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Purpose: To evaluate the effect of pre-treatment air abrasion of surfaces using bioactive glass 45S5 on the progression of erosion in bovine enamel induced by a common soft drink.Materials and Methods: Twelve intact bovine incisors were selected and 24 enamel samples were prepared and randomly assigned to two groups (n = 12): 1. control group, no anti-erosive treatment; 2. experimental group: samples were air abraded with bioglass 45S5 before the erosive challenge. The enamel samples were submitted to erosive cycling using a common soft drink. Enamel surface loss was evaluated using optical profilometry; surface microhardness and roughness changes were determined using Vickers method and Vertical Scanning Interferometry, respectively. In addition, SEM observations and EDS analysis were performed to detect any alterations in surface morphology and mineral content. The data were statistically analysed using one-way ANOVA and Tukey's post-hoc test at a significance level of α = 0.05.Results: The experimental group exhibited less (18.7%) surface loss than did the control group (p < 0.05), while also presenting a statistically significantly smaller decrease in surface microhardness compared to the control group after erosive cycling (p < 0.05). However, neither group showed a statistically significant change in surface roughness (p > 0.05). After the treatments, changes in surface morphology and mineral content of enamel were observed.Conclusions: Surface pre-treatment using air abrasion bioglass 45S5 may help prevent enamel erosion induced by excessive consumption of soft drinks. Further clinical trials are needed to confirm the effectiveness of this method and its clinical significance. [ABSTRACT FROM AUTHOR]

Purpose: The purpose was to investigate the alterations in surface properties of different resin‐matrix CAD/CAM ceramics following tooth brushing simulation (TBS) and compare them with a direct resin composite and a glass ceramic CAD/CAM material. Materials and methods: Four resin‐based CAD/CAM restoratives (Brilliant Crios—BR, Lava™ Ultimate—LV, Grandio Blocs—GR and Shofu Block HC—SH), a leucite‐reinforced glass ceramic (IPS Empress® CAD—EC) and a resin composite (Filtek™ Z250—FZ) for direct restorations were tested. In particular, surface loss, hardness, roughness and morphology were investigated utilizing confocal microscopy, scanning electron microscopy and nanoindentation tester. TBS was conducted for 4 × 15 min on the surface of the samples and then the changes in their surface properties were evaluated. Results: After TBS, all the experimental groups exhibited surface loss to different extent. FZ and BR presented the highest surface loss, while EC and GR the lowest (p < 0.05). Regarding surface roughness, all the tested materials exhibited increase after TBS (p < 0.05), except LV (p = 0.099). EC presented the lowest Sa values, while FZ and BR the highest (p < 0.05). Changes in surface morphology were in compliance with the results of surface roughness and also surface hardness was correlated with surface loss. Conclusions: The tested resin‐matrix CAD/CAM ceramic restorative materials showed a competent behavior against abrasive forces applied during TBS. Surface loss and roughness changes were material dependent and superior compared to a resin composite for direct restorations, while in comparison with a leucite‐reinforced glass ceramic exhibited inferior properties. Clinical significance: Tooth brushing affected differently the surface of the tested restorative materials. However, the abrasive wear that was induced was negligible. Clinical studies are necessary to ascertain if there is clinical significance of these surface alterations that may demand repair of such restorations. [ABSTRACT FROM AUTHOR]

