Acrylic Ring Research Articles

An air-triggered contact-separation rotating triboelectric nanogenerator based on rotation-vibration-pressure conversion

Energy harvesting using triboelectric nanogenerators (TENGs) has demonstrated great potential in powering sensor network nodes and become a promising alternative for battery-free portable and wireless electronics. Unlike most existing rotational sliding-mode TENGs, an air-triggered contact-separation rotating triboelectric nanogenerator (AT-TENG) based on rotation-vibration-pressure conversion is proposed to reduce the violent collision of triboelectric materials and enhance the durability in this paper. The distinguishing feature of the AT-TENG was indirectly-excited contact separation mode along with the air-film interaction, where the rotational motion was converted into an elastic sheet vibration via the magnetic coupling and then the periodic contact or separation between the FEP film and aluminum plate was induced by the alternating air pressure. The feasibility of the presented AT-TENG was verified by theoretical analysis, fabrication and experiments. The results indicated that the distance of PVC to aluminum, radius ratio of the FEP to PVC, chamber volume (denoted by the acrylic ring height), magnet coefficient and rotational speed brought a significant effect on the output behaviors of the AT-TENG. There was an optimal PVC-aluminum distance of 0.1 mm as well as the maximum output voltage increased firstly and then decreased with the enhancement of radius ratio. Also, the output voltage was roughly enhanced with the increasing ring height except a maximum value occurred at h = 3.6 mm and demonstrated a reducing trend as the magnet coefficients was increased. In addition, the AT-TENG could achieve a maximum voltage of 367 V, maximum average power of 128.7 μW, and highest charging electricity of 14.45 mJ in the experiments. Besides, a parallel 200 LEDs could be efficiently powered by the AT-TENG. Furthermore, the AT-TENG demonstrated a long-term durability and stability through the 106444-excitation testing. It is expected that this work can offer a useful reference for further improvements of the rotational TENGs.

Comparison of the Shear Bond Strength of Compomer Bonding on Different Enamel Surface Preparations

Objectives: To compare the effects of etching time and bonding agent application on the shear bond strength of compomer bonding in orthodontic bite raising. Methods: Seventy-five sectioned crown of maxillary premolar teeth were embedded in acrylic rings. The samples were divided into 5 groups according to enamel surface preparation before applying Ultra Band-Lok® (Reliance Orthodontic Products). Group 1: without surface preparation, Group 2: etched with 37% phosphoric acid (Kerr Gel Etchant, Kerr®) for 15 seconds, Group 3: etched with 37% phosphoric acid for 15 seconds, then apply bonding (OptiBond™ FL), Group 4: etched with 37% phosphoric acid for 30 seconds and Group 5: etched with 37% phosphoric acid for 30 seconds, then apply bonding. All samples were put through the thermocycling procedure and then shear bond strength was tested using the Universal Testing Machine. The mean and standard deviation of shear bond strength were statistically analyzed with two-way ANOVA and the enamel surface was observed by scanning electron microscope at 10,000x magnifications. Result: In Group 1, all Ultra Band-Lok® dislodged from the enamel surface during the thermocycling process. Consequently, shear bond strength testing could not be conducted for Group 1. The mean shear bond strength of Groups 2-5 were 19.80±7.06, 18.97±4.60, 18.04±5.09 and 16.80±5.47 MPa respectively. The mean shear bond strength of each group was not statistically significant difference (p=0.887). Conclusions: Varying enamel etching times (15 and 30 seconds) did not affect the compomer shear bond strength. Furthermore, the application of a bonding agent during tooth surface preparation did not significantly improve the bond strength between the compomer and the tooth surface.

Differential Calorimetric Sensor for Rapid H2O2 Quantification in Industrial Solutions

