In electron therapy, lead cutout or low-melting alloy block is used for shaping the field. Material for shaping electron field affects the output factor as well as the collimation system. The authors measured the output factors of electron beams for shaped fields from Clinac-18 using ionization chamber of Farmer type on polystyrene phantom. They analyzed the incident energy, collimation system and size of shaped field. For shaped field the variation of output factor for the field (A/P) has appearance of a smooth curve for all energy and all applicator collimator combination. The output factors for open field deviate from the curves for shaped fields. An output factor for a given field can be calculated by equivalent field method such as A/P method, if a combination of applicator and collimator is fixed.
Alloys ; Polystyrenes

Several combinations of measuring devices and phantoms were studied to measure electron beams. Silicon PN junction diode was used to find the dependence of depth dose profile on field size on axis of electron beam Depths of 50, 80 and 90% doses increased with the field size for small fields. For some larger fields, they were nearly constant. The smallest of field sizes over which the parameters were constant was enlarged with increase of the energy of electron beams. Depth dose distributions on axis of electron beam of 10 x 10 cm2 field were studied with several combinations of measuring devices and phantoms. Cylindrical ion chamber could not be used for measurement of surface dose, and was not convenient for measurement of near surface region of 6 MeV electron. With some exceptions, parameters agreed well with those studied by different devices and phantoms. Surface dose in some energies showed 4% difference between maximum and minimum. For 18 MeV, depths of 80 and 90% doses were considerably shallower by film than by others. Parallel-plate ion chamber with polystyrene phamtom and silicon PN junction would be recommended for measurement of central axis depth dose of electron beams with considerably large field size. It is desirable not to use cylindrical ion chamber for the purpose of measurement of surface dose or near surface region for lower energy electron beam. It is questionable that film would be recommended for measurement of dose distribution of electron with high energy like as 18 MeV.
Axis, Cervical Vertebra ; Polystyrenes ; Silicones

BACKGROUND AND OBJECTIVES: Colonization of microorganisms on pollutants is the first indication of the potential ability of microbes to utilize plastic pollutants as a carbon source by sequential biodegradation into usable form for sustenance. The Philippines is considered the third highest country contributing to global mismanaged plastic waste. To locally manage and find a natural and innovative solution to this worldwide concern, this study aimed to evaluate the capacity of Xylaria sp. SDM (sterile dark mycelia) wild type, which was previously reported to colonize polyethylene plastic and mutant strains to colonize polystyrene, a plastic pollutant widely produced in the world. Assessment of the ability of local Xylaria sp. strains to grow, penetrate, and damage the surface and inner structures of polystyrene was investigated using scanning electron microscopy (SEM).

METHODOLOGY: Xylaria sp. strains were cultured in a pH 5.0 mineral medium with 0.5% glucose as carbon source and polystyrene as a co-carbon source, and stored at 25?C for 50 days. At the end of the incubation period, due to irremovable fungal strains on the surface of the polystyrene strips, samples of polystyrene from each strain were subjected to SEM.

RESULTS: On the 20th day of incubation, the presence of mucilaginous sheaths and fungal growth was observed on the surface of treated polystyrene strips. At the end of the 50-day incubation period, scanning electron microscopy (SEM) confirmed fungal growth and colonization, through the presence of mycelial mats and hyphae, of the wild type and mutant strains on the surface and inner structures of polystyrene except the control. Moreover, physical surface damage in the form of holes, cracks, and crevices on polystyrene demonstrated the active burrowing action of Xylaria sp. strains further supporting the potential of this fungus to damage polystyrene plastic.

CONCLUSION: Whereas fungal growth on a polymer surface is necessary but not sufficient to conclude the process of carbon assimilation as the final biodegradation step, the initial colonization of Xylaria sp. strains on polystyrene supports its ability to establish itself and physically damage the pollutant. Hence, this study extended the existing knowledge on the colonizing ability of Xylaria sp. on plastic making it a potential candidate organism to biodegrade plastic waste, which is one of the topmost environmental waste hazards in the world today.

