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Open access

Duraisamy Velmurugan, Masilamany Santha Alphin and Benedict Jain AR Tony

Abstract

Background: Implant thread profile plays a vital role in magnitude and distribution of contact stresses at the implant-bone interface. The main goal of this study was to evaluate the biomechanical effects of four distinct thread profiles of a dental implant in the mandibular premolar region.

Methods: The dental implant represented the biocompatible Zirconia material and the bone block was modelled as transversely isotropic and elastic material. Three-dimensional finite element simulations were conducted for four distinct thread profiles of a dental implant at 50%, 75%, and 100% osseointegration. An axial static load of 500 N was applied on the abutment surface to estimate the stresses acting within the bones surrounding the implant.

Results: Regions of stress concentration were seen mostly along the mesiodistal direction compared to that in the buccolingual direction. The cortical bone close to the cervical region of the implant and the cortical bone next to the first thread of the implant experienced peak stress concentration. Increasing the degree of osseointegration resulted in increased von-Mises stresses on the implant-cortical transition region, the implant-cancellous transition region, the cortical bone, and the cancellous bone.

Conclusion: The results show that the application of distinct thread profiles at different degrees of osseointegration had significant effect on the stresses distribution contours in the surrounding bony structure. Comparing all four thread profiles, a dental implant with V-thread profile induced lower values of von-Mises stresses and shear stresses on the implant-cortical transition region, implant-cancellous transition region, cortical bone, and cancellous bone.

Open access

Karthick Raj Mani, Md Anisuzzaman Bhuiyan, Md. Shakilur Rahman and S. M. Azharur Islam

Abstract

True Beam medical linear accelerator is capable of delivering flattening filter free (FFF) and with flattening filter (WFF) photon beams. True Beam linear accelerator is equipped with five photon beam energies (6 FFF, 6 WFF, 10 FFF, 10 WFF and 15 WFF) as well as six electron beam energies (6 MeV, 9 MeV, 12 MeV, 15 MeV and 18 MeV). The maximum dose rate for the 6 WFF, 10 WFF and 15 WFF is 600 MU/min, whereas 6 FFF has a maximum dose rate of 1400 MU/min and 10 FFF with a maximum dose rate of 2400 MU/min. In this report we discussed the open beam dosimetric characteristics of True Beam medical linear accelerator with FFF and WFF beam. All the dosimetric data (i.e. depth dose, cross-line profiles, diagonal profiles, output factors, MLC transmission, etc.) for 6 MV, 6 FFF, 10 MV, 10 FFF and 15 MV were measured and compared with the published data of the True Beam. Multiple detectors were used in order to obtain a consistent dataset. The measured data has a good consistency with the reference golden beam data. The measured beam quality index for all the beams are in good agreement with the published data. The percentage depth dose at 10 cm depth of all the available photon beams was within the tolerance of the Varian acceptance specification. The dosimetric data shows consistent and comparable results with the published data of other True Beam linear accelerators. The dosimetric data provide us an appreciated perception and consistent among the published data and may be used for future references.

Open access

Déte van Eeden and Freek C.P. du Plessis

Abstract

Monte Carlo (MC) simulation is the gold standard for dose calculation. An accurate mathematical source model can be used for the radiation beams. Source models can consist of sub-sources or fewer sources with data that need to be measured. This can speed up treatment plan verification without the need for a full simulation of the radiation treatment machine.

Aims: This study aimed to construct a novel hybrid source model for 6 MV photon beams for an Elekta Synergy accelerator and to commission it against measured beam data and treatments plans.

Methods and Material: The model comprised of a circular photon and planar electron contamination source. The modified Schiff formula provided off-axis variable bremsstrahlung spectra. Collimation and scatter were modelled with error functions. An exponential function modelled the transmitted fluence through the collimators. The source model was commissioned by comparing simulated and measured MC data. Dose data included profiles, depth dose and film measurements in a Rando phantom. Field sizes ranged from 1 × 1 cm2 to 40 × 40 cm2.

Results: Regular, wedged and asymmetrical fields could be modelled within 1.5% or 1.5 mm. More than 95% of all points lie within 3% or 3 mm for the multi-leaf collimators contours data. A gamma criterion of 3% or 3 mm was met for a complex treatment case.

Conclusions: The two sub-source model replicated clinical 6 MV Elekta Synergy photons beams and could calculate the dose accurately for conformal treatments in complex geometries such as a head-and-neck case.

Open access

Duong Thanh Tai, Luong Thi Oanh, Nguyen Dong Son and Truong Thi Hong Loan

Abstract

Introduction: Jaws-Only Intensity modulated radiation therapy (JO-IMRT) is a technique uses the collimator jaws of the linear accelerator (LINAC) to delivery of complex intensity patterns. In previous studies, pretreatment patient specific quality assurance for those JO-IMRT were also performed using ionization chamber, MapCHECK2, and Octavius 4D and good agreements were shown. The aim of this study is to further verify JO-IMRT plans in 2 different cases: one with the gantry angle set equal to beam angle as in the plans and the other with gantry angle set to zero degree.

Materials and Methods: Twenty-five JO-IMRT, previously verified, were executed twice for each plan. The first one used a real gantry angle, and the second one used a 0° gantry angle. Measurements were performed using Octavius 4D 1500.

Results: The results were analyzed using Verisoft software. The results show that the Gamma average was 97.32 ± 2.21% for IMRT with a 0° gantry angle and 94.72 ± 2.67% for IMRT with a true gantry angle.

Conclusion: In both cases, gamma index of more than 90% were found for all of our 25 JO-IMRT treatment plans.