Introduction: A simple and inexpensive differential calorimetric sensor for rapid hydrogen peroxide (H2O2) quantification in industrial solutions was developed, characterized, and validated. An earlier method proposed by the authors, on which the developed sensor is based, was enhanced, allowing overcoming the issues with its practical application. Thus, the following goals were achieved: a response time of 195 s from sampling to the analytical result; the elimination of the influence of initial sample temperature on the precision of the result by a differential mode of measurement application; the elimination of the result precision degradation caused by the parasitic heat produced by the sample stirrer. A linear quantification range from 0.05 to 1.5 mol L-1 H2O2 with a limit of detection (LOD) of 0.035 mol L-1 H2O2 was reached by applying disposable catalyst holders with a lifetime of more than 50 quantifications. The catalyst surface area to sample volume ratio adjustment allows the sensor’s analytical characteristics adaptation to the industrial-technological process requirements. Background: Hydrogen peroxide is used as a reagent in the technological processes of several industrial branches, and the simple and fast monitoring of its concentration is critical for the maintenance of technological process stability. The common disadvantages of the existing sensors are the complex and long measuring procedures requiring sophisticated equipment and qualified personnel. Objective: This study’s objective is the development of a simple and inexpensive calorimetric sensor and measuring instrument for rapid H2O2 quantification in industrial solutions by nonqualified personnel. The sensor is based on the significant improvement of the reagent-less calorimetric method proposed by the authors earlier, allowing its simple and precise practical application. Drawbacks such as the result of precision degradation by the initial sample temperature and by parasitic heat production during the measurement were overcome by obtaining an economical, simple, rapid, and precise sensor. Methods: The temperature increase resulting from the heat generated during the catalytic H2O2 decomposition was recorded as a sensor response. A simple and inexpensive disposable acrylic ring covered by MnO2 serves as a specific catalyst for H2O2 decomposition. The sensor analytical characteristics were evaluated, and permanganate approach validation was conducted. Results: The developed sensor showed a linear response to H2O2 from 0.05 to 1.5 mol L-1 with a LOD of 0.035 mol L-1 and LOQ of 0.115 mol L-1 under optimized experimental conditions. The catalyst surface area to sample volume ratio adjustment allows the sensor’s analytical characteristics adaptation to the industrial process requirements. The results were validated using the permanganate approach application, obtaining recovery values of 98.7%–101.4%. Conclusion: A simple and economic calorimetric sensor for quick hydrogen peroxide quantification in industrial solutions was developed, characterized, and validated. Disposable catalyst-loaded rings were employed allowing 50 successive quantifications of 1 mol L-1 H2O2 with a relative error of 1.08%. The sensor construction enables easy catalyst replacement and adjustment of its analytical characteristics to the industrial technology requirements using catalyst rings with various catalyst surface areas.

Comparative evaluation of shear bond strength of various esthetic restorative materials to dentin: An in vitro study

To comparatively evaluate the shear bond strength of recent tooth-colored restorative materials to dentin. Flat dentinal surface were prepared from 60 caries free, extracted human permanent molars and were mounted in acrylic rings. These were randomly divided into four groups - Group A to Group D, according to the restorative material used i.e. Glass ionomer cement (Fuji IX), Giomer (Beautifil), an Ormocer-based composite (Admira) and Nano Ceramic restorative material (Ceram X). These restorative materials were applied on dentinal surface of all the specimens using nylon cylinders. The mounted samples were stored in distilled water for 24 hours and thermocycled. They were then subjected to shear bond strength test using universal testing machine. Data was analyzed using a one-way analysis of variance (ANOVA) and student's 't'-test. Ceram X (16.63 ± 0.94 MPa) and Admira (17.31 ± 0.95 MPa) were comparable in their bond strength values, but depicted significantly higher bond strength when compared to Beautifil (12.39 ± 1.05 MPa) and Fuji IX (7.76 ± 1.07 MPa). Nano-ceramic and ormocer-based restorative materials showed better bonding potential to dentin as compared to GIC and Giomer.

Imaging of Surface-Tension-Driven Convection Using Liquid Crystal Thermography

Surface-tension forces can drive fluid motion within thin liquid layers with a free surface. Spatial variations in the temperature of the free surface create surface tractions that drive cellular motions. The cells are most commonly hexagonal in shape and they scale on the thickness of the fluid layer. This investigation documents the formation of cells in the liquid film in the presence of a uniform-heat-flux lower boundary condition. Liquid crystal thermography was used to image the cells and measure the temperature distribution on the lower surface of the liquid layer. A 1.1 mm deep pool of silicone oil was supported on a 50 μm thick electrically heated metal foil. The oil was retained inside an independently heated acrylic ring mounted on the top surface of the foil and a dry-ice cooling plate served as the low-temperature sink above the free surface of the oil. Color images of hexagonal convection cells were captured using liquid crystal thermography and a digital image acquisition and processing system. The temperature distribution inside a typical cell was measured using thermographic image analysis. Experimental issues, such as the use of an independently heated retaining ring to control the height of the liquid film and the utility of a flux-based Marangoni number are discussed.