No abstract available.
Herpes Simplex ; Herpes Zoster ; Humans ; Methylmethacrylates ; Polystyrenes

No abstract available.
Latex* ; Polystyrenes* ; Potassium Channels* ; Potassium* ; Vasospasm, Intracranial*

PURPOSE: The wedge filter is the most commonly used beam modifying device during radiation therapy. Recently dynamic wedge technique is available through the computer controlled asymmetric collimator, independent jaw. But dosimetric characteristics of dynamic wedge technique is not well know. Therefore we evluate dosimetric characteristics of dynamic wedge compared to conventional fixed wedge. MATERIALS AND METHODS: We evaluated dosimetric characteristics of dynamic wedge and fixed wedge by ion chamber, film dosimetry and TLD in phantoms such as water, polystyrene and average breast phantom. Six MV x-ray was used in 15X15 cm field with 15,30 and 45 degree wedge of dynamic/fixed wedge system. Dosimetric characteristics are interpreted by wellhofer Dosimetrie system WP700/WP700i and contralateral breast dose(CBD) with tangential technique was confirmed by TLD. RESULTS: 1) Percent depth dose through the dynamic wedge technique in tissue equivalent phantom was similar to open field irradiation and there was no beam hardening effect compared to fixed wedge technique. 2) Isodose line composing wedge angle of dynamic wedge is more straight than hard wedge. And dynamic wedge technique was able to make any wedge angle on any depth and field size. 3) The contralateral breast dose in primary breast irradiation was reduced by dynamic wedge technique compared to fixed wedge. When the dynamic wedge technique was applied, the scatter dose was similar to that of open field irradiation. CONCLUSION: The dynamic wedge technique was superior to fixed wedge technique in dosimetric characteristics and may be more useful in the future.
Breast ; Film Dosimetry ; Jaw ; Polystyrenes ; Water

As a benign adnexal tumor, steatocystoma usually occurs as an autosomal dominant condition known as steatocystoma multiplex. Steatocystoma simplex, the noninherited solitary counterpart of steatocystoma multiplex,was first described by Brownstein in 1982, and is exceedingly rare. We report a case of steatocystoma simplex in a 27-years-old female, who presented with an asymptomatic soft, oval shaped mass on the lower anterior neck. The lesion was completely excised and confirmed as steatocystoma simplex on histopathological examination.
Female ; Humans ; Methylmethacrylates ; Neck ; Polystyrenes ; Steatocystoma Multiplex

The purpose of this study was to evaluate the biocompatibility of polystyrene, titanium, and A-W ceramic focusing on the affinity of osteoblasts to the metals. Human osteoblasts were cultivated with each material (group I : polystyrene; group II :titanium; and group III:A-W ceramic) for seven days. Serial scanning electromicroscopic (SEM) examination and quantitative analysis of cellular protein synthesis were performed in each group of material. SEM examination showed that at the first day, the osteoblasts in group II and group III had longer and abundant cytoplasmic spindles than those in group 1. At the seventh day, the particulate networks (diameter 1-2 urn) were observed on the surfaces of osteoblasts in group I and group II but not in group III. In all groups, the amount of protein synthesis tended to increase with days of culture. Furthermore the actual amount was significantly larger in the orders of group III, group II, and group I (p<0.05, in all comparisons). This in vitro study suggests that when other factors are controlled, the superior affinity of human osteoblast to A-W ceramic might be attributable to the better biocompatibility than that of titanium and polystyrene.
Ceramics* ; Cytoplasm ; Glass* ; Humans* ; Metals ; Osteoblasts* ; Polystyrenes ; Titanium

PURPOSE: This study was performed to measure dose alteration at the air-tissue interface resulting from rebuild-up due to the loss of charged particle equilibrium in the tissues around the air-tissue interfaces. MATERIALS AND METHODS: The 6 and 10-MV photon beam in dual energy linear accelerator were used to measure the surface dose at the air-tissue interaface. The polystyrene phantom sized 25 X 25 X 5 cm3 and a water phantom sized 9 X 29 X 48 cm3 which incorporates a parallel-plate ionization chamber in the distal side of air gap were used in this study. The reatment field sizes were 5 X 5 cm2 , 10 X 102 , and 20 X 20 cm2 . Air cavity thickness was variable from 100 mm to 50 mm. The observed-expected ratio (OER) was defined as the ratio of dose measured at the distal junction, that is air-tissue interface, to the dose measured at the same point in a homogeneous phantom. RESULTS: In this experiment, the result of OER was close or slightly over than 1.0 for the large field size but much less (about 0.565) than 1.0 for the small field size in both photon energy. The factors to affect the dose distribution at the air-tissue interface were the filed size, the thickness of air cavity, and the photon energy. CONCLUSION: Thus, the radiation oncologist should take into account dose reduction at the air-tissue interface when planning the head and neck cancer, especially pharynx and laryngeal lesions, because the dose can be less nearly 29% than predicted value.
Head and Neck Neoplasms ; Particle Accelerators ; Pharynx ; Polystyrenes ; Water

No abstract available.
Encephalitis, Herpes Simplex ; Herpes Simplex ; Methylmethacrylates ; Neurosyphilis ; Polystyrenes