Search

This study investigates dosimetric influence and gradient-analysis of leaf-width of various Multi-leaf-collimators (MLC) from Truebeam and Halcyon linear accelerators. The leaf-width effects of Millennium120 and HD120MLC from Truebeam and SX1 and SX2 from Halcyon were studied using virtual phantom in Eclipse16.1.2 TPS. Target structures consist of bore and wave cylinders of equally spaced projected Planning target volume (PTV) of diameters ranging from 1-to-5 cm and 20 cm length. Treatment plans for all PTVs, and four different MLCs configurations from both machines were created utilizing 6MVFFF beam to deliver dose of 50Gy/25# using IMRT and VMAT. Plans were evaluated using plan quality indices including dose conformity, homogeneity, gradient radius, and Monitor-unit (MU). Also, dose gradients were analyzed by estimating distinct integral volume V D% and paired-t-tests were performed to evaluate statistical differences. All the plan satisfied the minimum criteria of D 95 % ≥prescription dose and V 107 % ≤2cc. Mean conformity and homogeneity indices for SX1MLC(CI = 0.680,HI = 0.022) were found significantly higher and lower than SX2(CI = 0.746,HI = 0.016), Millennium120 (CI = 0.739,HI = 0.012), and HD120MLC(CI = 0.745,HI = 0.017), respectively. However, CI and HI for SX2, Millennium120, and HD120MLC found comparable. Gradient radius enclosing 50 % of isodose observed maximum and minimum for SX1 and HD120MLC, respectively. Plan MUs for Truebeam MLCs were found approximately 25 % higher than Halcyon MLCs. Dose distribution generated using SX2 and Millennium120 found comparable, however p ≤ 0.05 ascertained substantial differences among SX1, Millennium120, and HD120MLC. MLC leaf-width influences intensity-modulation and significantly alters dosimetric outcome depending on the magnitude of the leaf-width. HD120MLC does not show much significant advantages over SX2 and Millennium120 except gradient control. Halcyon SX1MLC produces least effective plan compared to all other MLC types. However, SX2 and Millennium120 can produce plans of comparable quality except plan MUs difference. [ABSTRACT FROM AUTHOR]

Bio-fertilizers are in the present more and more of interest as alternative nutritive inputs. This research aim was to test different doses of yeast and caffeine on pepper growth and chlorophyll content. The experiment in controlled conditions consisted of 8 phytocosms treatments with 3 yeast and caffeine doses 1%, 2%, and 3%, one mixed treatment (2%), and the control treatment in five replications. The yeast addition promoted all the tested morphological parameters especially the middle dose tested. Caffeine treatments induced a slow growth of pepper vegetative period, even a delayed development compared with the control treatment. In conclusion, the mixed treatment was the most efficient pepper bio-fertilizer and provided the highest values of leaf length, width, seedling height, and also total chlorophyll content. [ABSTRACT FROM AUTHOR]

Receptor-like kinases (RLKs) are important for plant growth, development and defense responses. The S-receptor protein kinases (SRKs), which represent an RLK subfamily, control the self- incompatibility among Brassica species. However, little information is available regarding SRK functions in rice. We identified a gene OsSRK1 encoding an atypical SRK. The transcript of OsSRK1 was induced by abscisic acid (ABA), salt and polyethylene glycol. OsSRK1 localized to the plasma membrane and cytoplasm. Leaf width was increased in OsSRK1 -overexpression (OsSRK1 -OX) transgenic rice plants, likely because of an increase in cell number per leaf. Furthermore, the expression levels of OsCYCA3-1 and OsCYCD2-1, which encode positive regulators of cell division, were up-regulated in leaf primordium of OsSRK1 -OX rice plants relative to those in wild type. Meanwhile, the expression level of OsKRP1 , which encodes cell cycle inhibitor, was down-regulated in the OsSRK1 -OX plants. Therefore, it is deduced that OsSRK1 regulates leaf width by promoting cell division in the leaf primordium. Additionally, Os SRK1 -OX plants exhibited enhanced ABA sensitivity and salt tolerance compared with wild type. These results suggest that OsSRK1 plays important roles in leaf development and salt responses in rice. [ABSTRACT FROM AUTHOR]

Purpose To investigate the changes in quality of the volumetric modulated arc therapy (VMAT) plans with couch-shift between arcs by half of a multi-leaf collimator (MLC) leaf width. Methods A total of 22 patients with head-and-neck cancer were retrospectively selected. Since the smallest MLC leaf width was 5 mm in this study, the couch was shifted by 2.5 mm in the longitudinal-direction between arcs to increase the resolution of fluence map. A total of three types of VMAT plans were generated for each patient; the three types of plans were a two-full-arc plan without couch-shift ( NS plan ), a two-half-arc-pair plan with couch-shift ( HAS plan ), and a two-full-arc pair plan with couch-shift ( FAS plan ). Changes in the dose-volumetric parameters were investigated. Results The FAS plan showed the best plan quality for the target volumes and organs at risk compared to the NS and HAS plans . However, the magnitudes of differences among the three types of plans were minimal, and every plan was clinically acceptable. The average integral doses of the NS , HAS , and FAS plans were 160,549 ± 37,600 Gy-cc, 147,828 ± 33,343 Gy-cc, and 156,030 ± 36,263 Gy-cc, respectively. The average monitor unit of the NS , HAS , and FAS plans were 717 ± 120 MU, 648 ± 100 MU, and 763 ± 158 MU, respectively. Conclusions The HAS plan was better than the others in terms of normal tissue sparing and plan efficiency. By shifting the couch by half of the MLC leaf width in the longitudinal direction between arcs, the VMAT plan quality could be improved. [ABSTRACT FROM AUTHOR]

Abstract: Modelling leaf shape is a helpful tool for designing optimal plant shape and visualizing plant growth. The objectives of this study were to characterize the changes in patterns of leaf growth characteristics during plant development, and to model the changes in morphology of the different leaves of the rice (Oryza sativa L.) plant. In four experiments, time course observations were made on length and width of the leaves on the main stem and tillers of rice plants grown under different experimental conditions. Three experiments provided the data for developing a model. The results show that the expansion process of a single leaf on the main stem and tillers against growing degree days (GDD) followed a slow–rapid–slow pattern that was described well by a logistic function. The changes in final length of the regular leaves positioned on the main stem were described by a quadratic function that differed from the function for the flag leaf. Final leaf length on the tillers followed the ratio of the length of the simultaneously expanding leaves on the tiller to the length of the corresponding leaves on the main stem. The changes in leaf width with leaf length in relation to GDD for a single leaf on the main stem and tillers were described by a quadratic function. The general relationships between final leaf length and final leaf width for the first fully expanded leaves and the flag leaves on the main stem and tillers were described by exponential functions, whereas for the other leaves quadratic functions were needed. The effects of nitrogen level and water regime on leaf growth were quantified by using leaf-nitrogen and leaf-water contents. The model, which was validated with the independent data from the fourth experiment, predicted the time course morphological changes of leaves on the main stem and tillers of rice grown with different nitrogen and water levels well. The results of this study can lead to a more accurate description of the rice leaf in a 3D space by integrating the model with the morphogenesis models of sheath, internode and panicle within the framework of plant topology. In addition, the present leaf architecture model may be combined with a leaf emergence model and a leaf curvature model for digital representation of light interception and utilization within the leaf canopy of rice. [Copyright &y& Elsevier]