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Background: In radiotherapy, low-energy photon beams are better adapted to the treated volume, and the use of high-energy beams can reduce hot spots in the radiation therapy. Therefore, mixing low and high energies with different ratios can control the rate of hotspots, as well as the dose distribution of the target volume. Material and Methods: The percentage depth doses (PDDs) were calculated at various depths, by using a fitted double exponential equation. Then, using quality factor equation and PDD of a 10×10 cm2 field, the amount of energy equivalent to each PDD and the value of weighting factors of 6, 18 MV energies were calculated to produce different energies. To validate the mathematical model, dosimetry of 10 MV energy was used. For this purpose, PDDs and dose Profile of 10 MV obtained from the mix were compared with ones obtained from the measurement Results: The value of weighting factor of 6 MV energy required for the 10 ×10 cm2 field to create dose distribution of 15 MV energy using 6 and 18 MV energies was obtained as equal to 0.57. Comparison of percentage depth dose curves and dose profile shows good agreement with the practical measurements of 10 MV for 10×10 cm2 field using gamma index. Conclusion: The simultaneous use of high and low photon energies with different weighting factors to achieve desirable energy makes possible the treatment of tumors located at various depths without the need for different modes of energy in the accelerator leading to a decrease in the cost of the equipment and a safer treatment of the cancerous patients. Citation: Tahmasebi Birgani M. J, Chegeni N, Tahmasbi M, Hazbavi M, Hoseini S. M. Calculating Weighting Factors for Mixing Megavolt- age Photon Beams to Achieve Desirable Dose Distribution in Radiotherapy. J Biomed Phys Eng. 2019;9(3):279-284. https://doi.org/10.31661/ jbpe.v0i0.789.

"nBackground and Aims: Occupational burnout is a psychological syndrome resulting from continuous tensions which causes absence, conflict, job changing, etc. In spite of much effort done in optimizing the work conditions and satisfying the employed persons, the dentists still suffer from this incident. The purpose of this study was to determine the degree of occupational burnout in Birjand dentists and to provide an approach."nMaterials and Methods: In this descriptive-analytical study by the census method, 38 dentists were investigated using Maslach questionnaire. Average values were compared with chi-square and comparison among the groups was performed by Tukey test using SPSS software. P≤0.05 was considered as the level of significance."nResults: In this study, there were 68.4% men and 31.6% women with average age of 37.9 ±7.6 years and average work experience of 12.5±7.3 years, 15.8% single and 84.2% married. Frequency of exhaustion, intense depersonalization, and intense feeling of being unsuccessful was 21.1%, 81.6%, and 100%, respectively. There were no significant differences between occupation burnout dimensions and the other variable, such as gender, sports, marital status, and workday hours (P>0.05)."nConclusion: Protection of this stratum, providing educational programs and creating job variations are necessary for optimizing the work environment. Future studies with more sample size are suggested to determine the effect of factors.

Reaction of the Pt(II) complexes [PtMe2(pbt)], 1a, (pbt = 2-(2-pyridyl)benzothiazole) and [PtMe(C^N)(PPh2Me)] [C^N = deprotonated 2-phenylpyridine (ppy), 1b, or deprotonated benzo[h]quinoline (bhq), 1c] with benzyl bromide, PhCH2Br, is studied. The reaction of 1a with PhCH2Br gave the Pt(IV) product complex [PtBr(CH2Ph)Me2(pbt)]. The major trans isomer is formed in a trans oxidative addition (2a), while the minor cis products (2a' and 2a″) resulted from an isomerization process. A solution of Pt(II) complex 1a in the presence of benzyl bromide in toluene at 70 °C after 7 days gradually gave the dibromo Pt(IV) complex [Pt(Br)2Me2(pbt)], 4a, as determined by NMR spectroscopy and single-crystal XRD. The reaction of complexes 1b and 1c with PhCH2Br gave the Pt(IV) complexes [PtMeBr(CH2Ph)(C^N)(PPh2Me)] (C^N = ppy; 2b; C^N = bhq, 2c), in which the phosphine and benzyl ligands are trans. Multinuclear NMR spectroscopy ruled out other isomers. Attempts to grow crystals of the cycloplatinated(IV) complex 2b yielded a previously reported Pt(II) complex [PtBr(ppy)(PPh2Me)], 3b, presumably from reductive elimination of ethylbenzene. UV-vis spectroscopy was used to study the kinetics of reaction of Pt(II) complexes 1a-1c with benzyl bromide. The data are consistent with a second-order SN2 mechanism and the first order in both the Pt complex and PhCH2Br. The rate of reaction decreases along the series 1a ≫ 1c > 1b. Density functional theory calculations were carried out to support experimental findings and understand the formation of isomers.

The reaction of complex [Pt(Me)(DMSO)(pbz)], 1, (pbz = 2-(2-pyridyl)benzimidazolate) with [PtMe(Cl)(DMSO)2], B, followed by addition of bis(diphenylphosphino)acetylene (dppac), gave the novel tetranuclear platinum complex [Pt4Me4(μ-dppac)2(pbz)2Cl2], 2, bearing both the pbz and dppac ligands. In this structure, the pbz ligands are both chelating and bridging to stabilize the tetraplatinum framework. The tetranuclear Pt(II) complex was fully characterized by NMR spectroscopy, X-ray crystallography, and mass spectrometry, and its electronic structure was investigated and supported by DFT calculations.

