Browse

You are looking at 101 - 110 of 305 items for :

  • Medical Physics x
Clear All
Open access

Stela Dermendzhieva and Semra Nejdet

Abstract

The purpose of this paper is to follow “Climate change, risks and Natural Resources“ in the curriculum of Geography of Bulgaria and the world in 9th and 10th grade and to interpret some didactic aspects.

Analysis of key themes, concepts and categories related to the environment, events and approaches to environmental protection and the environmentally sound development of sectors of the economy is didikticheski targeted. Considering the emergence and development of geo-ecological issues, their scope and their importance to the environment, systematize some species and some approaches to solving them.

Geography education in grade 9 and 10 involves acquiring knowledge, developing skills and composing behaviors of objective perception and assessment of the reality of globed, regional and local aspect.

The emerging consumer and individualistic culture snowballing globalization, are increasingly occurring global warming, declining biodiversity form new realities which education must respond appropriately.

The objective, consistency, accessibility and relevance in real terms are meaningful, logical accents. Whether and how reproduced in the study of Geography of Bulgaria and the world is the subject of research study in this report.

Geoecological structuring of topics, concepts and categories can be done in different signs. In terms of their scope are local, national or regional, and global. Matter and interdisciplinary approach, which is to reveal the unity of the “man-society-nature” to clarify the complexity of their character with a view to forming a harmonious personality with high Geoecological consciousness and culture, and the activities carried out in their study.

Open access

Asya Dragoeva, Zheni Stoyanova, Vanya Koleva and Daniela Dragolova

Abstract

Nepeta nuda subsp. nuda is a medicinal plant growing wild in Bulgaria. Different species of Nepeta genus have been reported to possess allelopathic potential. The present study was conducted to observe its phytotoxic effects on T. aestivum and C. sativus L. seeds in laboratory conditions. Nepeta water extracts (NWE) prepared from aerial parts of plants at concentrations 2, 4, 6, 8, 10, 12 and 14 g/l were tested. The rate of seed germination, the root and shoot length, fresh and dry weight of seedlings were observed after treatment with NWE. As a control served seeds treated with distilled water. Germination was not affected, but NWE showed deterioration in seedling growth. Roots were more affected than shoots. The fresh and dry weights were reduced upon treatment with the extracts tested. These negative effects were dose-dependent. The overall results indicate presence of water soluble allelochemicals in Nepeta nuda subsp. nuda.

Open access

Karthick Raj Mani, Shantanu Sapru, K. J. Maria Das and Ayan Basu

Abstract

Aim: To demonstrate a simple technique of cranio-spinal irradiation (CSI) in supine position using inter fraction moving field junctions to feather out any potential hot and cold spots.

Materials and Methods: Fifteen patients diagnosed with medulloblastoma were treated during the period February 2011 to June 2015 were included in this study. Out of fifteen patients in the study nine were male and 6 were female with a median age of 13.4 years (range 5-27 years). All the patients were positioned supine on CT simulation, immobilized using thermoplastic mask and aligned using room based laser system. Two parallel opposed lateral fields for the whole brain using an asymmetrical jaw with isocenter at C2 vertebral body. A posterior field also placed to cover the cervical and dorsal field using the same isocenter at C2. The second isocenter was placed at lumbar vertebral region to cover the remaining dorsal, lumbar and sacral region using an inter-fraction moving junction. Field-in-field and enhanced dynamic wedge used to homogeneous dose distribution when required.

Results and Discussion: In this study, we found that only two patients failed in the primary site, no radiation myelitis or recurrences in the filed junctions were reported in these fifteen patients with a median follow-up of 36.4 months. The automated sequence of treatment plans with moving junctions in the comfortable supine position negating the need for manual junction matching or junction shifts avoiding potential treatment errors and also facilitating delivery of anesthesia where necessary.

Open access

Ion I. Cotăescu

Abstract

In this report we revisit the results obtained in [1, 2] where the relativistic Aharonov-Bohm was studied for the first time. The method is based on the exact solutions of the complete (1+3)-dimensional Dirac equation of fermions moving in ideal Aharonov-Bohm (AB) rings and cylinders which are used for deriving the exact expressions of the relativistic partial currents. It is shown that these currents can be related to the derivative of the fermion energy with respect to the flux parameter, just as in the non-relativistic case. However, a new and remarkable relativistic effect is the saturation of the partial currents for high values of the total angular momentum. Based on this property, the total relativistic persistent currents at T = 0 is evaluated for rings and cylinders obtaining approximative simple closed formulas. Notice that this report brings together the texts of Refs. [1, 2] with some improvements and unitary notations.

