Acrylic Rods Research Articles

Osmotic energy harvesting using acrylic acid hydrogel PET membrane

In this study, we investigated the osmotic energy harvesting using a cation-selective membrane. The cation-selective membrane was synthesized by the incorporation of acrylic acid hydrogel in a porous support membrane. FTIR analysis and SEM images confirmed the presence of the acrylic acid hydrogel rods inside the porous support material. The exposure of the acrylic acid hydrogel PET (AP) membrane to a concentration gradient culminated in the generation of electric power. The AP membrane was evaluated in regard to the following parameters: EDiff, Io, Pmax and t+. The maximum power obtained with the membrane was 1.10 μW at the 40-fold concentration gradient (test area∽ 100 mm2). Increasing the concentration gradient increased the power output. However, a decrease in power output was observed after a certain value of the concentration gradient. An enhancement in power output was noted as the fraction of acrylic acid within the membrane was augmented. Additionally, the cation transference number also increased owing to a high charge density and a reduction in the mesh size. The AP membrane was also investigated in acidic and basic media. The time-dependent study revealed the superior chemical stability of the AP membrane.

Correlation between Dental Composite Filler Percentage and Strength, Modulus, Shrinkage Stress, Translucency, Depth of Cure and Radiopacity.

Filler content in dental composites is credited for affecting its physical and mechanical properties. This study evaluated the correlation between the filler percentage and strength, modulus, shrinkage stress, depth of cure, translucency and radiopacity of commercially available high- and low-viscosity dental composites. Filler weight percentage (wt%) was determined through the burned ash technique (800 °C for 15 min). Three-point bend flexural strength and modulus were measured according to ISO 4049 with 2 mm × 2 mm × 25 mm bars. Shrinkage stress was evaluated using a universal testing machine in which composite was polymerized through two transparent acrylic rods 2 mm apart. Shrinkage was measured from the maximum force following 500 s. The translucency parameter (TP) was measured as the difference in color (ΔE00) of 1 mm thick specimens against white and black tiles. The depth of cure was measured according to ISO 4049 in a cylindrical metal mold (4 mm diameter) with a 10 s cure. Radiopacity was measured by taking a digital X-ray (70 kVp for 0.32 s at 400 mm distance) of 1 mm thick specimens and comparing the radiopacity to an aluminum step wedge using image analysis software. The correlation between the filler wt% and properties was measured by Pearson's correlation coefficient using SPSS. There was a positive linear correlation between the filler wt% and modulus (r = 0.78, p < 0.01), flexural strength (r = 0.46, p < 0.01) and radiopacity (r = 0.36, p < 0.01) and negative correlation with translucency (r = -0.29, p < 0.01). Filler wt% best predicts the modulus and strength and, to a lesser extent, the radiopacity and translucency. All but two of the high- and low-viscosity composites from the same manufacturer had statistically equivalent strengths as each other; however, the high-viscosity materials almost always had a statistically higher modulus. For two of the flowable composites measured from the same manufacturer (3M and Dentsply), there was a lower shrinkage stress in the bulk-fill version of the material but not for the other two manufacturers (Ivoclar and Tokuyama). All flowable bulk-fill composites achieved a deeper depth of cure than the flowable composite from the same manufacturer other than Omnichroma Flow Bulk.

MinION Sequencing of Fungi in Sub-Saharan African Air and a Novel LAMP Assay for Rapid Detection of the Tropical Phytopathogenic Genus Lasiodiplodia.