Open access

Loretta Mancinelli, Francesco Ragonese, Samuela Cataldi, Maria Rachele Ceccarini, Rossana G. Iannitti, Cataldo Arcuri and Bernard Fioretti

Abstract

Agmatine has been functionally characterized as an important hormone and co-neurotransmitter in mammals. Given its ability in binding Imidazoline sites, a regolatory site of monoaminoxydase, it has been suggested to be involved in many neurological aspects. However, its inhibitory effect on this enzyme still remains an unanswered question. This present study is aimed to asses whether different experimental conditions could affect the agmatine action on monoaminoxydase activity. We demonstrate that the monoaminoxydase inhibition by agmatine is obtained under alkaline conditions and a long time of incubation. No inhibitiory action was found for shorter times of reaction at elevated pH, or at neutral condition and long time of incubation. No inhibition was also detected by substituting the monoamineoxydase substrate tyramine with kynuramine, however, while in these conditions a remarkable inhibition was shown by two aminoxydase inhibitors tranylcypromine and idazoxan. Herein, we discuss a mechanism model and the functional consequences of agmatine action on monoaminoxydase.

Open access

Orsolya Borsai, Mohamad Al Hassan, Monica Boscaiu, Radu E. Sestras and Oscar Vicente

Abstract

Drought and soil salinity are at present the major factors responsible for the global reduction of crop yields, and the problem will become more severe in the coming decades because of climate change effects. The most promising strategy to achieve the increased agricultural production that will be required to meet food demands worldwide will be based on the enhancement of crop stress tolerance, by both, traditional breeding and genetic engineering. This, in turn, requires a deep understanding of the mechanisms of tolerance which, although based on a conserved set of basic responses, vary widely among plant species. Therefore, the use of different plant models to investigate these mechanisms appears to be a sensible approach. The genus Portulaca could be a suitable model to carry out these studies, as some of its taxa have been described as tolerant to drought and/or salinity. Information on relevant mechanisms of tolerance to salt and water stress can be obtained by correlating the activation of specific defence pathways with the relative stress resistance of the investigated species. Also, species of the genus could be economically attractive as ‘new’ crops for ‘saline’ and ‘arid’, sustainable agriculture, as medicinal plants, highly nutritious vegetable crops and ornamentals.

Open access

Olga G. Babak, Natalia A. Nekrashevich, Konstantsia K. Yatsevich, Sergey V. Malyshev and Alexander V. Kilchevsky

Abstract

To develop tomato hybrids and varieties with a high fruit quality, we gradually solved the following tasks: development of DNA-marking methods for long shelf life genes; the genes modifying the biosynthesis of carotenoids and their composition; testing of the elaborated methods on the developed breeding material; the selection of samples with different allelic composition of fruit quality genes; the development of F1 hybrids using the method of successive crosses and their study; the selection of tomato forms by DNA-typing methods with target genes in F2 populations to develop valuable breeding samples; the study of carotenoids’ accumulation peculiarities and their inheritance.

We used DNA-identification methods for fruit quality genes: nor, rin, norA (long shelf life), B, ogc, hp2dg, gf-3 (carotenoid content). The tomato hybrids, combining two pigment content genes and one long shelf life gene and the model forms with different combinations of fruit quality genes (B/rin/gf-3, B/rin/hp2dg; B/nor/gf-3, B /nor/hp2dg; оgc/rin/gf-3, оgc/rin/hp2dg; оgc/nor/gf-3, оgc/nor/hp2dg) in a homozygous state were developed.

Use of the developed accessions with carotenoid content genes (ogc/hp2dg, B/hp2dg) as maternal forms and the accessions with complex fruit quality genes (ogc/hp2dg/nor, ogc/hp2dg/rin, B/hp2dg/nor, B/hp2dg/rin, ogc/gf-3/nor, ogc/gf-3/rin, B/gf-3/rin, B/gf-3/nor) as paternal forms for hybridization contributes to high accumulation of carotenoids and a lond period of fruit storability.

Open access

Martin Vanek, Filip Mravec, Martin Szotkowski, Dana Byrtusova, Andrea Haronikova, Milan Certik, Volha Shapaval and Ivana Marova

Abstract

Red yeast Cystofilobasidium capitatum autofluorescence was studied by means of confocal laser scanning microscopy (CLSM) to reveal distribution of carotenoids inside the cells. Yeasts were cultivated in 2L fermentor on glucose medium at permanent light exposure and aeration. Samples were collected at different times for CLSM, gravimetric determination of biomass and HPLC determination of pigments. To compare FLIM (Fluorescence Lifetime Imaging Microscopy) images and coupled data (obtained by CLSM) with model systems, FLIM analysis was performed on micelles of SDS:ergosterol and SDS:coenzyme Q with different content of ergosterol and coenzyme Q, respectively, and with constant addition of beta-carotene. Liposomes lecithin:ergosterol:beta-carotene were investigated too. Two different intracellular forms of carotenoids were observed during most of cultivations, with third form appeared at the beginning of stationary phase. Observed behavior is probably due to formation of some kind of carotenoid protective system in membranes of different compartments of yeast cell, especially cytoplasmic membrane.

Open access

Miroslav Ondrejovič and Stanislav Miertuš

Abstract

The paper presents main results and recommendations of the recent European Workshop dedicated to the evaluation of current state and prospects for Biotechnology with the attention to Central and European countries. The contribution of Biotechnology to the RIS3 strategy is also briefly presented. It is believed that there is still insufficient integration of research and innovation, especially in Central and Eastern European countries. Another problem is the weak interest and lack of mechanisms for the entry of potential investors into biotechnology capital-intensive areas. Series of proposals and recommendations coming from the Workshop on how to increase the regional cooperation in the field of Biotechnology is briefly described together with the potential role of international institutions (JRC-EC, CEI, ICGEB, EBTNA) in such cooperation.