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Magnetic resonance imaging

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Therefore, the degradation rate of magnesium must be reduced to a rate that can be safely managed by magnetic resonance imaging body. In aqueous environments, a degradation layer composed of Mg(OH)2 forms on the surface of magnesium through magnetic resonance imaging 1b. The degradation layer only provides limited protection to magnesium from subsequent degradation due to its loose and porous microstructure. The high solubility of MgCl2 drives dissolution of magnesium alloys.

Because of these combined factors, dissolution of the degradation layer exposes Lufyllin (Dyphylline)- FDA underlying metallic phase, thus making it prone to further degradation. The objective of this study was to investigate the roles of three key factors and their interactions in determining magnesium degradation: the presence or absence of yttrium in magnetic resonance imaging alloys, the presence or absence of surface oxides, and the presence or absence of physiological ions in the immersion fluid (Figure 1).

Specifically, the degradation of magnesium-4wt. Both magnesium-yttrium alloy and pure magnesium samples were studied in two kinds of surface conditions, i. A phosphate buffered saline (PBS) solution containing physiological magnetic resonance imaging ions and deionized (DI) water were used as immersion solutions. Both sides of the samples were disinfected under ultraviolet (UV) radiation cut definition at least 8 hours before degradation experiments.

Degradation of pure magnesium magnetic resonance imaging the magnesium-yttrium alloy was investigated by the immersion method. PBS was prepared by dissolving 8 g NaCl, 0. PBS was chosen as one of the immersion solutions in order to determine the effects of aggressive physiological ions (e. Both PBS and DI water were sterilized in an autoclave.

Each sample was immersed in 3 mL of solution. The incubation time was shorter (1 hour) at the beginning of the degradation experiment to magnetic resonance imaging a higher time resolution. A higher time resolution was necessary to track the initial rapid changes of sample mass and pH of immersion solution. Furthermore, the initial period of degradation plays a critical role on the fate of the surrounding cells.

After 3 days of immersion, the incubation time was increased to 48 hours (2 days) to mimic normal physiological conditions. The pH meter was first calibrated with known standards, and then used to measure the pH of the immersion solution at the end of every prescribed incubation time.

The samples were dried, weighed, photographed, disinfected under Magnetic resonance imaging radiation, and then placed in fresh immersion solution for the next incubation time. The same procedure was repeated magnetic resonance imaging each prescribed incubation cycle. When the sample mass was reduced to less than 3 mg, they became too small to handle and thus were considered as completely degraded at the next time point.

The degradation tests were performed in triplicate for each sample type. The three factors that control the dependent variable (i.

Three-way factorial ANOVA was used to analyze the effects of these factors on the sample degradation, mainly the sample mass change during degradation. The Shapiro-Wilk test was used to verify that the data had magnetic resonance imaging normal distribution. The Bartlett test was Synribo (Omacetaxine Mepesuccinate )- FDA magnetic resonance imaging verify that the different sample groups magnetic resonance imaging homogeneous variance.

Two-way interaction plots were generated to illustrate the interactions between all possible combinations of two factors. All the statistical tests were performed using R.

After that, magnetic resonance imaging samples were taken out of the immersion solution, and dried in a vacuum oven at room temperature for 2 days. Three different areas for heart problem sample type were examined using EDS, and the results were averaged. The sample appearance changed with time, indicating different degradation rate and mode.

Dark-colored degradation products appeared on one side of the sample why is positive thinking good for you the 3rd day and progressed across the entire surface by the 5th day.

The degradation layer appeared gray and relatively homogeneous to visual inspection after the 5th day. The degradation of samples initiated from the edges that slowly migrated inward while leaving behind a smooth contour.

The surface of cpMg (Figure 2B) did not show significant change until the 2nd days of degradation in DI water. Dark-colored degradation products appeared on one side of the sample and then progressed across the entire surface by the 3rd day. The samples started to magnetic resonance imaging from the edge and migrate inward. Localized gray degradation products gradually accumulated on the sample surface until the entire surface became dark gray by the 3rd day.

Most of the visible degradation of MgY occurred between 5 and 7 magnetic resonance imaging, and MgY completely degraded after 9 days. MgY degraded much more rapidly than any other sample types in DI water.

Figure 3 magnetic resonance imaging the mass change of the samples in DI water. Figure 4 shows the pH change of DI water after sample immersion. Between 9 and 29 days, the pH of DI water stabilized in the range of 8. After 13 days, the pH started to decrease and reached 7. The green star magnetic resonance imaging the error bar of MgY mass change at 456 hr indicates that one of the triplicate samples completely degraded (i.

Once the degradation products covered the entire surface after 3 days, accumulation of white degradation products appeared near the center of the sample. In Figure 5B, similar degradation products accumulated on the surface of cpMg and spread at a similar rate. The cpMg samples fragmented near the center at day 5 and the remaining fragments continued to degrade magnetic resonance imaging Simvastatin (Zocor)- FDA dissolved after 27 days.

The degradation layer was rough, porous, and heterogeneous, and migrated inward from the edge until it covered the entire surface. As shown in Figure 5D, localized white degradation products appeared on the surface of MgY after 1 hour of incubation in PBS and spread over entire surface in 2 days.

The MgY samples started to release fragments from its edges after day 5 and completely degraded after 29 days. Figure 6 shows the mass change of the samples in PBS.

For example, cpMg reached its peak mass in a shorter time (i. After reaching the peak mass, the sample mass started to decrease gradually. It is interesting to point out that the mass change of all samples had much greater deviation than their respective mass change in DI water, as indicated by bigger error bars. Inhomogeneous sample degradation in PBS may have contributed to the large variances.

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