To date, there have been no DNA-based metabarcoding studies into airborne fungi in tropical Sub-Saharan Africa. In this initial study, 10 air samples were collected onto Vaseline-coated acrylic rods mounted on drones flown at heights of 15-50 meters above ground for 10-15 min at three sites in Ghana. Purified DNA was extracted from air samples, the internal transcribed spacer (ITS) region was amplified using fungal-specific primers, and MinION third-generation amplicon sequencing was undertaken with downstream bioinformatics analyses utilizing GAIA cloud-based software (at genus taxonomic level). Principal coordinate analyses based on Bray-Curtis beta diversity dissimilarity values found no clear evidence for the structuring of fungal air communities, nor were there significant differences in alpha diversity, based on geographic location (east vs. central Ghana), underlying vegetation type (cocoa vs. non-cocoa), or height above ground level (15-23 m vs. 25-50 m), and despite the short flight times (10-15 min), ~90 operational taxonomic units (OTUs) were identified in each sample. In Ghanaian air, fungal assemblages were skewed at the phylum taxonomic level towards the ascomycetes (53.7%) as opposed to basidiomycetes (24.6%); at the class level, the Dothideomycetes were predominant (29.8%) followed by the Agaricomycetes (21.8%). The most common fungal genus in Ghanaian air was cosmopolitan and globally ubiquitous Cladosporium (9.9% of reads). Interestingly, many fungal genera containing economically important phytopathogens of tropical crops were also identified in Ghanaian air, including Corynespora, Fusarium, and Lasiodiplodia. Consequently, a novel loop-mediated isothermal amplification (LAMP) assay, based on translation elongation factor-1α sequences, was developed and tested for rapid, sensitive, and specific detection of the fungal phytopathogenic genus Lasiodiplodia. Potential applications for improved tropical disease management are considered.

Imaging elastic waves in solids: how to use laser feedback interferometry to visualize them.

The use of ultrasonic elastic waves is a well established technique for non-destructive testing of materials and structures, in particular to exploit the interaction of waves with structural features to detect and characterize defects. Optical methods offer the advantage of visualising the distribution of elastic waves in a non-contact manner without disturbing the elastic wave. In this work we propose a laser feedback interferometry (LFI) based system as a cost effective, non-contact, alternative to a well established laser Doppler vibrometer technique. We demonstrate the visualization of the elastic waves, using an example of an elastic wave propagating through a prismatic acrylic rod. We show that the ultra-compact and simple implementation of LFI enables accurate visualization of the elastic waves in solids, and opens the pathway to a range of new opportunities in ultrasonic non-destructive testing and evaluation.

Dosimetric Study to Estimate Deviations in Delivered Radiation Dose due to Occluded Air Spaces in Vaginal Vault Brachytherapy Applications.

To develop a dosimetric tool to estimate the dose delivered in the presence of air pockets with EBT3 film while simulating the conditions of vaginal vault brachytherapy (VVBT) with 3.0 diameter cylindrical applicator at a prescription dose distance of 5mm from the surface of it. Six acrylic plates (10 cm x 10 cm, 0.5 cm thick) with four different types of slots were designed and produced locally. They can hold a cylindrical vaginal brachytherapy applicator in the centre, air equivalent material from the applicator's surface [(sizes 4.5 mm (A), 3.0 mm (B), and 2.0 mm (C)], EBT3 film at the prescribed dose distance, and holder rods. Plates were layered together with acrylic rods and assembled in a holding box in a water phantom. Three treatment plans done in TPS with prescription doses of 2 Gy, 3 Gy, and 4 Gy at 5.0 mm with a treatment length of 6 cm, and were executed in Co-60-based HDR brachytherapy unit (M/s SagiNova, Germany) with & without the placement of air equivalent material, and the dose received at slot locations A, B, & C were noted. The mean percentage deviation of measured dose without and with presence of air pocket at A, B and C was 13.9%, 11.0% and 6.4% respectively for all dose prescriptions. As the air pocket size expanded radially from 2.0 mm to 4.5 mm, the increase in dosage ranged from 6.4% to 13.9% which was due to the fact that the film was held at dosage prescription distance and the lack of attenuation of photons radially through air pocket. The present study can be carried out with a 3D printed phantom that simulates VVBT application having air pockets of different dimensions at different locations and also can be analyzed with Monte Carlo simulations.

