Bleed-out suppression of silicone rubber by electron beam crosslinking

A silicone rubber with a highly crosslinked surface layer was synthesized by a two-step crosslinking reaction with thermal processing and subsequent electron beam (EB) irradiation. The effect of the EB irradiation on the silicone rubber was evaluated by measuring the volume swelling ratio, shore hardness, tensile breaking strength, and water contact angle of the EB-crosslinked silicone rubber. The silicone rubber was effectively crosslinked as the EB irradiation increased. The optimal EB irradiation dose to form the EB-crosslinked structure in the silicone rubber was 500 kGy. Insufficient EB irradiation does not form a sufficient EB-crosslinked structure, while excessive EB irradiation dose would decompose the silicone rubber. The finer crosslinked structures of the surface layer of the silicone rubber formed by EB irradiation could function as a leak-proof filter to prevent the bleed-out of low-molecular-weight siloxanes inside the silicone rubber. The effect of the type of EB-crosslinking agent on the bleed-out suppression effect was investigated. The bleed-out suppression effect was improved in the following order: no EB-crosslinking agent < ethylene glycol dimethacrylate < silicone diacrylate < trimethylolpropane trimethacrylate (TMPTMA). The thermally and EB-crosslinked silicone rubber with TMPTMA successfully reduced the bleed-out ratio by approximately 60%, compared to the thermally crosslinked silicone rubber without EB irradiation and EB crosslinking agent

Brain-immune interaction accompanying odor-evoked autobiographic memory.

The phenomenon in which a certain smell evokes a specific memory is known as the Proust phenomenon. Odor-evoked autobiographic memories are more emotional than those elicited by other sensory stimuli. The results of our previous study indicated that odor-evoked autobiographic memory accompanied by positive emotions has remarkable effects on various psychological and physiological activities, including the secretion of cytokines, which are immune-signaling molecules that modulate systemic inflammation. In this study, we aimed to clarify the neural substrates associated with the interaction between odor-evoked autobiographic memory and peripheral circulating cytokines. We recruited healthy male and female volunteers and investigated the association between brain responses and the concentration of several cytokines in the plasma by using positron emission tomography (PET) recordings when an autographic memory was evoked in participants by asking them to smell an odor that was nostalgic to them. Participants experienced positive emotions and autobiographic memories when nostalgic odors were presented to them. The levels of peripheral proinflammatory cytokines, such as the tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ), were significantly reduced after experiencing odor-evoked autobiographic memory. Subtraction analysis of PET images indicated that the medial orbitofrontal cortex (mOFC) and precuneus/posterior cingulate cortex (PCC) were significantly activated during experiences of odor-evoked autobiographic memory. Furthermore, a correlation analysis indicated that activities of the mOFC and precuneus/PCC were negatively correlated with IFN-γ concentration. These results indicate that the neural networks including the precuneus/PCC and mOFC might regulate the secretion of peripheral proinflammatory cytokines during the experience of odor-evoked autobiographic memories accompanied with positive emotions

Correlation between peripheral cytokine levels and neuroimaging findings.

<p>(A) Scatter plot showing the correlation between the beta value of the mOFC cluster in the Proust condition and the beta value of the precuneus/PCC cluster in the Proust condition. (B) Scatter plot showing the correlation between the beta value of the precuneus/PCC cluster in the Proust condition and IFN-γ concentration after smelling a nostalgic odor that evoked an autobiographic memory. (C) Scatter plot showing the correlation between the beta value of the mOFC cluster in the Proust condition and IFN-γ concentration after smelling a nostalgic odor that evoked an autobiographic memory.</p

Psychological and plasma cytokine data.

<p>(A) Differences in the rating scores for the characteristics of control and nostalgic odors. **p < 0.01 and *p < 0.05 vs. control, paired <i>t</i> test. (B) Differences in the plasma concentration of cytokines (IL-2, IL-4, IL-6, IL-10, TNF-α, and IFN-γ) between control and nostalgic odors. **p < 0.01 and *p < 0.05 vs. control, paired <i>t</i> test.</p