Search

Objectives: The aim of this study was to investigate variations in the interaction between enamel, that is, the acquired enamel pellicle (AEP) and citric or hydrochloric acid. Materials and Methods: A 24-h AEP was formed on natural enamel specimens (n = 40) from pooled whole mouth human saliva. Samples were randomly allocated to citric (0.3%, pH 3.2) or hydrochloric (HCl) acid (0.01 M, pH 2.38) exposure for 30 or 300 s. The total protein concentration (TPC), and phosphorous and calcium concentrations of the pellicle were determined before and after acid exposure, and again after re-immersion in saliva. Surface roughness and tandem scanning confocal microscopy imaging were used to assess enamel changes. Results: After 300 s of citric acid exposure, the mean ± SD TPC reduced from 5.1 ± 1.1 to 3.5 ± 1.1 mg/mL (p < 0.05). In contrast, after 300 s of HCl exposure, the mean TPC did not reduce significantly from baseline (6.6 ± 1.1 to 5.7 ± 0.7 mg/mL) but was significantly reduced in the reformed pellicle to 4.9 ± 1.2 mg/mL (p < 0.001). This reduction occurred after significant release of calcium and phosphorous from the enamel surface (p < 0.001). Thirty seconds of exposure to either acid had no obvious effect on the AEP. The surface roughness of the enamel decreased after acid exposure but no differences between groups was observed. Conclusions: These findings indicate that citric acid interacted with proteins in the AEP upon contact, offering enamel protection. In contrast, HCl appeared to bypass the pellicle, and reduced protein was observed only after changes in the enamel chemical composition.

Background. Vascular adventitia contains progenitor cells and is shown to participate in vascular remolding. Progenitor cells are recruited into the venous thrombi in mice to promote neovascularization. We hypothesized that the adventitial progenitor cells of human great saphenous vein (HGSV-AdPC) enhance the resolution of venous thrombosis via neovascularization. Methods. Human great saphenous vein (HGSV) was harvested from the patients with great saphenous vein varicose and sectioned for immunohistochemistry, or minced for progenitor cell primary culture, or placed in sodium dodecyl sulfate solution for decellularization. Human venous thrombi were collected from patients with great saphenous vein varicose and superficial thrombophlebitis. Infrarenal abdominal aorta of New Zealand white rabbits was replaced with interposing decellularized vessel, and the patency of the grafts was confirmed by ultrasonic examination. Animal venous thrombi in the left infrarenal vena cava of mice were produced with Prolene suture ligation and ophthalmic force clipping of this portion. After HGSVs were digested by collagenase, the CD34+CD117+ HGSV-AdPC were isolated on FACS system, labelled with CM-Dil, and transplanted into the adventitia of infrarenal vena cava of nude mice. The percentage of thrombus organization area to the thrombus area was calculated as the organization rate. The thrombus cell, endothelial cells, and macrophages in the thrombi were counted in sections. Cell smears and frozen sections of human saphenous veins and venous thrombi were labeled with Sca1, CD34, CD117, Flk1, CD31, and F4/80 antibodies. The CD34+CD117+ HGSV-AdPC were cultured in endothelial growth medium with vascular endothelial growth factor (VEGF) to induce endothelial cell differentiation and analyzed with real time-PCR, Western blotting, and tube formation assays. Results. Immunohistochemical staining showed that the CD34+CD117+ cells were located within the adventitia of HGSVs, and many CD34+ and CD117+ cells have emerged in the human venous thrombi. The number of progenitor cells within the marginal area of 7 days mice thrombi was shown to be Sca1+ ≈21%, CD34+ ≈12%, CD117+ ≈9%, and Flk1+ ≈5%. Many CD34+adventitial progenitor cells have migrated into the decellularized vessels. FACS showed that the number of CD34+CD117+ HGSV-AdPC in primary cultured cells as 1.2 ± 0.07 % . After CD34+CD117+HGSV-AdPC were transplanted into the adventitia of nude mice vena cava with venous thrombi, the organization rate, nucleate cell count, endothelial cells, and macrophage cells of thrombi were shown to be significantly increased. The transplanted CD34+CD117+ HGSV-AdPC at the adventitia have crossed the vein wall, entered the venous thrombi, and differentiated into endothelial cells. The CD34+CD117+ HGSV-AdPC in the culture medium in the presence of VEGF-promoted gene and protein expression of endothelial cell markers in vitro and induced tube formation. Conclusions. HGSV-AdPC could cross the vein wall and migrate from the adventitia into the venous thrombi. Increased HGSV-AdPC in the adventitia has enhanced the resolution of venous thrombi via differentiating into endothelial cells of neovascularization.

Fractional derivative is increasingly being deployed to improve existing mathematical models due to its unique capability in describing anomalous behavior and memory effects which are common characteristics of natural phenomena. Improved vibration analysis has been accomplished by introducing fractional derivatives to model viscoelastic damping and vibration propagation through complex media and much research has been carried out to date. However, much of these existing research efforts have been sporadic to the best and there remains a pressing need to develop a consistent and systematic theoretical framework for vibration analysis of fractional systems to synergize for more productive and coordinated efforts in the area. This paper seeks to address some fundamental issues to facilitate further development such as the definition of general form of a fractional vibration system, its eigenvalue problem and methods of solution, definition of frequency response functions and applicability of conventional modal analysis, equivalent eigensystem and its more efficient eigensolution. With these important issues being resolved to clear the myth, vibration studies of fractional systems can be encouraged and expected to grow in a more fruitful direction. New methods developed and concepts discussed in the paper have all been validated through realistic numerical case studies based on a practical GARTEUR structure with viscoelastic supports modeled using fractional derivatives.

There is a pressing need in very small scale three‐dimensional (3D) inkjet printing to control and reduce agglomeration, as agglomeration often leads to nozzle clogging. While agglomeration within ultraviolet ink has been studied, there has been, to our knowledge, no extensive studies conducted for surface agglomeration of the ink on nozzle's wall. This numerical study therefore focuses on investigating if surfactants can effectively control surface agglomeration during nanodroplet formation. Many‐body dissipative particle dynamics is the numerical method of choice here. We found that small amount of surfactant of about 1 wt % is sufficient to effectively reduce ink deposition on the nozzle's wall. However, by using the properties of a commercially available surfactant, sodium dodecyl sulfate, it was found that the maximum reduction achieved by its addition is only 60%. Thus, further physical or chemical deagglomeration techniques are required, and we show that by considering these other techniques, reduction of surface agglomeration to nearly 92% can be achieved. Finally, we found that adding surfactants has the additional benefit of improving total kinetic energy of the ink compositions, lowering possibility of agglomerations within the ink. It also raises the nanodroplet velocity while reducing nanodroplet breakup time, which can help speed up the process of 3D printing process. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1615–1624