Imaging and range estimations of prompt X-rays using YAP(Ce) camera during particle-ion irradiation to phantoms with air cavities

Low-energy X-ray imaging of prompt secondary electron bremsstrahlung X-rays (prompt X-rays) emitted during particle-ion irradiation is a promising method for range estimation. However, measurements have so far been conducted mainly for uniform phantoms of water or an acrylic block. Prompt X-ray imaging for phantoms with air cavities has not yet been extensively measured or evaluated with realistic conditions. Consequently, we conducted imaging of prompt X-rays using a pinhole YAP(Ce) camera during irradiation by protons as well as carbon ions to non-uniform acrylic phantoms with small cavities and then evaluated the images and estimated the ranges from the measured prompt X-ray images. The non-uniform acrylic phantom used for imaging had a cylindrical cavity with a 20-mm or 10-mm diameter in the phantom. During irradiation by protons or carbon ions, imaging of one of the phantoms was conducted using the pinhole YAP(Ce) camera with an air cavity as well as filling the cavity with an acrylic rod. For the phantom with a 20-mm-diameter cavity, the prompt X-ray images measured for both protons and carbon ions showed the shape of the cavity in the images, and the ranges could be estimated from the images. For the phantom with a 10-mm-diameter hole, although the shape of the hole could not be clearly observed, the ranges could also be estimated from the images. Furthermore, Monte Carlo simulated prompt X-ray images with different spatial resolution of the X-ray camera showed similar images to the measured images. We confirmed that prompt X-ray imaging of phantoms with air cavities using the pinhole YAP(Ce) cameras was possible and that prompt X-ray imaging is a promising approach for estimating the ranges for both protons and carbon ions, even for phantoms with air cavities.

Luminescence imaging of non-uniform phantoms during irradiation of protons

Although luminescence imaging during irradiation of protons is a useful method for range and dose estimations, it has only been attempted for uniform phantoms. Since luminescence imaging inherently has high resolution, we will be able to measure the images with non-uniform phantoms. Therefore, we measured the luminescence images for a non-uniform structured acrylic block during irradiation of protons. Imaging was conducted using a cooled charge-coupled device (CCD) camera during the irradiation of 129-MeV protons to an acrylic block with a 10-mm diameter hole in which an acrylic rod, air, or a titanium rod was inserted. Under these three different conditions, we could obtain different luminescence images for protons. The luminescence images with the acrylic rod showed uniform Bragg peaks in the lateral direction. In the luminescence images with air, a part of the Bragg peak under the hole was elongated. In the luminescence images with the titanium rod, the part of the Bragg peak under the hole was shortened. The ranges estimated from the depth profiles of the measured images matched the simulated results within a 1-mm difference. We confirmed that the luminescence imaging of non-uniform phantoms was possible and that ranges could be estimated from the images. We conclude that luminescence imaging is promising not only for uniform phantoms but also non-uniform phantoms.

A Simplified Spring winder For Clinical Application

Introduction: The fabrication of coils using heavy gauge stainless steel wire for use in appliances such as the Churro Jumper can be a tedious task and can often result in spaced coils that lead to more flexibility than can be desired, leading to a decreased force application and hence overall lengthened treatment time. Using well placed, tightly adherent coils the force of which can be controlled by placement of the desired number of coils can help to mitigate this shortcoming. Technique: The spring winder described here is easy to fabricate using easily available stationary articles which can be repurposed to form an efficient winder that can coil springs with reduced effort as compared to that would have been required when using orthodontic pliers only. The stationary repurposed for this winder is the electric etching pen which provides a good framework for fabricating the winder. In addition, clear acrylic is used along with a syringe body to hold the winding components. The syringe is filled up with clear acrylic and winding rods are laid down within the acrylic which holds it firmly in place. In addition, the syringe body is embedded into the electric pen handle which allows for easy turning the winder so as to exert effective force while reducing operator effort and fatigue. This also allows for winding of heavy gauge orthodontic wire with little effort. Conclusion: A simplified spring winder can be best indicated for the fabrication of coils for fixed functional appliances like Churro Jumper.