A New Technique With Sodium Hypochlorite to Increase Bracket Shear Bond Strength of Fluoride-releasing Resin-modified Glass Ionomer Cements: Comparing Shear Bond Strength of Two Adhesive Systems With Enamel Surface Deproteinization Before Etching

By eliminating the organic substances from the enamel surface before etching (deproteinization), orthodontic bond strength can theoretically be increased because the resulting etch-pattern is predominantly type 1 and 2, instead of type 3. Fluoride-releasing resin-modified glass ionomer cements (RMGIs) might then routinely be used to bond brackets, instead of composite resins. Reducing the incidence of white spot lesions, a major current iatrogenic effect of orthodontic treatment, is a worthy cause which might be achieved due to the fluoride-releasing properties of RMGIs. The objective of this study was to determine whether deproteinization of human dental enamel surfaces, with 5.25% sodium hypochlorite (NaOCl) before etching, increases orthodontic bracket shear bond strength (SBS) of 2 adhesive systems: a composite resin and a RMGI. Seventy-six extracted human premolars were cleaned, and randomly divided into 4 groups (2 experimental and 2 control), with 19 premolars in each group. In group 1 (experimental) and group 2 (control), brackets were bonded to the teeth using Transbond XT (3M Unitek Orthodontic Products, Monrovia, CA) and in group 3 (experimental) and group 4 (control), Fuji Ortho LC (GC America, Inc., Alsip, IL) was used. The buccal surfaces of the premolars in experimental groups 1 and 3 were deproteinized with 5.25% NaOCl for 1 minute followed by rinsing, drying, and acid etching for 30 seconds. Subsequently, the acid was rinsed off, the enamel was dried (and remoistened in the Fuji Ortho LC groups), and orthodontic brackets were bonded, either with primer and composite resin, or with RMGI. The same protocol was used in the 2 control groups (2 and 4), except that NaOCl was not used. The teeth were then stored in distilled water at room temperature for a maximum of 24 hours, thermo-cycled 500 times, between 5°C and 55°C, placed in a controlled Water Bath, at 37°C for 24 hours, mounted on acrylic rings, and debonded using a universal testing machine. The enamel surfaces were examined at 10× magnification to determine the amount of residual adhesive remaining on the tooth. An analysis of variance was used to determine whether there was a significant difference in SBSs between the 4 test groups, together with a post hoc test to determine possible significant differences among the pair of means; a χ 2 test was used to compare the adhesive remnant index (ARI) scores. There were no significant differences in the SBS ( P = 0.05) between the Transbond XT groups. There were significant differences in the SBS ( P = 0.05) between the Fuji Ortho LC groups. The mean SBS for Transbond XT with NaOCl was 9.41 ± 4.46 megapascals (MPa); for Transbond XT without NaOCl, 8.12 ± 3.10 MPa; for Fuji Ortho LC with NaOCl, 9.64 ± 5.01 MPa; and for Fuji Ortho LC without NaOCl, 5.71 ± 3.87 MPa. The comparisons of the adhesive remnant index scores between the 2 Transbond groups (χ 2 = 6.41) indicated that bracket failure mode was not significantly different ( P 2 = 24.08) indicated that bracket failure mode was significantly different ( P

In vitro wear of resin‐based materials—Simultaneous corrosive and abrasive wear

The aim of this study was to evaluate the wear of resin-based materials caused by the association of abrasive and corrosive processes. Twenty specimens were prepared for each material, cast in epoxy in acrylic rings, polished, and profiled with an MTS 3D Profiler. Antagonists were made from deciduous molars. Specimens were distributed into eight groups (n = 10), according to the material (Filtek Supreme, Point 4, Dyract AP, and Fuji II LC) and the type of slurry (neutral and acidic), and then cycled 100,000 times in the OHSU oral wear simulator. The specimens were cleaned and reprofiled. Volume loss and maximum depth were determined. ANOVA and Tukey's test were used for data analysis (p < 0.05). The area of the wear facet on the antagonist was also measured. Composites displayed less wear than the compomer and the resin-modified glass ionomer. Significant differences also were found for cusp wear, with a significant positive correlation shown between cusp and material wear. The acidic slurry significantly increased the wear of the materials compared to the neutral slurry. Exposure to acidic slurry accelerated the wear of resin-based materials.