The aim of this research was to evaluate the abrasive dentin wear that can be induced by three commercial whitening toothpastes following a tooth-brushing simulation (TBS) corresponding to a three-month period. Sixty human canines were selected, and the roots were separated from the crowns. Then the roots were randomly divided into six groups (n = 10) and were submitted to TBS using the following slurries: Group 1—deionized water (RDA = 5); Group 2—ISO dentifrice slurry (RDA = 100); Group 3—a regular toothpaste (RDA = 70); Group 4—a charcoal-containing whitening toothpaste; Group 5—a whitening toothpaste containing blue covasorb and hydrated silica; and Group 6—a whitening toothpaste containing microsilica. Following TBS, surface loss and surface roughness changes were evaluated using confocal microscopy. Additionally, surface morphology and mineral content changes were observed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The deionized water group presented the lowest surface loss (p < 0.05), while the charcoal-containing toothpaste presented the highest surface loss, followed by ISO dentifrice slurry (p < 0.001). Blue-covasorb-containing and regular toothpastes did not present statistically significant differences (p = 0.245), and neither didmicrosilica-containing toothpaste or ISO dentifrice slurry (p = 0.112). The surface height parameters and surface morphology changes of the experimental groups followed the surface loss patterns, while no differences were detected in mineral content after TBS.Although the charcoal-containing toothpaste exhibited the highest abrasive wear to dentin, according to ISO 11609, all the tested toothpastes exhibited appropriate abrasive behavior towards dentin. [ABSTRACT FROM AUTHOR]

The rainfall intensity, slope, and underground pore density are major factors affecting the soil erosion of maize‐covered karst slopes. We studied the erosion process of maize‐covered karst slopes and the influencing mechanism of soil erosion on these slopes under different rainfall intensities, slopes, and underground pore density via simulated rainfall tests. The results are as follows: (1) No runoff was observed on the slope surface under light rainfall (30 mm hr−1); instead, subsurface flow was predominant. However, runoff from the surface and subsurface flows under moderate rainfall (60 mm hr−1) increased with the rainfall intensity. The average surface runoff under extreme rainfall (90 mm hr−1) was 2.3‐times that under moderate rainfall. In addition, the average subsurface runoff under extreme rainfall was 1.6‐ and 3.5‐times that under moderate rainfall and light rainfall, respectively. The total amounts of surface and subsurface soil losses increased as the rainfall intensity increased. The surface and subsurface soil losses from light to moderate and extreme rainfall events increased by 258% and 151%, respectively. The soil loss from the surface was 5.3‐times greater than that from the subsurface, indicating that the erosion of maize‐covered karst slopes mainly occurs on the surface and that the subsurface loss is relatively small. (2) As the slope angle increased, the runoff, sediment yield, and proportion of erosion on the surface increased, and vice versa. (3) The subsurface runoff and sediment yield increased as the underground pore density increased, while the opposite occurred on the surface. Multiple regression analysis showed that the rainfall intensity is the most critical factor affecting the soil erosion of maize ‐covered slopes in karst areas, followed by the slope, while the influence of the underground pore density is small. [ABSTRACT FROM AUTHOR]

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Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present systematic review with a network meta-analysis (NMA) aimed to evaluate the effect of high-power lasers, associated or not with fluoride compounds, to control and prevent Erosive Tooth Wear (ETW). The review was registered in the PROSPERO (CRD42021242547) and followed the PICO question: P (population): enamel and dentin substrate; I (Intervention): high-power laser irradiation, associated or not with fluoride compounds; C (Control): no-treatment; and O (Outcomes): prevention/control of ETW. The electronic databases PubMed, Scopus, and EMBASE were searched. Two independent reviewers evaluated in vitro and in situ studies. The risk of bias was assessed using the RoBDEMAT tool. The estimated treatment effect derived from direct and indirect comparisons were analyzed and the difference between these effects was calculated based on the data of enamel and dentin surface loss (in μm). A total of 179 studies were retrieved and after the exclusion of duplicates, 103 studies had their titles and abstracts evaluated. Thirty-nine studies had their full text analyzed for data extraction (Cohen Kappa = 0.88). For sound enamel, the laser irradiation (L), fluoride application (F) and, the association of treatments (L + F) promoted higher protection than No-Treatment (NT). For eroded enamel, L + F and F did not differ, but both treatments reduced surface loss compared to NT and L. For sound and eroded dentin, treatments with laser increased surface loss. Although a high-power laser has some potential to prevent erosive tooth wear, this effect is not better than that of standard fluoride. The use of laser in the management of dentin erosive wear can be harmful. [ABSTRACT FROM AUTHOR]

