Although molecular techniques have identified Helicobacter pylori in drinking water-associated biofilms, there is a lack of studies reporting what factors affect the attachment of the bacterium to plumbing materials. Therefore, the adhesion of H. pylori suspended in distilled water to stainless steel 304 (SS304) coupons placed on tissue culture plates subjected to different environmental conditions was monitored. The extent of adhesion was evaluated for different water exposure times, using epifluorescence microscopy to count total cell numbers. High shear stresses-estimated through computational fluid dynamics-negatively influenced the adhesion of H. pylori to the substrata (P < 0.001), a result that was confirmed in similar experiments with polypropylene (P < 0.05). However, the temperature and inoculation concentration appeared to have no effect on adhesion (P > 0.05). After 2 hours, H. pylori cells appeared to be isolated on the surface of SS304 and were able to form small aggregates with longer exposure times. However, the formation of a three-dimensional structure was only very rarely observed. This study suggests that the detection of the pathogen in well water described by other authors can be related to the increased ability of H. pylori to integrate into biofilms under conditions of low shear stress. It will also allow a more rational selection of locations to perform molecular or plate culture analysis for the detection of H. pylori in drinking water-associated biofilms.
Our aim was to evaluate the influence of different application parameters on microtensile bond strength (microTBS) of an "all in one" water-based self-etching primer/adhesive to dentin. Extracted human third molars had their crowns transversally sectioned next to the dentinoenamel junction. Prompt-L-Pop adhesive was applied using five modes: (1) following the manufacturer's instructions (MI); (2) after 36% H(3)PO(4) etching (15 s) (AG); (3) after H(3)PO(4) etching and 5% NaOCl (2 min) with constant agitation (HG); (4) as a double layer (DL); and (5) for double the application time (DT). Resin build-ups were constructed with Tetric Ceram. After storage for 24 h, 6 months, or 12 months in water at 37 degrees C, the specimens were vertically sectioned into beams (cross-sectional areas, 1 mm(2)). Each beam was tested in an Instron Machine at 0.5 mm/min. Analysis of variance and Student-Newman-Keuls were used (P < 0.05). Bonded interfaces were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The highest microTBS values were obtained when AG was used, and the lowest when MI was employed. The HG, DL, and DT modes resulted in similar microTBS values. Water storage reduced microTBS in all groups except the MI group. SEM and TEM revealed hybrid layer and resin tag formation in all groups. Applied after AG, HG, DL, and DT, Prompt L-Pop adhesive provided adequate bond strength to dentin after 24 h of water storage. Bond strength decreased when specimens were stored in distilled water for 6 or 12 months.
Suppressing thoughts often leads to a “rebound” effect, both in waking cognition (thoughts) and in sleep cognition (dreams). Rebound may be influenced by the valence of the suppressed thought, but there is currently no research on the effects of valence on dream rebound. Further, the effects of dream rebound on subsequent emotional response to a suppressed thought have not been studied before. The present experiment aimed to investigate whether emotional valence of a suppressed thought affects dream rebound, and whether dream rebound subsequently influences subjective emotional response to the suppressed thought. Participants (N = 77) were randomly assigned to a pleasant or unpleasant thought suppression condition, suppressed their target thought for 5 min pre‐sleep every evening, reported the extent to which they successfully suppressed the thought, and reported their dreams every morning for 7 days. It was found that unpleasant thoughts were more prone to dream rebound than pleasant thoughts. There was no effect of valence on the success or failure of suppression during wakefulness. Dream rebound and successful suppression were each found to have beneficial effects for subjective emotional response to both pleasant and unpleasant thoughts. The results may lend support for an emotion‐processing theory of dream function.
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