Surgical Pearl: Surgical tape for dressing of epidermal grafts in lip vitiligo

tissue heating, thus avoiding unintended injury. For larger surgical defects, local, uniform pressure can be applied with the locked jaws of the hemostat parallel to the wound edge while holding the instrument at its base, which is at a safe distance from the wound (Fig 2). If bleeding is likely fed from a vessel with a known path, the pressure may be directed closer towards that vessel’s origin and at an even greater distance from the wound (eg, at the eyebrow to block the supra-orbital artery). In addition to improved safety, other advantages of this technique include the fact that it is nearly universally applicable, is easy to perform for even an untrained assistant, and does not require additional instruments on the surgical tray. An important limitation exists in that deeper layers must offer some resistance to the pressure. Various articles have described similar techniques of temporary hemostasis using pressure from firm devices; however, these either used specially-made instruments or were anatomically limited in their scope of application. In summary, this technique offers a fast and convenient method for temporary hemostasis that is safely and easily performed by assistants with little experience, and therefore may be especially helpful in a training environment. REFERENCES 1. Yen A, Braverman IM. Ultrastructure of the human dermal microcirculation: the horizontal plexus of the papillary dermis. J Invest Dermatol 1976;66:131-41. 2. Grabb WC. A concentration of 1:500,000 epinephrine in a local anesthetic solution is sufficient to provide excellent hemostasis. Plast Reconstr Surg 1979;63:834. 3. Rudolph H, Gartner J, Studtmann V. Skin lesions following the use of a tourniquet. Unfallchirurgie 1990;16:244-51. 4. Sawchuk WS, Friedman KJ, Manning T, Pinnell SR. Delayed healing in full thickness wounds treated with aluminum chloride solution. A histologic study with evaporimetry correlation. J Am Acad Dermatol 1986;15:982-9. 5. Armstrong RB, Nichols J, Pachance J. Punch biopsy wounds treated with Monsel’s solution or a collagen matrix. A comparison of healing. Arch Dermatol 1986;122:546-9. 6. Boyer JD,Maino KL, Zitelli JA. Surgical pearl: hemostasis assisted with two skin hooks. J Am Acad Dermatol 2002;47:938-9. 7. Fante RG, Fante RL. Perspective: the physical basis of surgical electrodissection. Ophthal Plast Reconstr Surg 2003;19:145-8. 8. Hafner J, Hohenleutner U. Surgical pearl: A flat plastic cylinder derived from a disposable syringe effectively achieves hemostasis in carbon dioxide laser surgery. J Am Acad Dermatol 2001;45:277-8. 9. Wheeland RG, Gilmore WA, Morgan RJ. Use of a nonconductive acrylic ring for control of bleeding during minor skin surgery. J Dermatol Surg Oncol 1983;9:18-9. 10. Sharquie KE, Al-Rawi JR. Sharquie’s metal ring in skin surgery. Dermatol Surg 2000;26:163-4. 11. Harahap M. Excision of small skin lesions on the scalp. In: Robins P, editor. Surgical gems in dermatology. Vol 1. New York: Journal Publishing Group; 1988. pp. 73-4. J AM ACAD DERMATOL SEPTEMBER 2005 498 Pearls

MEASUREMENT OF MEAN SKIN TEMPERATURE: ???COVERED??? VS.???UNCOVERED??? CONTACT THERMISTORS

1620 The purpose of this study was to compare the mean skin temperature(Tsk) obtained using “covered” vs. “uncovered” contact thermistors in a variety of environmental conditions. Ten male subjects walked on a treadmill at 4 mph for 30 min in three different environments: temperate (23 °C/50% rH), hot-humid (35 °C/80%), and hot-dry (42 °C/20%). Tsk was measured using three“uncovered” contact thermistors, and three “covered” thermistors. The “uncovered” probes were attached using acrylic rings that allowed the outer surface of the thermistors to have free exchange with the environment. The “covered” probes were affixed to the skin using foam patches and tape. The latter procedure is commonly used in many research and clinical laboratories. The “covered” probes resulted in a significantly (p<0.05) higher Tsk under all three environmental conditions. The largest difference occurred in the temperate condition with the “covered” Tsk being 1.3 °C higher than the “uncovered” Tsk. Furthermore,“covered” vs. “uncovered” forearm Tsk was measured in a variety of ambient air temperatures ranging from 12 °C to 43°C. The results showed that ▵ (“covered” minus“un-covered”) forearm Tsk was inversely correlated (r=-0.97) with ambient air temperature. These results suggest that covering a contact skin thermistor hinders heat loss and results in an artificially high Tsk. The results of this study will hopefully encourage the adoption of using “uncovered” contact skin thermistors in the future.