Simulation of the parametrs of the acrylic and specular light pipe for transmitting light radiation of the LED matrix

In this article, we simulated the parametrs of an acrylic and specular light pipe to transmit radiation from the LED matrix. The results of the experiment can be estimated using the dependence of the light flux on the number of reflections in the specular light pipe. Evaluation was conducted in the software package “Mathcad”. The possibility of providing illumination from 6 to 30 lx using the system of transportation of artificial light of roads \\ streets \\ squares depends on the class of the object. The study of the transmission of light through a specular and acrylic light pipe has shown that under equal conditions of light transport (the same power, the same aperture, the equal length of the light pipe, the same diameter of the light pipe), the acrylic fiber has the advantage. Losses using acrylic light pipe of 2000 mm are 24% whereas using specular light pipe they are 45%. However, if there is no limitation in the diameter of the light pipe, then it is preferable to use a specular one. For example, at 150 mm the losses are no more than 13%, which is not achieved with an acrylic light pipe even with a diameter of 10 mm, since when the radiation aperture is kept, a reduction in diameter leads to an increase of the interaction of the radiation with the walls of the acrylic rod and increase of the optical path.

THE IMMERSION OF ACRYLIC RESIN WITH INJECTION MOULDING TECHNIQUE ON LOOSE DENTURES DIMENSIONAL CHANGE

Background: Acrylic resin is the most commonly used denture base material. One disadvantage is that it can absorb water that can cause changes in dimensions. Changes in the dimensions of acrylic resin are influenced by processing acrylic resin. At present injection molding techniques are known to be better than compression molding. Dimension changes due to water absorption occur in the first 7 days and interval intervals of up to 12 days. Purpose: this study was to determine whether immersion of acrylic resin with Injection molding techniques had an effect on changes in dimensions. Method: The study was conducted on acrylic resin test rods with a size of 25 mm x 25 mm x 5 mm. by using injection molding techniques. Acrylic resins are immersed in water for 24 hours, 48 hours and 12 days. Changes in dimensions are measured using a caliper with an accuracy of 0.01 mm. Statistical analysis was performed using the normality test, homogeneity test, and ANOVA test. Results: this study found that there was no change in dimensions of acrylic resin with water-immersed injection molding techniques 24 hours, 48 hours and 12 days. Conclusion: That immersion of acrylic resin in water at 24 hours, 48 hours, and 12 days with injection molding techniques did not affect changes in dimensions.

Electrochemical Investigation of Oxygen Reduction Reaction on Type 316L Stainless Steel in NaCl Solutions in a Confined Space

Steel plate joints are commonly produced in the manufacturing process of steel structures such as automobiles and bridges. The steel plate joints suffer from aqueous corrosion in atmospheric environments. Especially, severe corrosion is often observed in the confined spaces between the steel plates because aqueous electrolytic solutions can be kept in the spaces. In this case, corrosion reaction rate of the steels in the confined space is basically controlled by the reduction reaction rate of dissolved oxygen. Therefore, it is important to estimate oxygen reduction reaction rate in the confined spaces to predict corrosion deterioration of steel plate joints. In this study, electrochemical investigation of oxygen reduction reaction rate in a confined space was performed. The material used in this study was austenitic stainless steel type 316L bar with various diameters from 5 to 20 mm. The type 316L bar was cut into a small cylindrical piece and the piece was embedded in epoxy resin after being contacted with a lead wire. The surface of the embedded stainless steel sample was ground with SiC papers down to JIS200 grit and then cleaned ultrasonically in EtOH. Test solutions were aqueous NaCl of different concentrations from 0.05wt% to 5wt%. The solutions were prepared with Milli-Q water and reagent grade sodium chloride. For the electrochemical measurements, the sample was set horizontally in a plastic vessel and then an acrylic rod of 20 mm in diameter, which was used as a crevice former, was placed above the sample surface to make a confined space between the sample and the rod. The gap between the sample surface and the rod was changed from 20 um to 200 um by using a laser displacement meter. Electrochemical measurements were conducted by a conventional three electrode method with a platinum wire (Pt) and a Ag/AgCl in a saturated KCl (SSE) as a counter electrode (CE) and a reference electrode (RE), respectively. Cathodic polarization curves for the sample were measured with various gaps at a potential sweep rate of 0.5mV/s. Cathodic polarization behavior for the sample measured in the confined spaces was similar as that measured in a bulk solution; a limiting current region due to oxygen reduction reaction was observed on the samples of various diameters in a confined space. It was confirmed that the limiting current density decreased with decreasing in the gap. This is attributed to be the difference in the oxygen diffusion rate on the sample in the confined space.