The aim of this research was to evaluate the abrasive dentin wear that can be induced by three commercial whitening toothpastes following a tooth-brushing simulation (TBS) corresponding to a three-month period. Sixty human canines were selected, and the roots were separated from the crowns. Then the roots were randomly divided into six groups (n = 10) and were submitted to TBS using the following slurries: Group 1—deionized water (RDA = 5); Group 2—ISO dentifrice slurry (RDA = 100); Group 3—a regular toothpaste (RDA = 70); Group 4—a charcoal-containing whitening toothpaste; Group 5—a whitening toothpaste containing blue covasorb and hydrated silica; and Group 6—a whitening toothpaste containing microsilica. Following TBS, surface loss and surface roughness changes were evaluated using confocal microscopy. Additionally, surface morphology and mineral content changes were observed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The deionized water group presented the lowest surface loss (p < 0.05), while the charcoal-containing toothpaste presented the highest surface loss, followed by ISO dentifrice slurry (p < 0.001). Blue-covasorb-containing and regular toothpastes did not present statistically significant differences (p = 0.245), and neither didmicrosilica-containing toothpaste or ISO dentifrice slurry (p = 0.112). The surface height parameters and surface morphology changes of the experimental groups followed the surface loss patterns, while no differences were detected in mineral content after TBS.Although the charcoal-containing toothpaste exhibited the highest abrasive wear to dentin, according to ISO 11609, all the tested toothpastes exhibited appropriate abrasive behavior towards dentin.

• Studied hybrid gyroscope resonator damping mechanisms with imperfection sensitivity. • Realized thin film coated high precision resonator with few millions quality factor. • Limiting damping mechanisms are identified at each stage from design to realization. The performance of Hemispherical Resonator Gyroscopes (HRG) is decided by the mechanical resonator's Quality factor (Q factor). The Q factor is a measure of energy dissipation. A Q factor of few millions is needed to realize fine resolution millimeter size of the HRG for future interplanetary satellite missions. The objective is to carry out a detailed study of thermoelastic damping (TED), anchor loss, surface loss, material internal friction and fluid damping. A hybrid resonator is designed with very low TED. One of the major contributions of the present work is the study of the effect of thin film coating and different coating configurations on TED. Extensive simulations have been carried out on the effect of different fabrication deviations on anchor loss. A unique sensitivity study of mode interactions and mass unbalance pattern on frequency split and anchor loss mismatch is also done. Based on this, dimensional and geometric tolerances are derived for precision fabrication and the precision hybrid configuration resonator is realized. Surface loss and material internal friction are estimated. Also, surface characterisation has been done using nanoindentation techniques. Q factor of few millions is obtained in a fabricated precision resonator with thin film coating. Based on the estimation of different damping mechanisms and measurements, the limiting mechanisms are identified at each stage from the design to the realization. The Q factor of an uncoated resonator is limited by the surface loss while that of a coated resonator is limited by the coating induced additional TED, the coating material internal friction and the surface loss. [ABSTRACT FROM AUTHOR]