Comparison of mean skin temperature using `covered' versus `uncovered' contact thermistors

The purpose of this study was to compare the mean skin temperature obtained using `covered' versus `uncovered' contact thermistors in a variety of environmental conditions. Ten male subjects walked on a treadmill at 6.4 kph for 30 min in three different environments: thermoneutral , hot-humid , and hot-dry . was measured using three `uncovered' contact thermistors, and three `covered' thermistors. The `uncovered' probes were attached using acrylic rings that allowed the outer surface of the thermistors to have free exchange with the environment. The `covered' probes were affixed to the skin using foam patches and tape. The latter procedure is commonly used in many research and clinical laboratories. The `covered' probes resulted in a significantly (p < 0.05) higher under all three environmental conditions. The largest difference occurred in the thermoneutral condition with the `covered' being higher than the `uncovered' . These results suggest that covering a contact skin thermistor hinders heat loss and results in an artificially high . It is hoped that the results of this study will encourage the adoption of `uncovered' contact skin thermistors in the future. Keywords: mean skin temperature, forearm skin temperature, contact themistors

Effects of polymerization contraction in composite restorations.

Post-gel polymerization contraction of resin composite induces contraction stresses at the composite-tooth bond and in surrounding tooth structure. Strain gauges have been shown to be an effective method for measuring linear post-gel polymerization contraction of composites. A new model was developed in which the composite sample was bonded to and circumscribed by an acrylic ring. The model simulates a composite restoration surrounded by dentine. A strain gauge measured the deformation of the ring while a second strain gauge simultaneously recorded the dimensional change of the sample. Stresses placed on the acrylic ring as a result of polymerization contraction of the composite were calculated, based on the strains on the ring and the ring's material properties. Four composites (Heliomolar, Vivadent, Tonawanda, NY, USA; Herculite XR, Kerr Manufacturing Co., Romulus, MI, USA; P-50, 3M Co., St Paul, MN, USA; Silux Plus 3M Co.) were evaluated for polymerization contraction strain and stress on the surrounding acrylic ring during polymerization. At the end of the 60 s light application, Heliomolar demonstrated significantly lower post-gel contraction (0.12 per cent, P less than 0.05) when compared to the other materials. When the strain reached an equilibrium at the end of 14 min Heliomolar continued to demonstrate lower post-gel contraction, however this was not statistically significant at P less than 0.05. When the contraction stress on the surrounding acrylic ring was considered, P-50 rapidly developed and produced the largest stress values (1.7 MPa) at the end of the light application while Heliomolar produced the lowest stress values (0.3 MPa). These values, however, were not significantly different when evaluated statistically.(ABSTRACT TRUNCATED AT 250 WORDS)

Hygroscopic setting expansion of gypsum-bonded investment under restrictive stress in dental casting

The phenomenon of hygroscopic setting expansion of gypsum-bonded investment under restrictive stress for dental casting was studied. The analysing method for normal setting expansion proposed in previous studies was also applied to hygroscopic setting expansion under uniaxial stress and within an acrylic ring. Furthermore, hygroscopic setting expansion within a stainless steel ring with an asbestos liner was analysed under dental casting conditions in relation to the calculation method proposed by the authors.

A method for evaluation of brain tumor growth using implantable diffusion chambers

Major drawbacks associated with in vitro assays for sensitivity of brain tumors to specific chemotherapeutic drugs include uncertainty of end-point validity, the need for large tissue samples, and cost. Furthermore, these assays do not address the question of conversion of the drug to active moeities by metabolic pathways in the host or alteration of drug activity by binding to plasma protein. We propose to develop a technique for growth and quantitation of tumor cells in small-pore diffusion chambers that contain the tumor cells and protect them from the immune system of the immunologically unrelated host. These chambers, fabricated from acrylic rings and membranes of 0.22 μm pore size, are sterilized, filled with a precisely quantitated inoculum of tumor cells, and implanted in the peritoneal cavity of rats. Replication of the cells is determined by enzymatic digestion of the supporting matrix of the cells within the chamber and counting the single cell suspension with a hemocytometer or automated cell counter. Precise comparison can thus be made between different drugs regarding their effect on cell growth in the host. This assay can be performed with the basic equipment and personnel available in most cell culture laboratories and requires a small number of tumor cells. Mass production of the diffusion chambers may make the assay less costly and faster than assays that do not involve exposure of tumor to drug in a living host. In addition, the assay should permit screening of new chemotherapeutic agents against human tumors under physiologic conditions.