Monte Carlo simulations of different CT X-ray energy spectra within CTDI phantom and the influence of its changes on radiochromic film measurements

PurposeIn this work we use Monte Carlo simulations to investigate change in Computed tomography (CT) X-ray energy spectra between exposures in air and within CT dose index (CTDI) phantom. While the results of these simulations will be relevant when measuring CTDI with any dosimeter, we apply the appropriate beam quality change correction for CTDI measurements using XR-QA2 model GafChromic™ film. MethodsDose profiles were measured with film strips, sandwiched between acrylic rods cut in half, placed within CTDI phantoms and scanned before and after irradiation with document scanner in reflective mode. Reference dosimetry system was calibrated in terms of air kerma in air, which was converted into absorbed dose using ratio of mass-energy absorption coefficients water-to-air for a given beam quality, following the AAPM TG-61 protocol. ResultsBeam qualities for all film positions within CTDI phantom show beam softening for HVLs above 6 mm Al and beam hardening for HVLs bellow 6 mm Al. Calculated CTDI values using HVL in air for all CTDI positions, and those calculated using the appropriate calibration curves based on beam quality correction show for Head CTDI phantom differences ranging from 0.3% to 2.1% and for Body CTDI phantom from 2.5% to 5.7%. ConclusionsWe describe method for CTDI measurements using radiochromic film dosimetry protocol corrected by the beam quality change within the phantom. Our results show differences in CTDI measurements of up to 5.7% when compared to using film calibration curves for beam quality in air.

Blue laser diode-pumped Ce:YAG phosphor-coated cylindrical rod-based extended white light source with uniform illumination

We report the development of an extended white light source with uniform illumination using a cylindrical rod coated with Ce-doped YAG phosphor and excited by a blue diode laser. A long cylindrical rod made of transparent acrylic was first ground in order to diffuse laser light uniformly throughout the rod. Ce:YAG phosphor was then coated on the cylindrical rod and a blue color laser beam of 1 W power pumped into it. The laser beam propagates through the entire length of the rod via total internal reflection. This is possible because the laser light is highly directional and coherent with high brightness. To achieve a uniform scattering distribution of blue laser light throughout the length of the cylindrical rod, variations in grinding as well as making a hollow core inside the tube are reported. While propagating through the rod, the blue photons are also scattered out due to the rough scattering surface of the acrylic rod. Some of the blue photons are absorbed by yellow phosphor thus generating yellow color photons and the remaining blue photons are mixed with the yellow light generating white light. Such an extended light source acts as a conventional tubelight of 30 cm length. Due to this extended light source, the illumination is uniform and produces no glare as compared to high brightness laser-based point sources as well as LED-based white light sources. Since the phosphor is coated on the outside of the acrylic rod and laser power is distributed uniformly, the burning of phosphor is completely avoided. The light source was characterized by measuring Commission International de l’Eclairage coordinates and correlated color temperature. This kind of light source is highly useful for general purpose illumination.

