Evaluation of Air-Kerma and Absorbed Dose to Water for External Radiotherapy Beam Using Ionization Chamber

Radiotherapy is the most widely applied oncologic treatment modality utilizing ionizing radiation. A high degree of accuracy, reliability and reproducibility is required for a successful treatment outcome. Measurement using ionization chamber is a prerequisite for absorbed dose determination for external beam radiotherapy. Calibration coefficient is expressed in terms of air kerma and absorbed dose to water traceable to Secondary Standards Dosimetry Laboratory. The objective of this work was to evaluate the level of accuracy of ionization chamber used for clinical radiotherapy beam determination. Measurement and accuracy determination were carried out according to IAEA TRS 398 protocol. Clinical farmers type ionization chamber measurement and National Reference standard from Secondary Standards Dosimetry Laboratory were both exposed to cobalt-60 beam and measurement results compared under the same environmental conditions. The accuracy level between National Reference Standard and clinical radiotherapy standard was found to be −1.92% and −2.02% for air kerma and absorbed dose to water respectively. To minimize the effect of error and maximize therapeutic dose during treatment in order to achieve required clinical outcome, calibration factor was determined for air kerma (Nk) as 49.7 mGy/nC and absorbed dose to water ND, as 52.9 mGy/nC. The study established that radiotherapy beam measurement chain is prone to errors. Hence there is a need to independently verify the accuracy of radiation dose to ensure precision of dose delivery. The errors must be accounted for during clinical planning by factoring in calibration factor to minimize the systematic errors during treatment, and thereby providing enough room to achieve ±5% dose delivery to tumor target as recommended by ICRU.

Application of sustainable basil seed as an eco-friendly multifunctional additive for water-based drilling fluids

Basil seed,containing anionic heteropolysaccharides in its outer pericarp,swells as gelatinous hydrocolloid when soaked in water.In this study,basil seed powder(BSP)was used as a multifunctional additive for water-based drilling fluids.The chemical composition,water absorbency,rheological properties of aqueous suspension of BSP were tested.The effect of BSP on the rheological and filtration of bentonitebased drilling fluid before and after thermal aging was investigated.The inhibition characteristics were evaluated by linear swelling,shale cuttings dispersion and shale immersion test.Lubricity improvement by BSP was measured with extreme pressure lubricity test.The results revealed that incorporation of BSP into bentonite suspension improved rheological and filtration properties effectively after thermal aging of 120℃.BSP exhibited superior inhibitive capacity to xanthan and synergistic effect with KCl.BSP could reduce friction by forming hydration layer.The nanoscale three-dimensional network structures enable BSP to maintain high water retention and absorb strongly on bentonite and metal surface,contributing to enhanced rheology,filtration,inhibition and lubrication properties.The versatile characteristic of BSP,as well as biodegradation makes it a promising additive using in high performance water-based drilling fluid and a potential alternative to conventional synthetic polymers.

Evaluation of Dosimetric Impact of Uncertainty of Measurement in Estimating External Radiotherapy Dose

Cancer is a major societal public health and economic problem, responsible for one in every six deaths. Radiotherapy is the main technique of treatment for more than half of cancer patients. To achieve a successful outcome, the radiation dose must be delivered accurately and precisely to the tumor, within ± 5% accuracy. Smaller uncertainties are required for better treatment outcome. The objective of the study is to investigate the uncertainty of measurement of external radiotherapy beam using a standard ionization chamber under reference conditions. Clinical farmers type ionization chamber measurement was compared against the National Reference standard, by exposing it in a beam 60Co gamma source. The measurement set up was carried out according to IAEA TRS 498 protocol and uncertainty of measurement evaluated according to GUM TEDDOC-1585. Evaluation and analysis were done for the identified subjects of uncertainty contributors. The expanded uncertainty associated with 56 mGy/nC ND,W was found to be 0.9% corresponding to a confidence level of approximately 95% with a coverage factor of k = 2. The study established the impact of dosimetry uncertainty of measurement in estimating external radiotherapy dose. The investigation established that the largest contributor of uncertainty is the stability of the ionization chamber at 36%, followed by temperature at 22% and positioning of the chamber in the beam at 8%. The effect of pressure, electrometer, resolution, and reproducibility were found to be minimal to the overall uncertainty. The study indicate that there is no flawless measurement, as there are many prospective sources of variation. Measurement results have component of unreliability and should be regarded as best estimates of the true value. .

