal behaviour of human stratum corneum (SC) with various hydration levels was studied using differential thermal analysis DSC within the temperature range of –130 to 120°C. SC containing 20% water, resembling the intact condition, shows thermal transitions at around –20°C (representing water in skin), –10, 40, 70°C (representing skin lipids), 85°C (representing protein-associated lipids) and 100°C (representing skin protein). Dehydration of SC causes the transitions at –20 and 100°C to be invisible. Lipid extraction followed by dehydration eliminates all transitions. Further hydration produces a transition of water at around 0°C with a huge change in enthalpy. The perturbation effects of penetration enhancers fatty acids (FA) and propylene glycol (PG) were studied using DTA on SC after pretreatment with PG alone and FA/PG. The application of PG alone shifted the transitions at 70 and 85°C to lower temperatures. Additionally, the application to dehydrated stratum corneum removes the transitions at –10°C. Saturated fatty acids, e.g. nonanoic and decanoic acids, exert barely noticeable effects on the thermal behaviour of SC suggesting that they easily mix with the skin lipids. Thermal analysis also revealed that the cis-9- and 13-isomers of octadecenoic acid (monounsaturated fatty acids) form a separate domain containing mostly the pure fatty acids within the SC lipids and suppress the lipid transitions at 70/80°C. Polyunsaturated fatty acids linoleic and -linolenic acids — form separate domains but do not completely suppress the SC lipid transitions at 70/80°C as monounsaturated acids do. This study suggests different ways of perturbation by various fatty acids.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effect of electric and magnetic fields on plasma control during CO2 laser welding

Feasibility in using electric and magnetic fields as a plasma control tool during high-power laser welding is explored in this paper. Preliminary results indicated that both fields can influence the shielding effect of the plasma above the keyhole. It was found that at suitable field parameters the penetration depth can be increased by more than 13%. Moreover, under the effect of both fields, the interrelation between the penetration depth and the width of bead was found. In addition, the influence of both electric and magnetic fields strength, field direction and laser power on the penetration depth and the width of bead were also investigated.     

关于最弱受约束电子势模型理论中势函数物理意义的讨论

从屏蔽、贯穿和极化作用考虑,对最弱受约束电子势模型理论（简称WBEPM理论）的势函数进行了讨论。通过一系推导、论证,得出WBEPM理论的有效势的物理意义为：势函数中的第一项表示最弱受约束电子在有效核电荷＋Z′e中心场中的势能;第二项代表最弱受约束电子对非最弱受约束电子和核组成的“实”的极化作用所引起的偶极子场中的势能。     

Extended hybrid pressure and velocity boundary conditions for D3Q27 lattice Boltzmann model

The extended hybrid electronic-ionic, thermal, magnetic, electric and force couple fields pressure and velocity boundary conditions for D3Q27 lattice Boltzmann model is established. Then, the closed-form solutions of extended distribution functions are derived. Last, the Fukushima nuclear plant Cesium-137 penetration case is discussed.     

Space and surface-state effects in multiphoton emission

We investigate multiphoton emission of electrons from solid surfaces in the presence of nonperturbative monochromatic laser fields. We study the dependence of transmission probabilities on surface states, the penetration depth of laser fields in solids and the size of the laser focus in vacuum. To this end we present a one-space-dimensional model which permits to study these problems and develop a numerically stable algorithm for solving the corresponding time-dependent Schrödinger equation.     

Numerical Simulation of Pressure-Swirl Spray Dispersion by Using Eulerian-Lagrangian Method

To gain a general understanding of atomization and sheet breakup processes, the interaction of pressure-swirl hollow-cone sprays and a quiescent medium was investigated computationally. The spray characteristics of Iso-octane (n-C₈H₁₈) with high pressure-swirl injector in the ambient conditions are modeled. The Linearized Instability Sheet Atomization (LISA) model has been used to describe the primary breakup processes of the spray. Sauter Mean Diameter, sheet thickness and exit velocity were computed as the results of primary breakup. Disintegration of large drops is simulated using Taylor analogy breakup (TAB) model in which the Rosin-Rammler distribution is used. Evaporation and collision models are deactivated in this study. The model considers the transient behavior of the pre-spray and steady-state behavior of the main spray for three various injection pressures and liquid mass flow rates. Qualitative and quantitative comparisons between the simulated and experimentally measured results were made. The numerical simulations can successfully demonstrate the spray characteristics, such as spray tip penetration, drop sizes and overall spray structure.     

