Enhanced Luminescence of Yb3+ Ions Implanted to ZnO through the Selection of Optimal Implantation and Annealing Conditions

Rare earth-doped zinc oxide (ZnO:RE) systems are attractive for future optoelectronic devices such as phosphors, displays, and LEDs with emission in the visible spectral range, working even in a radiation-intense environment. The technology of these systems is currently under development, opening up new fields of application due to the low-cost production. Ion implantation is a very promising technique to incorporate rare-earth dopants into ZnO. However, the ballistic nature of this process makes the use of annealing essential. The selection of implantation parameters, as well as post-implantation annealing, turns out to be non-trivial because they determine the luminous efficiency of the ZnO:RE system. This paper presents a comprehensive study of the optimal implantation and annealing conditions, ensuring the most efficient luminescence of RE³⁺ ions in the ZnO matrix. Deep and shallow implantations, implantations performed at high and room temperature with various fluencies, as well as a range of post-RT implantation annealing processes are tested: rapid thermal annealing (minute duration) under different temperatures, times, and atmospheres (O₂, N₂, and Ar), flash lamp annealing (millisecond duration) and pulse plasma annealing (microsecond duration). It is shown that the highest luminescence efficiency of RE³⁺ is obtained for the shallow implantation at RT with the optimal fluence of 1.0 × 10¹⁵ RE ions/cm² followed by a 10 min annealing in oxygen at 800 °C, and the light emission from such a ZnO:RE system is so bright that can be observed with the naked eye.

Heavy metals effect on breast cancer progression

Background

Breast cancer is the most frequent localization of malignant process in American women and women of European countries. To date it is not possible to control the morbidity growth due to lack of effective ways of primary prevention. Comparing the incidence of breast cancer in developed countries with the countries of Asia and Africa, there is the fact of population predominance lesion in more urbanized countries. This suggests that the environment along with other factors, occupies a significant place in the initiation and progression of breast neoplasia. The impressive rates of industrial development led to the pollution of soil, surface water and, as a consequence, food by heavy metal salts.

The purposes of this paper are as follows: the chemical composition determination of neoplastic breast tissue, evaluation of the DNA methylation level, study of prognostic-important receptors expression in the breast cancer cells, establishing linkages between all the derived indicators.

Methods

In our study we used the following methods: studying of the chemical composition of breast cancer tissue by atomic absorption spectrophotometry and energy-dispersion spectrometer; іmmunohistochemical study of ER, PR, HER2/neu, p53, Ki-67, E-cadherin and MGMT receptors; DNA extraction and investigation by oscillating infrared spectroscopy method.

Results

The total amount of heavy metals in breast cancer tissue ranged from 51.21 × 10⁻³ to 84.86 × 10⁻³ μg/kg. We have got the following results: the growth of heavy metals in neoplastic tissue is accompanied with the increase of HER2/neu, p53, Ki-67, MGMT expression and decrease of ER and PR expression. The increment of pathological DNA methylation is accompanied with the increasing amount of heavy metals in tumor tissue.

Conclusions

Heavy metals through different pathogenetic links stimulate the progression of breast cancer and reduce its sensitivity to treatment. DNA of tumor tissue has a different level of methylation which changes with the amount of heavy metals in cancer cells. This is displayed on the synthesis of prognostically important receptors in neoplastic tissue.

Native Language Education in Ukraine and the Ukrainian Diaspora: Comparative Analysis at the Turn of the Century

The trends of development of native language education of Ukrainians living in Ukraine,the USA and Canada have been analyzed. They are stipulated by globalization as well asintegration processes on a global scale in the end of the 20th and at the beginning of the 21stcenturies. Their dependence on state language and language education policies in Ukraine havebeen grounded together with national consciousness of the Ukrainians whereas the westerndiaspora dependence on external (language policy in the country of residence, assimilation,assistance from Ukrainian part) and internal factors (national consciousness of Ukrainians in thediaspora, their integration into different society, functioning of native language education, publicorganizations) have also been reasoned.The functioning of institutions in the USA and Canada have been studied (parents/family –kindergartens – Ukrainian Studies Schools and Courses at Universities). Where the subjects inUkrainian Language and Systems of State Educational Institutions for young generations of theAmerican and Canadian Ukrainians are being taught.The following key trends of native language education have been distinguished: bilingualism(Russian-Ukrainian languages in Ukraine which, in general, has a negative impact on the status ofnational language. English-Ukrainian languages in the USA and Canada which is an essential partof the integration of national minorities representatives into the societies of these countries);reduction of Ukrainian language speakers in the USA and Canada as well as in Ukraine; stateassistance in language teaching for ethnic communities/minorities in Ukraine and separateCanadian provinces; seeking for efficient means and methods of teaching native language inpolytechnic / multilingual environments such as mountainous regions of the USA, Canada andUkraine.The conclusion is that despite of assimilation and migration processes in the diaspora andUkraine, the need of Ukrainian language learning is growing. This is particularly connected withthe fourth emigration wave of Ukrainians who are willing to study their own language and obtainappropriate education.