Objectives: The present study aimed to synthesize toothpastes containing Beta- TriCalcium Phosphate (β-TCP) nanoparticles, functionalized with fluoride and tin, and test their ability to reduce erosive tooth wear (ETW)., Methods: Toothpastes were synthesized with the following active ingredients: 1100 ppm of fluoride (as sodium fluoride, F - ), 3500 ppm of tin (as stannous chloride, Sn 2+ ), and 800 ppm of β-TCP (Sizes a - 20 nm; and b - 100 nm). Enamel specimens were randomly assigned into the following groups (n = 10): 1. Commercial toothpaste; 2. Placebo; 3 F - ; 4. F - + β-TCP a ; 5. F - + β-TCP b ; 6. F - + Sn 2+ ; 7. F - + Sn 2+ + β-TCP a and 8. F - + Sn 2+ + β-TCP b . Specimens were subjected to erosion-abrasion cycling. Surface loss (in µm) was measured by optical profilometry. Toothpastes pH and available F - were also assessed., Results: Brushing with placebo toothpaste resulted in higher surface loss than brushing with F - (p = 0.005) and F - + β-TCP b (p = 0.007); however, there was no difference between F - and F - + β-TCP b (p = 1.00). Commercial toothpaste showed no difference from Placebo (p = 0.279). The groups F - , F - + β-TCP a , F - + β-TCP b , F - + Sn 2+ , F - + Sn 2+ + β-TCP a and F - + Sn 2+ + β-TCP b were not different from the commercial toothpaste (p > 0.05). Overall, the addition of β-TCP reduced the amount of available fluoride in the experimental toothpastes. The pH of toothpastes ranged from 4.97 to 6.49., Conclusions: Although toothpaste containing β-TCP nanoparticles protected enamel against dental erosion-abrasion, this effect was not superior to the standard fluoride toothpaste (commercial). In addition, the functionalization of β-TCP nanoparticles with fluoride and tin did not enhance their protective effect., Clinical Significance: Although β-TCP nanoparticles have some potential to control Erosive Tooth Wear, their incorporation into an experimental toothpaste appears to have a protective effect that is similar to a commercial fluoride toothpaste., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objective: The aim of the present study was to evaluate the influence of multidirectional brushing on the surface roughness, morphology, and bonding interface of resin-repaired CAD-CAM ceramic and composite restorations., Materials and Methods: Twelve (N = 12) blocks (4 mm × 4 mm × 2 mm for parallel axis; 5 mm × 4 mm × 2 mm for perpendicular axis) of lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar AG) and CAD-CAM resin composite (Tetric CAD, Ivoclar AG) were obtained and repaired with direct resin composite (Clearfil AP-X, Kuraray). An abrasive slurry was prepared and the brushing was performed according to each restorative material and axis of brushing (n = 6; perpendicular to repair interface and parallel to repair interface) during 3,650 cycles (240 strokes per minute) to simulate 3 years of brushing. The surface roughness (Ra) and the profile variation for each material (restoration and direct repair resin composite) were measured at the baseline condition and after brushing, and the mean roughness and presence of steps at the repair interface were evaluated through factorial analysis of Variance (ANOVA). Scanning Electron Microscopy (SEM) images were taken to evaluate the surface topography of the repaired materials after brushing., Results: The mean roughness of the repaired CAD-CAM restorations was affected by the brushing (P < .05), mainly when evaluating the repair material and the interface (P < .05), while the restorative CAD-CAM materials presented more stable values. The profile evaluation showed higher steps at the interface when repairing lithium disilicate than for CAD-CAM resin composite., Conclusion: Repaired CAD-CAM restorations were susceptible to wear after brushing simulation. The surface roughness of the direct resin composite was the most affected leading to step development at the interface, particularly in the repaired lithium disilicate samples. Cinical maintenance recalls and polishing protocols must be considered to enhance the longevity of such restorations., Competing Interests: Conflict of interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The critical functional part of any high performance resonance based sensor is a mechanical resonator. The performance is measured by resonator quality factor (Q-factor). Damping mechanisms such as thermoelastic damping (TED), anchor loss, surface loss, material internal friction, fluid damping and electronics damping are covered in this review with more focus on gyroscope resonators. Dissipations can be reduced by different means. Hence, the effects of various design to operational parameters on the Q-factor for different configurations, sizes and materials are reviewed in detail. Micro scale ring resonators can achieve a Q-factor of the order of hundreds of thousands. Macro scale hemispherical resonators are suitable for ultrahigh Q-factors. High temperature sensor operation is not preferred because of TED, while sub-zero operation is limited by material internal friction. Few orders of dissipation increase are seen with thin film metallic coating due to TED and coating material internal friction. High precision fabrication is mandatory to achieve the designed minimum anchor loss as it is highly sensitive to fabrication imperfections. Q-factor sensitivity to operating pressure is different for different resonator configurations. This review study helps to build a comprehensive mechanical resonator design, realization and operation strategy to achieve high sensor performance. A roadmap on future research requirements for developing compact mass producible CVG type sensors with ultrahigh Q-factor is also highlighted. [ABSTRACT FROM AUTHOR]