Preparation of Liquor Flavoring from Yellow Water Based on Water Absorbent Resin

[Objective] This study was conducted to extract the scarce natural liquor flavorings desired by many liquor factories from yellow water. [Method] Strong water absorbent resin was used to absorb moisture from the yellow water in order to concentrate it into dense yellow water at first, followed by azcotropic dis- tillation of the previously concentrated yellow water, and then, catalytic esterification was performed to the remaining liquid after the distillation. [ Results] The 7. 066 7 fractions of concentrated yellow water with 56.7% ethanol could be obtained after the treatment of 100 fractions of yellow water with strong water absorbent resin. Azeotrope of 0.432 8 fraction of natural acetaldehyde, 0. 269 4 fraction of ethyl formate and methyl alcohol, 0. 975 0 fraction of ethyl acetate and methyl alco- hol could be obtained after the azeotropic distillation per 100 fractions of concentrated yellow water. After the addition of CaC12, O. 220 7 fraction of ethyl formate and 0. 514 2 fraction of ethyl acetate could be obtained after distillation of the azeotrope. Finally, 92. 094 8 fractions of esterification liquid with 38 kinds of flavor- ing compound could be obtained after catalytic esterification of 100 fractions of concentrated yellow water, and the content of ethyl acetate, ethyl propionate, ethyl- butyrate, ethyl valerate, ethyl lactate and ethyl bexanoate were as much as 142.9, 22.2, 54.2, 3.3,75.4 and 158.9 g/L, respectively. [ Conclusion] Top-grade Luzhou-flavor liquor could be made by mixing 6.5 fractions of common liquor with acetaldehyde, ethyl formate, ethyl acetate and esterification liquid which were ob- tained from 1 fraction of yellow water. Therefore, the yellow water has a great recycling value, and it tells us that the technique of extracting liquor flavorings from yellow water has tremendous market value.

Ethylene Stimulation of Rubberwood （Hevea brasiliensis） Increases the Water Permeability of Lumber

Hevea brasiliensis Muell. Arg. is an important industrial crop for natural rubber production. Latex biosynthesis occurs in the cytoplasm of highly specialized latex cells and latex bleeds out when the bark is tapped. Ethylene stimulation acts by increasing latex flow to the cells of inner bark from the latex cells, increasing yield and may affect the physical properties of rubberwood. The aim of this work was to assess the permeability properties of ethylene treated rubberwood （TRW） relative to untreated rubberwood （URW）, because in wood industrial technology, permeability relates to bondability and wood preservative treatments. The Hevea samples were of PRIM 600 strain, from 20-25 years old rubber trees. The TRW rubber trees had been stimulated by ethylene gas for six years. The rubberwood specimens were collected at a single plot of plantation to minimize variations in soil fertility, environmental exposures and silvicultural treatments at Tumbon Chaibury, Amphor Chaibury, Suratthani Province, Thailand. The moisture contents （MC） of fresh rubberwood were significantly different （P 〈 0.05） at 75% for TRW and 64% for URW. The permeability experiment followed Darcy＇s law, and the hydrostatic pressure was controlled. The average 0.005 Darcy water permeability of TRW was significantly higher than the 0.001 Darcy for URW. Water absorptions during 4 h water immersion of rubberwood blocks differed significantly, and TRW had higher absorption than URW also across 6 d of immersion. Scanning electron microscope （SEM） imaging showed anatomical effects that contribute to the fivefold permeability increase.

The Optimization of Synthesizing Graft Copolymer of Starch with Vinyl Monomers

The graft copolymerization of acrylamide （ AM ） / acrylic acid （ AA ） onto starch （ St- g-pAA and St-g-p（AA-co-AM） ） was carried out using an orthngonal test method. The combined effects of different reaction conditions on the water absorbency of the graft copolymers were optimized through mathematical statistical methods of range and square variance analysis. The maximum water absorbency was obtained when the ratio of dried starch to distilled water was 1 ： 8 （ w/w ）, the ratio of starch to monomer 1 ： 6 （ w/w ）, the initiator concentration 4.40 × 10^-3 mol/L, the crosslinker concentration 10.86 × 10^-2 mol/L, and the basicity to AA 0. 70（ mol/mol ）. Both the graft copolymers have an excellent water absorption capacity in distilled water aact in 0. 9wt% NaCl solution. It was also found that in distilled water the water absorbency of St-g-pAA was higher than that of St-g-p（ AA-co-AM） , while in 0.9wt% NaCl solution, the situation was just the reverse. The correlation between the water absorbeacy anct the nature of the solution anct the properties of the copolymers, which is related to the properties of the monomers, was discussed. The grafting of AA ancl AM onto starch was confirmed by the IR spectra of St-g-pAA and St-g-p（ AA-co-AM）.