This study presents the facile synthesis of CoO/PtPd and CoO/PtPd/reduced‐graphene oxide (r‐GO) nanocomposites, highlighting their significant role in methanol fuel cells. To create a CoO/PtPd thin film at the toluene/water interface, we employed NaBH4 to effectively reduce PtCl2(COD), PdCl2(COD), and Co (acac)3 (COD = cis,cis‐1,5‐ cyclooctadiene, acac = acetylacetonate). The two nanocomposites were analyzed using XRD, FE‐SEM, AFM, XPS, BET, and TEM techniques. In the electrooxidation of methanol in the anodic part of fuel cell, cobalt (II) oxide can serve as an oxygen source in the catalytic oxidation of carbon monoxide (CO) or it can play a role in producing the HO‐CoO intermediate to facilitate the oxidation of CO‐PtPd to carbon dioxide (CO2). This reaction can help eliminate CO, which is a common poison for Pt‐based catalysts in methanol oxidation. Our research reveals significant improvements in current densities and catalyst tolerance when using the CoO/PtPd/r‐GO nanocomposite thin film. The observed current density for CoO/PtPd/r‐GO is 263.33 mA.cm−2, surpassing the reported value of 30.00 mA.cm−2 for PtPd/r‐GO. The jf/jb ratios, commonly used to evaluate catalyst tolerance, are approximately 2.80 for CoO/PtPd and 4.98 for CoO/PtPd/r‐GO, in contrast to ratios larger than 0.99 for ETEK Pt and 0.58 for other types of commercial Pt/C. These findings indicate that the CoO/PtPd/r‐GO thin film exhibits enhanced catalytic performance and improved tolerance to CO poisoning. Furthermore, the power output calculated for CoO/PtPd/r‐GO is 104.5 mW·cm−2, which is comparable to the reported value of 48.03 mW·cm−2 for commercial Pt/C. These results demonstrate the potential of the CoO/PtPd/r‐GO nanocomposite thin film as a promising alternative to traditional catalyst materials in methanol fuel cells. [ABSTRACT FROM AUTHOR]

MgAl2O4 spinel matrix nanocomposite with TiC, AlTi3, and Al2O3 was directly fabricated using the mechanical alloying (MA) method with Mg, TiO2, Al, and graphite as the starting powder mixture. This methodology was used to synthesize magnesium aluminate spinel (MSA) matrix nanocomposite with having the advantage of no subsequent heat treatment. The mixture of the powders was milled at room temperature using a high-energy planetary ball mill with a vial rotation speed of 400 rpm in the air. The phases and morphological analysis after the MA process were characterized by X-ray diffraction and scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS). Followed by 20 h of ball-milling, all the desired phases of MgAl2O4, TiC, AlTi3, and Al2O3 appeared in XRD results, and also a small fraction of raw materials remained. The major reactions to synthesize MgAl2O4/TiC-AlTi3-Al2O3 spinel matrix nanocomposite were the reduction of TiO2 by Al and Mg. [ABSTRACT FROM AUTHOR]

Cheese is able to transport live probiotics due to its dry matter, fat, and higher pH than yogurt-like products. According to health organizations' emphasis on promoting the consumption of healthy dairy products and consumers' desire to eat healthier foods, in this study, the feasibility of producing probiotic UF cheese containing probiotic strains of Bifidobacterium bifidum sp. IR007-113 and Enterococcus faecium sp. IBRC-M 10836 as a single or combined study was investigated. The experimental cheeses used in this study include A: UF cheese as a control sample, B: probiotic UF cheese containing Bifidobacterium bifidum, C: probiotic UF cheese containing Enterococcus faecium, and D: probiotic UF cheese containing a combination of Bifidobacterium bifidum and Enterococcus faecium strains. Viability of probiotic organisms on the basis of log cfu/g and aroma compounds including (acetaldehyde, diacetyl, acetone, and acetic acid all in micrograms per gram) was assessed during the 60-day ripening period. The results showed that the probiotic bacterial population decreased during the 60-day storage period. However, at the end of the storage period, all experimental cheeses contained probiotic strains above 106 cfu/g. The acetaldehyde compound increased during the 60-day storage period, and diacetyl, acetoin, and acetic acid contents decreased during the 60-day storage period except for the control sample. A total of 12 free fatty acids were identified in Iranian probiotic UF white cheese, which had the highest concentration of palmitic acid among saturated fatty acids and oleic acid among unsaturated fatty acids. The sensory scores of flavor increased during the 60-day storage period. Texture sensory scores of all experimental cheeses decreased during the storage period. In terms of acceptability, all experimental cheeses showed an increasing trend. In general, the results showed that it is possible to produce UF probiotic cheese with minimal adverse effects on quality characteristics and sensory acceptability. Also, treatment D had relatively better characteristics compared to other cheese variants. [ABSTRACT FROM AUTHOR]

The GTN micromechanical fracture model is frequently used to predict the ductile fracture. This model is based on the microscopic mechanism of void nucleation, growth and coalescence in ductile material. GTN model includes many parameters that need to be precisely calibrated in order to obtain the maximum accuracy. In this study, an indirect approach is used to determine the GTN model parameters of a NiTi alloy by using the response surface method, RSM. This method is implemented in combination with the polynomial regression method. A quadratic polynomial equation is employed to obtain a relationship between the experimental results of smooth and notched round bar tensile tests with GTN model parameters. Furthermore, the genetic algorithm technique is used to find the tuned values of the parameters by minimizing the difference between the numerical and experimental responses. Compared with experimental results, simulations with the calibrated parameters could precisely predict the NiTi fracture process. [ABSTRACT FROM AUTHOR]