Aim: A combination of the proteins casein and mucin is known to modify the salivary pellicle and improve its protection of the underlying enamel from erosion. It is so far not known if this protection is confined solely to erosion, or if it also extends to abrasion, and this in vitro study aimed at investigating this question. Methods: A total of 72 human enamel specimens were prepared and randomly assigned to four groups: pellicle (P), casein/mucin (CM), pellicle + casein/mucin (PCM), and control (Ctrl). Each specimen underwent five cycles, each cycle consisting of a pellicle/treatment part, an erosion part (3 min in 1% citric acid, pH 3.6, 25°C, 70 rpm), and an abrasion part (50 toothbrush strokes within 25 s in toothpaste slurry with a 200-g load). The pellicle/treatment part consisted of 2 h of incubation in whole human saliva for group P, 2 h of incubation (25°C, 70 rpm) in a protein mixture of 1% casein and 0.27% mucin for group CM, and 2 h of incubation in saliva followed by 2 h of incubation in the protein mixture for group PCM. The fourth group (Ctrl) served as the control and was kept in a humid chamber without saliva or protein treatment. The enamel surfaces were scanned with an optical profilometer initially and after the final cycle, and surface loss was analyzed. Furthermore, the surface microhardness (SMH) was measured initially, after each pellicle/treatment part and each erosion cycle, and after the final abrasion cycle. The results were analyzed with Kruskal-Wallis and Wilcoxon tests with Bonferroni corrections. Results: The different treatments did not show differences in surface loss and therefore did not protect enamel from surface loss by abrasion. Nonetheless, we observed differences in the SMH values, namely the Ctrl group being significantly softer than the experimental groups. Conclusion: The observed differences in SMH suggest that a different abrasion protocol could lead to differences in surface loss, and further investigation of whether and under which conditions pellicle modification leads to increased resistance to abrasion remains worthwhile. [ABSTRACT FROM AUTHOR]

Air-abrasion pre-treatment with bioglass 45S5 against enamel erosive wear was investigated. Beneficial results regarding surface loss of enamel after erosion/abrasion challenge were reported. The treatment did not provide better behavior compared to SnF 2 gel treatment. Clinical studie s are needed to confirm the significance of this in-office treatment. The aim of this in vitro study was to evaluate the effect of air-abrasion surface pre-treatment with bioactive glass (BAG) 45S5 on enamel surface loss after erosion/abrasion challenge. Twenty-four sound bovine incisors were used for this study. Four experimental groups (n = 12) were assigned as follows: Group 1 was the negative control group, Group 2 specimens were treated with a SnF 2 gel (positive control group), Group 3 specimens were air-abraded with BAG 45S5 (ProSylc) and Group 4 received both treatments. The specimens were submitted to erosion/abrasion challenge using a common soft drink. Enamel surface loss was evaluated using an optical profilometer. Additionally, surface roughness (VSI method) and surface microhardness (Vickers method) changes were evaluated, as well as SEM and EDS analyses were performed on enamel surface. The data were statistically analyzed using one-way ANOVA and Tukey's post-hoc test at a level of significance a = 0.05. Surface pre-treatment with BAG 45S5 reduced surface loss in comparison with negative control group (p < 0.001), which exhibited the highest surface loss of the experimental groups (p < 0.05). The positive control group (SnF 2 treatment) and Group 4 specimens, which received both air-abrasion pre-treatment and SnF 2 treatment, presented the lowest surface loss (p < 0.05), but did not show significant differences to each other (p = 0.65). Air-abrasion pre-treatment with BAG 45S5 may be beneficial as an in-office preventive method for the limitation of enamel erosive wear induced by excessive consumption of soft drinks. The clinical significance of the results regarding this preventive method should be confirmed by clinical studies. [ABSTRACT FROM AUTHOR]