Open access

Sergiu Lucaciu, Robert Blaga, Nicoleta Stefu and Marius Paulescu

Abstract

The fluctuation of solar radiation at ground level represents a challenge in modeling the time series of solar irradiance. A procedure for the quantification of the instability of the solar radiative regime is reported. This procedure is based on the clearness index, as the ratio of the horizontal solar irradiance measured at ground level and the estimated one at extraterrestrial level. New quantities for classifying the days from the radiative stability point of view are being introduced. A procedure for classifying days according to their stability regime as stable, variable and unstable is presented.

Open access

M. Osiac, M.A. Dinu and M.T. Udristioiu

Abstract

In this paper, the viability of laser ablation of gold target immersed in medical distillated water used to produce nanoparticles having morphological, structural and compositional properties for medical applications is explored. The morphological properties were investigated by means of scanning electron microscopy (SEM). Energy-dispersive X-ray spectroscopy (EDX) analysis was used to reveal the composition of resulting particles. The absorbance in the wavelengths range of 300-800 nm can be assigned to the small gold nanoparticles.

Open access

Iordana Astefanoaei, Ioan Dumitru and Alexandru Stancu

Abstract

The induced thermal stress in a heating process is an important parameter to be known and controlled in the magnetization process of core-shell nanowires. This paper analyses the stress produced by a laser heating source placed at one end of a core-shell type structure. The thermal field was computed with the non-Fourier heat transport equation using a finite element method (FEM) implemented in Comsol Multiphysics. The internal stresses are essentially due to thermal gradients and different expansion characteristics of core and shell materials. The stress values were computed using the thermo elastic formalism and are depending on the laser beam parameters (spot size, power etc.) and system characteristics (dimensions, thermal characteristics). Stresses in the GPa range were estimated and consequently we find that the magnetic state of the system can be influenced significantly. A shell material as the glass which is a good thermal insulator induces in the magnetic core, the smaller stresses and consequently the smaller magnetoelastic energy. These results lead to a better understanding of the switching process in the magnetic materials.

Open access

Osamu Tanaka, Takayoshi Iida, Hisao Komeda, Masayoshi Tamaki, Kensaku Seike, Daiki Kato, Takamasa Yokoyama, Shigeki Hirose and Daisuke Kawaguchi

Abstract

Visualization of markers is critical for imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI). However, the size of the marker varies according to the imaging technique. While a large-sized marker is more useful for visualization in MRI, it results in artifacts on CT and causes substantial pain on administration. In contrast, a small-sized marker reduces the artifacts on CT but hampers MRI detection. Herein, we report a new ironcontaining marker and compare its utility with that of non-iron-containing markers. Five patients underwent CT/MRI fusion-based intensity-modulated radiotherapy, and the markers were placed by urologists. A Gold Anchor™ (GA; diameter, 0.28 mm; length, 10 mm) was placed using a 22G needle on the right side of the prostate. A VISICOIL™ (VIS; diameter, 0.35 mm; length, 10 mm) was placed using a 19G needle on the left side. MRI was performed using T2*-weighted imaging. Three observers evaluated and scored the visual qualities of the acquired images. The mean score of visualization was almost identical between the GA and VIS in radiography and cone-beam CT (Novalis Tx). The artifacts in planning CT were slightly larger using the GA than using the VIS. The visualization of the marker on MRI using the GA was superior to that using the VIS. In conclusion, the visualization quality of radiography, conebeam CT, and planning CT was roughly equal between the GA and VIS. However, the GA was more strongly visualized than was the VIS on MRI due to iron containing.

Open access

Donia Ben Hassen, Sihem Ben Zakour and Hassen Taleb

Abstract

A novel scheme for lesions classification in chest radiographs is presented in this paper. Features are extracted from detected lesions from lung regions which are segmented automatically. Then, we needed to eliminate redundant variables from the subset extracted because they affect the performance of the classification. We used Stepwise Forward Selection and Principal Components Analysis. Then, we obtained two subsets of features. We finally experimented the Stepwise/FCM/SVM classification and the PCA/FCM/SVM one. The ROC curves show that the hybrid PCA/FCM/SVM has relatively better accuracy and remarkable higher efficiency. Experimental results suggest that this approach may be helpful to radiologists for reading chest images.