The longevity of resin restorations is currently an area of great interest in adhesive dentistry. However, no work has been conducted to investigate the durability of resin-dentin bond structures ...using human substrate in vivo. The purpose of this study was to investigate the degradation of the resin-dentin bond structures aged in an oral environment for 1, 2, or 3 years. Cavities were prepared in primary molars, and an adhesive resin system (Scotchbond Multi-Purpose) was applied to the cavity. After I to 3 years, following the eruption of the succedaneous permanent teeth, the resin-restored teeth were extracted. Immediately after extraction, those teeth were sectioned perpendicular to the adhesive interface and trimmed to produce an hourglass-shaped specimen. Then, a micro-tensile test was performed at a crosshead speed of 1.0 mm/min. The mean bond strengths were statistically compared with one-way ANOVA and Fisher's PLSD test (p < 0.05). Further, all fractured surfaces were observed by SEM, and the area fraction of failure mode was calculated by means of a digital analyzer on SEM photomicrographs. There were significant differences in tensile-bond strength among all 3 groups (p < 0.05), with mean values ranging from 28.3 ± 11.3 MPa (control), to 15.2 ± 4.4 MPa (1 to 2 years), to 9.1 ± 5.1 MPa (2 to 3 years). Moreover, under fractographic analysis, the proportion of demineralized dentin at the fractured surface in specimens aged in an oral environment was greater than that in control specimens. Furthermore, degradation of resin composite and the depletion of collagen fibrils was observed among the specimens aged in an oral environment. Analysis of the results of this study indicated that the degradation of resin-dentin bond structures occurs after aging in the oral cavity.
Objective
To clarify the effects of uterine myometrial suture techniques at prior caesarean section on the incidence of pathologically diagnosed placenta accreta in placenta praevia with prior ...caesarean section (PPPC).
Design
Case–control study.
Setting
Eleven tertiary referral hospitals in central Japan.
Population
A total of 98 cases of placenta praevia, a history of one or more prior caesarean sections, and a history of uterine transverse incision and usage of only absorbable thread for myometrial sutures at the prior caesarean section. Exclusions were a history of myomectomy or Strassmann's operation.
Methods
Cases were grouped into a pathologically diagnosed placenta accreta group (38 cases) and a no accreta group (60 cases). Clinical characteristics including uterine suture methods at prior caesarean section were compared (single‐layer versus double‐layer closure; continuous versus interrupted sutures in the inner myometrial layer).
Main outcome measure
The incidence of placenta accreta.
Results
No difference was found comparing single‐layer with double‐layer closure in the incidence of placenta accreta (37.1 versus 39.7%, P = 0.805); however, a significant difference was found comparing continuous with interrupted sutures (58.1 versus 29.9%, P = 0.008). Multivariable logistic regression analysis with stepwise selection for the eight factors meeting the criterion of P < 0.10 in univariate analysis was used, and four independent factors were selected, as follows: gravidity ≥ 3 (adjusted odds ratio, aOR, 3.4, 95% confidence interval, 95% CI, 0.99–11.6, P = 0.050); total praevia (versus non‐total, aOR 18.4, 95% CI 3.2–107.0, P = 0.001); anterior/centre placenta (versus posterior, aOR 16.4, 95% CI 3.7–72.2, P < 0.001); and continuous sutures (versus interrupted, aOR 6.0, 95% CI 1.4–25.2, P = 0.015).
Conclusions
In this limited study, a history of continuous sutures on the inner side of the uterine wall showed potential to influence the development of placenta accreta in PPPC patients.
In this report, we studied MgHf co-doped AlN ((Mg,Hf)xA11-xN) aiming for developing an AlN-based dielectric material with the large piezoelectric coefficient. To rapidly screen the wide range of ...composition, we applied combinatorial film growth approach. To get continuous composition gradient on a single substrate, films were deposited on Si (100) substrates by sputtering AlN and Mg-Hf targets simultaneously. Crystal structure was investigated by X-ray diffractometer equipped with a two-dimensional detector (2D-XRD). Composition was determined by Energy Dispersive Spectroscopy (EDS). These studies revealed that we successfully covered the widest ever composition range of 0 < x < 0.24 for this material. In addition, these studies found that we succeeded in realizing largest ever c-axis expansion of 2.7% at x = 0.24, which will lead to the highest enhancement in the piezoelectric coefficient. The results of this study opened the way for high-throughput development of the dielectric materials.
This study discusses novel way of use of ionic liquids to develop Ge-based electrodes for electric double layer capacitors (EDLC). We found that ionic liquids change their electrochemical properties ...depending on the amount of the absorbed water. Wet ionic liquids work as solvents to dissolve Ge and make porous structures, whereas dry ones work as electrolytes of the EDLCs. The former property was used to increase surface area of the electrodes which is desired to increase the capacity of EDLCs. This method showed another advantage in contrast to the dry ionic liquids; wet ones could fill the complex Ge pores in parallel to porous structure formation. Finally, after porous formation, we dried the ionic liquid at 100 °C and prepared the EDLCs composed of Ge porous electrodes. Cyclic voltammetry and impedance measurements indicated that the obtained devices can work as EDLCs.
In this study, we reported on the sputtering growth of the c-axis tilted AlN films, which may have higher electromechanical coupling coefficient k3i than 0001-oriented AlN, on the Si (100) substrates ...in the aim of high output power vibrational energy harvesters (VEHs). We implemented the incident angle deposition in a wide range of temperature from room temperature (RT) to 650°C. At 420°C the c-axis tilted 22°, which is the largest tilt angle reported for the AlN films grown by incident angle deposition. In addition, by changing growth temperature, we succeeded in preparing c-axis tilted AlN films with different tilt angle. Scanning electron spectroscopy (SEM) revealed that the c-axis tilted films have tilted columnar structures which prevents cracks and pinholes going straight through the films. This feature may help avoiding electrical short between electrodes fabricated on top and bottom of the AlN films in VEHs.
We propose a fine-grained stainless-steel as a promising material for a robust oscillator and investigate the dependence of frequency band width, resonance frequency, and output power on initial air ...gaps in electret-based vertical vibration energy harvesters. Beams of the oscillator showed a shallow side-etched depth less than 10 μm, as well as smooth edges. The oscillator succeeded in travelling over 1-mm displacement without fracture. Also, we found that broader frequency band, as well as lower resonance frequency, can be achieved with reducing the initial air gap, whereas the output power exhibited a peak value at an optimal initial air gap. The results may be attributed to the soft spring effect induced by the stronger electrostatic force. Maximum output power density and FWHM of frequency band width of our harvester are 4.7 μW/cm3 and 14 Hz at initial air gap 0.3 mm and acceleration 4.9 m/s2.
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