The purpose of this in vitro study was to evaluate the effect of a clinical preventive treatment using Er,Cr:YSGG laser irradiation on bovine enamel susceptibility after erosive challenge. Twelve sound bovine incisors were used and twenty-four enamel specimens were prepared in total. Two experimental groups (n = 12) were assigned as follows: Group 1 was the control group and in Group 2, the enamel specimens were irradiated with an Er,Cr:YSGG (2780 nm) laser system for 20 s, with average output power of 0.25 W, pulse repetition rate at 20 Hz without water or air flow and the pulse duration was fixed at 140 μsec. The tip diameter was 600 μm, the tip to tissue distance was 1 mm, the speed of handpiece movement was 2 mm/s, the power density was 88.34 W/cm2, and the fluence was 31.25 J/cm2. The specimens were submitted to erosive challenge using a common soft drink. Surface microhardness changes, surface roughness changes, and surface loss were evaluated after erosive challenge. The data were statistically analyzed using one-way ANOVA and Tukey's post-hoc test at a level of significance a = 0.05. Er,Cr:YSGG laser-treated enamel exhibited significantly less decrease in surface microhardness and significant less surface loss compared to control enamel after the erosive challenge (p < 0.05). The experimental groups did not show significant differences in surface roughness increase after the erosive challenge (p > 0.05). Er,Cr:YSGG laser treatment may be promising for the limitation of enamel erosive tooth wear induced by excessive consumption of soft drinks. Clinical studies are needed to clarify whether this protective effect is clinically significant. [ABSTRACT FROM AUTHOR]

In the present work, the residual activity induced in 181Ta targets bombarded with 16O beam in the energy range ≈70-100 MeV have been measured. Stacked foil activation has been employed to measure the cross-sections of the several radioisotopes populated through different nuclear reaction across various energies. Yields of the radio-isotopic products such as 194,193,192Tl, 193,192Hg, 192,191,190Au have been obtained with the help of the characteristic γ-lines. Further, calibration curves are deduced by observing remnant activity induced across different depths in the target material. As a result an attempt has been made to employ thin layer activation technique with increased sensitivity for the study of surface wear. [ABSTRACT FROM AUTHOR]

Objective: Devising effective measures for the prevention of hydrochloric acid (HCl)-induced erosion is of great significance. This is even more important in dentine, in which products have limited diffusion. Therefore, agents that can bind to proteins forming an acid-resistant gel-like coat, such as sucralfate, may stand out as a promising alternative. This study investigated the protective effect of sucralfate suspensions against HCl-induced dental erosion. Materials and methods: In the first experiment, hydroxyapatite (HAp) crystals were pre-treated with a commercial sucralfate suspension (CoSS, pH 5.9), a stannous-containing sodium fluoride solution (NaF/SnCl2 pH 4.5), two prepared sucralfate suspensions (PrSS, pH 5.9 and 4.5), or deionized water (DI, control). HAp dissolution was measured using a pH-stat system. In a subsequent experiment, embedded/polished enamel and root dentine slabs were allocated into five groups to be treated with one of the tested substances prior to and during erosion-remineralization cycles (HCl-2 min + artificial saliva 60 min, two times per day, 5 days). Surface loss was assessed profilometrically. Data were analyzed by ANOVA and Tukey's tests. Results: HAp dissolution was as follows: NaF/SnCl2 < CoSS < PrSS/pH 4.5, while PrSS/pH 5.9 = DI and both did not differ from CoSS and PrSS/pH 4.5. In enamel, surface loss did not differ between CoSS and PrSS/pH 4.5, with both having lower surface loss than PrSS/pH 5.9 and DI and NaF/SnCl2 differing only from DI. In root dentine, surface loss was as follows: CoSS < PrSS/pH 5.9 < (NaF/SnCl2 = DI), while PrSS/pH 4.5 = CoSS = PrSS/pH 5.9. Conclusion: Sucralfate suspension provided anti-erosive protection to HCl-induced erosion. Clinical relevance: Sucralfate may protect teeth against erosion caused by gastric acid. [ABSTRACT FROM AUTHOR]