High rotating speed projectile penetrating into moving vehicle door at different incident angle

This paper uses the numerical simulation LS-DYNA, to simulate the process of the projectile with high rotating speed and different penetration angles penetrating into the moving vehicular door. Because of the moving of the vehicular door, the projectile will turn, and the ballistic trajectory will migrate. At the same time, the projectile will deflect from the vehicular door because of the projectile’s penetration angles. In the process of the penetration, the projectile’s moving speed is 300 m/s; rotating speed is 0 and 6370 r/s. The vehicular door’s moving speed is 80 m/s. The penetration angle is 30°, 45°, 60° and 90°. The projectile is the semi-sphere nose projectile whose diameter is 7.62 mm; the vehicular door’s thickness is 2 mm. The material model is the JOHN-COOK material model that can characterize strain, strain rate hardening and thermal softening effects. Through comparing with the results by simulation to study the effects of the projectile’s final velocity, the angle of rotation, the ballistic trajectory’s migration and the projectile’s deflection with different projectile’s rotating speeds and penetration angles.     

Ion scattering and X-ray photoelectron spectroscopy of copper overlayers vacuum deposited onto mercaptohexadecanoic acid self-assembled monolayers

Metal overlayers deposited in vacuum onto self-assembled monolayer (SAM) systems serve as models for more complex metalized polymers. Metals (M) deposited onto SAMs with different organic functional end groups exhibit a wide range of behavior, ranging from strong chemical interactions with the end group to complete penetration of the metal through the SAM. In this work, we have characterized the interactions of Cu with the ---COOH of mercaptohexadecanoic acid (MHA, HOOC(CH₂)₁₅SH) SAMs self assembled on gold films by using X-ray photoelectron spectroscopy (XPS) to examine the chemical interactions, and a combination of XPS and ion scattering spectroscopy (ISS) to deduce the growth mode and penetration rate of the deposited Cu. We found that submonolayer amounts of Cu react with HOOC, whereas the rest of the Cu remains metallic and penetrates beneath the SAM surface to the SAM  Au interface. Considerable amounts of Cu (5 nm or more) will penetrate beneath the SAM layer, which is ca. 2.5 nm thick, despite the submonolayer presence of Cu at the SAM surface. The penetration rate depends strongly on the Cu deposition rate. Depositing copper onto MHA at 220 K or less, or using faster Cu deposition rates, results in slower or even completely suppressed penetration of the Cu through the SAM layer, whereas exposure to X-rays greatly enhances the penetration rate of large amounts of Cu through the SAM layer. The reacted copper is, based on the XPS 2p and LMM peaks, in the +2 oxidation state, but cannot be identified with a simple, stoichiometric oxide such as Cu₂O, CuO, or Cu (OH)₂.     

Modeling finite thickness slab perforation using a coupled Eulerian–Lagrangian approach

A coupled Eulerian–Lagrangian (CEL) method can be used to model many types of dynamic events. Projectile penetration through solids is particularly well-suited to a CEL method. In this study the CEL method in the commercially-available code Abaqus was used to model a near rigid projectile perforating finite thickness concrete slabs. A near rigid projectile can be modeled as a Lagrangian material with distinct material interfaces, while the solid target can be modeled as an Eulerian material capable of large deformations. An improved concrete constitutive model is also described that was implemented into Abaqus as a user material model. A simplified stochastic model was also implemented to capture some of the heterogeneous nature of concrete. The CEL simulations are compared to experimental data to demonstrate the utility of this method for this type of perforation event.