EFFICIENCY OF WAX REMOVAL

Objectives: To Determine the efficiency of wax removal from denture baseresin using hot water at a range of temperatures with added detergentand to Study the effectsof mechanically modified surfaces of denture base resin on the efficiency of dewaxing usingthe above techniques. Settings: Eastman Dental Institute University Of London UK. Period:Jan 2007 to June 2007. Material and Methods: In this study cast acrylic rods 13 mm longand 6 mm in diameter were used. Three different surfaces were prepared for each rod,described as Polished, Abraded &amp; Grooved. Nine experimental groups, each consisting of tenspecimens were mechanically modified were contaminated with modeling wax, and then thosein each group were subjected to agitation in hot water with detergent at different range oftemperatures. The surfaces were then examined for traces of wax using Raman spectroscopy.Results: The spectrum for each specimen demonstrated peaks at different wavelengths andvarying intensities, the spectra demonstrated traces of wax on abraded surfaces showedleast wax when dewaxed at 100°C as compared abraded surfaces dewaxed at 65°C and 85°C temperatures respectively. Conclusion: The rough surfaces (abraded or grooved) showedmore wax retention as compared to polished surfaces. These surfaces are usually prepared bythe dental technician in a belief that modifying the ridge-lap area of the teeth will increase thebond strength between the teeth and the denture base. Residual wax can still remain on thetooth surface even after dewaxing it at 100˚C with detergent added to the water.

Comparing the Effects of Project-based Learning by Making Rubber Band Cars in a Regular Subject and an Extracurricular Activity

In a regular-curriculum for freshmen in the Department of Mechanical Engineering at Toyo University, we have provided a subject to design and build rubber-band cars since 2013. In this subject, students make rubber-band cars out of paperboards, acrylic rods, and rubber bands, so that they experience the basic development process from the beginning. Furthermore, the accuracy of their making processes can be evaluated by running the rubber band cars. From the results of a questionnaire, this project-based learning for freshman seemed to provide the motivation to learn technical classes. In order to maintain and improve the students’ motivation, we also started an extracurricular activity for creating a rubber-band car on which people can ride. In this paper, we introduce the PBL in regular subjects and the extracurricular activity and compare the effects and problems of them.

Effect of Composite Polymerization Stress and Placement Technique on Dentin Micropermeability of Class I Restorations.

To investigate the effect of polymerization stress and insertion technique on dentin micropermeability of composites placed under pulpal pressure. One high-viscosity conventional (HC; Filtek Supreme Ultra; 3M Oral), one low-viscosity conventional (LC; Filtek Supreme Ultra Flowable; 3M Oral), one high-viscosity bulk fill (HBF; Filtek Bulk Fill Restorative; 3M Oral), and one low-viscosity bulk fill (LBF; Filtek Bulk Fill Flowable; 3M Oral) composite were evaluated. Polymerization stress was measured with materials bonded to acrylic rods in a universal testing machine (n = 5). Class I preparations were made in extracted molars, in which tooth roots were removed and the pulpal chambers cleaned. Preparations were coupled to a hydraulic device to simulate pulpal pressure during composite placement (n = 5). Conventional composites were placed in two horizontal increments, while bulk fill materials were placed in one, single increment. Fluid flow rate (µl/min) and dentin micropermeability (%) were monitored. The restoration interface was observed under confocal laser scanning microscopy. LC and LBF presented statistically significant higher polymerization stress than HC and HBF. Fluid flow rate and dentin micropermeability did not differ among the groups. However, different patterns of fluid infiltration and interface integrity were observed. HC and HBF presented well-sealed surrounding margins with small gaps along the pulpal wall, while HBF demonstrated more cracks in the adhesive layer. LC and LBF restorations had larger gaps along all bonded interfaces. No difference in polymerization stress was found when conventional and bulk fill composites with similar viscosities were compared. Neither polymerization stress or placement technique demonstrated a significant effect on dentin micropermeability. The incremental placement technique using a conventional, high-viscosity composite exhibited qualitatively better marginal integrity.

Peep Shows on Display: Mounting Paper Theatres for Exhibitions

Abstract In the eighteenth century, paper theatres were presented in special boxes on fairs. This technical note describes three ways to present these small decorative art objects in exhibitions: mounting the paper theatres in a box of museum board, between acrylic glass rods or in a frame.

