Investigation of corrosion products formed on the surface of carbon steel exposed in Banda Aceh's atmosphere.

This research aims to study the corrosion rate and characteristics of corrosion products of carbon steel due to exposure in the environment of Banda Aceh, Indonesia. The ASTM G50 was used as the basis for the specifications of the specimens for corrosion rate calculation. The corrosion rate was calculated based on ASTM G1. The features of corrosion products studied are morphological features, types, and chemical compounds of the rust. These characteristics were identified using scanning electron microscopy (SEM) and x-ray diffractometer (XRD). The corrosion rate of carbon steel was obtained using the weight-loss method. The study was conducted for twelve months, i.e. January to December of 2018. After one year of exposure, it was found that the highest corrosion rate occurred in the March-April period which was 0.024 mpy and falls into outstanding category of relative corrosion resistance. Various morphological features of corrosion products found during the period of exposure, including worm nest, bird's nest, globular, cotton ball, laminar, lath, bar, needle-shaped, and whisker structures. These structures were lepidocrocite (γ-FeOOH) and goethite (α-FeOOH). During twelve months of exposure, corrosion products formed were dominantly lepidocrocite and goethite. It was found that the lepidocrocite might transform into goethite through prolonged exposure time.

Evaluation of Ventilation-Induced Lung Inflammation Through Multi-Scale Simulations.

Ventilation-induced lung injury is a common problem faced by patients with respiratory problems who require mechanical ventilation (MV). This injury may lead to a greater chance of developing or exacerbating the acute respiratory distress syndrome which further complicates the therapeutic use of MV. The chain of events begins with the MV initiating an immune response that leads to inflammation induced tissue material alteration (stiffening) and eventually the loss of lung resistance. It is clear from this sequence of events that the phenomenon of ventilation induced injury is multi-scale by nature and, hence, requires holistic analysis involving simulations and informatics. An effective approach to this problem is to break it down into several major physical models. Each physical model is developed separately and can be seen as a component in a larger system that comprises the scale of the problem being investigated. In this paper, a multi-scale system consisting of breathing mechanics, tissue deformation, and cellular mechanics models is developed to assess the immune response. To demonstrate the potential of the model, a fluid-solid model is employed for breathing mechanics, a plane-strain elasticity model is applied to assess tissue deformation, and a cellular automata (CA) model is developed to account for immune response. A case study of three lower airways is presented. The CA model shows that this increased the immune response by five times, which correlates with alteration in the tissue microstructure. This alteration in turn is reflected in the material constant value obtained in the tissue mechanics model. However, the changes in strain rates in the airways after inflammation (and hence, lung compliance) were not as significant as the rates of change in immune response. Finally, results from the fluid-solid model demonstrate its potential for airflow characterization caused by tissue deformation that could lead to disease identification.

Strain-induced inflammation in pulmonary alveolar tissue due to mechanical ventilation.

Inflammation is the body's attempt at self-protection to remove harmful stimuli, including damaged cells, irritants, or pathogens and begin the healing process. In this study, strain-induced inflammation in pulmonary alveolar tissue under high tidal volume is investigated through a combination of an inflammation model and fluid structure interaction (FSI) analysis. A realistic three-dimensional organ model for alveolar sacs is built, and FSI is employed to evaluate strain distribution in alveolar tissue for different tidal volume (TV) values under the mechanical ventilation (MV) condition. The alveolar tissue is treated as a hyperelastic solid and provides the environment for the tissue constituents. The influence of different strain distributions resulting from different tidal volumes is investigated. It is observed that strain is highly distributed in the inlet area. In addition, strain versus time curves in different locations through the alveolar model reveals that middle layers in the alveolar region would undergo higher levels of strain during breathing under the MV condition. Three different types of strain distributions in the alveolar region from the FSI simulation are transferred to the CA model to study population dynamics of cell constituents under MV for different TVs; 200, 500 and 1000 mL, respectively. The CA model results suggests that strain distribution plays a significant role in population dynamics. An interplay between strain magnitude and distribution appears to influence healing capability. Results suggest that increasing TV leads to an exponential rise in tissue damage by inflammation.