Preparation, Swelling and Antibacterial Behaviors of N-Succinyl Chitosan-g-Poly(Acrylic Acid-co-Acrylamide) Superabsorbent Hydrogels

Superabsorbent hydrogels were prepared successfully from N-succinyl chitosan grafted poly（acrylic acid-co-acrylamide）. The potassium persulfate（KPS）, N, N＇-methylenebisacrylamide（MBA） were used as the initiator and crosslinker, respectively. Fourier transform infrared spectroscopy（FTIR） and scanning electron microscopy（SEM） were used to confirm the porous network structure of superabsorbent hydrogel. The effects of reaction parameters on the swelling behaviors of the superabsorbent hydrogels were investigated. The results indicated that water absorbency increased first, and then decreased gradually with the increase in the contents of monomer（AA＋AM）, KPS, MBA or acrylamide. The product had excellent water absorbency of 1375 g/g in distilled water and 83 g/g in 0.9wt% NaCl solution. Simultaneously, the superabsorbent hydrogels were p H sensitive. The antibacterial activities of the hydrogels against Escherichia coli（E. coli） were improved effectively because of polyamidoamine（PAMAM） dendrimer absorbed in the hydrogels.

DETERMINATION OF SUPERFICAL ABSORBED DOSE FROMEXTERNAL EXPOSURE OF WEAKLY PENETRATING RADEATIONS

The methods of determining the superficial absorbed dose distributions in a water phantom by means of the experiments and available theories have been reported. The distributions of beta dose were measured by an extrapolation ionization chamber at definite depthes corresponding to some superficial organs and tissues such as the radiosensitive layer of the skin, cornea, sclera, anterior chamber and lens of eyeball.The ratios among superficial absorbed dose D (0.07) and average absorbed doses at the depthes 1,2,3,4,5 and 6 mm are also obtained with Cross's methods. They can be used for confining the deterministic effects of some superficial tissues and organs such as the skin and the components of eyeball for weakly penetrating radiations.

Degradation products of different water content sevoflurane in carbon dioxide absorbents by gas chromatography-mass spectrometry analysis

Background Sevoflurane is currently used as a volatile inhalation anesthetic with many clinical advantages. A representative degradation product, compound A, was quantitatively measured to investigate whether there are different reactions between two kinds of water content sevoflurane formulations with different carbon dioxide （CO2） absorbents.

Effect of biochar aging in agricultural soil on its wetting properties and surface structure

Biochar wettability and ability to accumulate moisture inside the porous space are crucial for improving soil fertility,regulating soil water balance,and regulating nutrients.However,a long-term interaction of biochar with agricultural soils may drastically alter the wetting properties and,eventually,influence water holding capacity and the structure of soils.In this work,the structure and wetting properties of biochar samples after 6-year long exposure to a sandy loam Spodosol with a crop rotation and mineral fertilizers application were studied.It was found that the elemental composition of the aged biochars was richer and more"soil-like",which is explained by the presence of the mineral crust on the biochar surface.The temporal evolution of biochar in the soil without any mineral fertilizer application resulted in significant improvement of its surface wettability due to the effects of various environmental factors.The lateral surface of biochar after 6-year interaction with the soil changes into a loose porous layer in a form of grooved base filled with adherent mineral soil and clay particles.Contrary,the application of the mineral fertilizer to the soil resulted in decreased wettability of the biochar lateral surfaces due to a decrease in the polar component of surface energy and the crusting of the surface with fine material,which blocks the pore space of the biochar.As a result,water capacity of the biochar from the treatment with the fertilizer decreased compared to the biochar samples collected from the soil without the fertilizer application.The radial biochar surfaces of both types of samples collected from the soil were open vessels filled with soil particles that slow down complete wetting and water absorption.The treatment of the biochar samples with surfactants drastically increased wettability of lateral surface and water absorption capacity of control samples as compared to the samples collected from the soil.The obtained results support the idea that the hydrophilisation of biochar caused by the adhesion of soil particles and treatment of its pore surface with surfactants,can improve the water-holding capacity of the sandy loam Spodosol in the plant-available range of soil water.

Development of Polymer Materials for Combating Desertification

Aiming respectively at the two problems in desertiflcation areas, namely water shortage and serious soil erosion, the polymer materials for combating desertiflcation may be classified as water absorbing-retaining polymers (WARPs) and sandy soil stabilizing polymers (SSSPs). Their further classifications and current researcfl situations were introduced. It is suggested that the major hindrancefor their wide appHcation is the high cost. The authors' newest research resuits on cutting cost and enhancing ef...