Study on the non-contact trapping of a small object using a pipe radiating travelling waves and a reflective rod—The effect of the shape of reflector surface on the trapping state

Flexural damped travelling waves can be excited in a lossy transmission pipe. The waves generate travelling acoustic flow in the inside of pipe and near the pipe end and the acoustic flow serves as travelling acoustic waves. It has been confirmed that a non-contact transportation of a small object can be performed in the pipe, and additionally, a small object can be trapped at a nodal point of the standing wave formed by placing a reflector rod near the pipe end. In the experiment, a polycarbonate pipe (Outer dia.:13 mm, Inner dia.:9 mm, Length:160 mm) for the lossy ultrasonic transmission pipe that a piezo-ceramic annular plate vibrating in the first radial vibration mode is adhered at the pipe end was tried and the study on the effect of the shape of reflector surface on the trapping state is considered. The reflector is made of an acrylic rod (Dia.:13 mm) and the reflective surface is formed in to the conical shape. It was confirmed that the conical shape to be adapted for the trapping exists. To improve in the trapping force of the device, we considered the pipe attaching a reflective ring at the pipe end. The apparatus and distinctive characteristics are shown.

SU‐F‐T‐75: Dosimetry Considerations in the Use of Hanging‐Eye Block for Lesions of the Conjunctiva

Purpose:Superficial lesions in the conjunctiva are frequently treated with en face electrons, using a hanging block to spare dose to the lens of the eye. Dose to the tumor and lens depend on the design and setup of the block and supporting apparatus. We performed in phantom measurements in order to characterize the dose sparing effects of the block as well as the under‐dosing effect under the supporting apparatus for 6 MeV treatment.Methods:The commercial hanging block studied uses a 1.2 cm diameter tungsten cylinder supported by a 3 mm diameter acrylic rod. Point dose measurements under the hanging block, under an unblocked part of the field, and under the acrylic rod were performed using MOSFET detectors. In addition, EBT3 film was used for both PDD and profile measurements at a depth in phantom of 3 mm for both 105 and 103 cm SSD.Results:MOSFET measurements reported a dose reduction of 95% under the tungsten block when using an SSD of 103 cm, and 86% when using an SSD of 105 cm at a depth in phantom of 3 mm. Film measurements showed that the area under the acrylic rod may be under‐dosed by as much as 30% when using 103 SSD. MOSFET measurements confirmed that when using an SSD of 103 cm, the area under the acrylic rod is under‐dosed by up to 30% at 3mm depth, compared to the unblocked part of the field.Conclusion:The effectiveness of the commercial hanging block apparatus depends on setup, with 95% lens sparing possible with an SSD of 103 cm. This short SSD is necessary for sharp penumbra. At this SSD, substantial under‐dosing under the acrylic support rod is possible. This must be mitigated with either feathering, or using an alternative method of support for the tungsten block.

PENGARUH WAKTU PENGADUKAN TERHADAP WAKTU GELASI BAHAN CETAK ALGINAT

Alginate is one of many dental materials that used for the impressing materials. Mixing time is one of factorsthat affected the setting time. The aim of this study was to determine the effect of mixing time at 30 seconds, 35seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds and 60 seconds on setting time of alginate. This studyused experimental method. The samples that used were 42 samples and divided into 7 groups of mixing time,that were 30 seconds (control), 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, and 60 seconds.Setting time was tested with acrylic test rod based on ADA specification no.18. The alginate powder was mixedwith water (10 gr : 23 ml ratio), then put in the mould. Acrylic test rod was placed in contact with the surface ofalginate dough. The setting time was measured from the starting of the mix to the time when alginate does notadhere to the end of the rod. Result of this study showed that the average of setting time of alginate which mixedfor 30 seconds (control), 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, and 60 seconds was120.17 ± 3.312 seconds, 119.00 ± 1.265 seconds, 118.17 ± 1.472 seconds, 114.83 ± 3.896 seconds, 112.00 ±1.673 seconds, 109.17 ± 0.983 seconds, and 105.33 ± 4.082 seconds respectively.&#x0D; One Way Anova test shows significant difference among all experimental group with p=0.000. The change of setting time alginate show significant difference with control group when it mixed for 45 seconds, 50 seconds, 55seconds, and 60 seconds.Keywords: alginate, mixing time, setting time