Investigating the surface loss mechanism of hemispherical resonators is essential to further improve the performance of hemispherical resonant gyroscopes. Although many studies have focused on the surface loss mechanism and surface treatment process of fused silica hemispherical resonators, the bulk fabrication of high-quality factor (Q factor) hemispherical resonators is still a significant factor limiting the widely applied hemispherical resonant gyroscopes. To address this practical need, this paper first analyzes the formation mechanism of surface defects and their effect on energy loss. Then, a cyclic chemical etching method using hydrofluoric acid as an etchant is proposed to significantly improve the Q factor of the hemispherical resonator by improving the surface morphology. Finally, a surface loss model was developed based on the experimental results to reveal the mechanism of the effect of surface morphology evolution on the change of the quality factor of the hemispherical resonator. The results show that the developed etching method can significantly improve surface quality with minimal damage to the substrate. The resonator's Q factor increases to a final value of about 2 × 107 after chemical etching, which is improved by about 20 times. The developed loss model can screen hemispherical resonators with different performances according to the change of the Q factor during the etching process. The etching technique and screening method developed in this paper is essential for bulk fabricating high-quality factor hemispherical resonators. [Display omitted] • The resonator's Q factor strongly depends on the surface topography. • The proposed etching method improves surface quality and significantly increases the Q factor. • The energy loss model elucidates the mechanism of surface morphology evolution on the Q factor. • The loss model is capable of screening different performance resonators based on the variation of the Q factor. [ABSTRACT FROM AUTHOR]

The relationship between surface loss and field flatness in extended interaction device (EID) has been studied. The field flatness can influence the surface loss in the circuit and hence the efficiency of the device without changing the operation mode. A W-band nine-slot extended interaction circuit operating in the 2πmode has been used in this article. As an oscillator, the nine-slot interaction circuit has different surface loss regions when the field flatness is different. In the study of EID, the operation point is mainly determined by the slow wave structure, but the field flatness should also be studied carefully for it influences the surface loss in the circuit and hence the efficiency of the device. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the susceptibility of cut and uncut enamel surfaces to an erosive challenge and to examine the resultant characteristics/morphological changes. Ten extracted human incisors were used for preparation of enamel samples, and samples were immersed in citric acid. After 3 (total 3 min) and 6 cycles (total 6 min) of erosive challenges, surface loss (SL) and morphological changes were measured using scanning microscopy and FIB-TEM. Ca release (CA) and surface hardness (SH) were measured using a calcium-sensitive electrode and hardness tester respectively. Mean values of all measurements were statistically analyzed by using a t-test. Uncut enamel samples had significantly lower SL and greater SH than cut enamel (p<0.01). Cut enamel samples after 3 cycles showed higher CA compared with those from uncut enamel samples (p<0.05). Cut enamel was shown to be more susceptible to acidic dissolution and deeper acid penetration than uncut enamel after erosive demineralization. [ABSTRACT FROM AUTHOR]

In this study, a composite metamaterial unit cell is introduced based on experimentally proven circular fishnet metamaterials (CF-MMs) and its stripped versions to implement an absorber for Ku band microwave regime. The offered MM absorber shows the perfect absorptivity (99.9%), the near perfect absorptivity (96.2%) and the standard absorptivity (58%) over narrow band frequencies 14.28, 14.77 and 15.2 GHz, respectively. We offered a method to create a composite metamaterial unit cell consisting of resonant type metamaterial sub-unit cells that are not suitable for absorber implementations in normal conditions. The physical mechanism behind multi-band resonances in the left-handed medium (LHM) regime is explained in detail by revealing the reverse behavior in the right-handed medium (RHM) regime keeping a single resonance feature, based on cancellation of impinging electric fields and preservation of circulating electric fields around the MM space. A detailed analysis is performed to explore and compare the power losses due to imperfect dielectric and non-ideal conductor. [ABSTRACT FROM AUTHOR]

In this paper, we investigate loss mechanisms in piezoelectric-on-silica bulk acoustic wave resonators, including those resulting from thermoelastic damping (TED), surface roughness, and supporting tethers. Alternate resonator designs, piezoelectric materials, and fabrication processes are demonstrated to empirically test these loss mechanisms. Quality factors (Qs) in the order of \sim 16 000 at a center frequency of 5 MHz have been consistently measured for aluminum nitride (AlN)-on-silica coupled-ring resonators. It is shown that neither TED nor surface losses are the dominant sources of loss for AlN-on-silica resonators in the megahertz regime. Instead, it is suggested that charge redistribution loss resulting from non-uniform strain across the piezoelectric layer is the dominant loss mechanism, with a charge redistribution {Q} of \sim 38$ 000 at 5 MHz for AlN-on-silica devices. When all loss mechanisms are considered, the total {Q} is estimated to be 25000, a value comparable to the measured results of the piezoelectric-on-silica resonators of this paper. [2015-0004] [ABSTRACT FROM AUTHOR]

Thermoelastic dissipation (TED) is a fundamental energy loss process, which bears concern in all microelectromechanical resonators. High aspect ratio ( \boldsymbol R/\boldsymbol h ) 3-D micro-hemispherical shell resonators ( $\mu $ HSRs) have exceptionally low stiffness and are sensitive to dissipation forces both internally and at their surfaces. TED in $\mu $ HSRs originating in the bulk of the shell and near its surfaces due to asperities (roughness) is investigated. Rayleigh’s inextensional solutions for the lowest frequency vibration modes of $\mu $ HSRs in the isothermal quasi-static limit result in zero contributions to energy loss from bulk TED since no volumetric strain is generated in this approximation. After relaxing Rayleigh’s inextensional assumption, perturbational undulations of the shell’s neutral surface are found to cause non-zero bulk TED. The resulting quasi-inextensional vibration modes force the shell into an approximately anti-biaxial strain state, which stretch surface asperities along one axis and compress them along the other, generating thermal flux around the base of each asperity. Closed-form approximate analytical models are developed from the geometrical and material dependencies to predict the quality factor associated with bulk and surface TED, enabling examination of these effects across scale. Fully-coupled thermoelastic finite element models verify the above results. Finally, experimental results from fabricated $\mu $ HSRs are compared with the developed models. [2013-0229] [ABSTRACT FROM AUTHOR]

SUMMARY In designing solid-pole synchronous machines, it is important to take into account the surface eddy-current losses in the field pole cores. In this study, a solid-iron ring specimen is adopted as an approximate model of solid-pole surfaces in order to conduct a fundamental study of the surface losses. The influence of the minor hysteresis loops on the losses under dc-biased magnetization is investigated. The losses in the ring under dc-biased magnetization are measured and analyzed by finite element analysis (FEA). The losses computed by the FEA considering minor loops are nearly the same as those measured. In contrast, the eddy-current losses computed by FEA without considering minor loops are considerably inaccurate because the incremental permeability is overestimated and the skin depth is underestimated. It is important to consider hysteresis for the accurate calculation of the surface eddy-current losses under dc-biased magnetization. [ABSTRACT FROM AUTHOR]