Difference is important operation on graph but the definition of this operation has not any logic. So, in this paper we will define new types of difference of general-graphs. The adjacency and incidence matrices of these operations will be deduce. We will introduce some theorems on these operations.

Given that the students compos a big class of the possible work force of the future of the country and the university graduates who are in a dire need of the business and income are increasing day by day and given that the private and state sectors can’t provide a job for them, it is necessary to investigate the factors affecting the students to begin a new business. (National conference of the entrepreneurship (2012). In fact, education and making readiness of the management students that want to be independence and launch a business is possible through their familiarity with the business skills and knowledge. Also, the purpose is the national development and the permanent development of the five - year program of the cultural, social and economic prediction of the country and also the twenty – year perspective .The recognition of the factors that affect on the business pattern can contribute to the occupation extent, increasing of the exploitation and the product capability of the students and reduce the unemployment extent of the graduates.

Background As one of the toxic mechanisms of nanoparticles (NPs), the reactive oxygen species (ROS) generation has been widely studied. Nevertheless, the link between GNPs and antioxidant oxidative stress markers has not been well established. So this study was aimed to evaluate the effect of gold nanoparticles (GNPs) size and exposure duration (3 and 7 days) on antioxidant and oxidative stress markers including reduced glutathione (GSH), super oxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), total antioxidant capacity and malondialdehyde (MDA) in different rat organs. Materials and methods Adult male Wistar-Kyoto rats were randomly divided into 6 groups of 5 animals each. One group served as control and received vehicle only. The 10 nm GNPs (MKN-Au-010 of concentration 0.01%) were used in this study. The GNPs electron density and homogeneity in shape and size was evaluated. Dose of 50 µl of 10 nm NPs in aqueous solution were administered to animals via intraperitoneal administration daily for exposure duration of 3 or 7 days. The rats were sacrificed 24 h after the last injection of GNPs. The specimens of liver, lung, kidney and heart were collected for biochemical analyses. Results The GPx, total antioxidant capacity, GSH and MDA levels significantly increased after intraperitoneal administration of 10 nm GNPs for exposure duration of 3 and 7 days in the organs of rats compared with the control. The GR and SOD levels significantly decreased after intraperitoneal administration of 10 nm GNPs for exposure duration of 3 and 7 days in the organs of rats compared with the control. Conclusions The NPs have the potential to interact with the biological system and cause undesirable effects. One of these damaging effects could be the disturbance in the natural balance between oxidative stress and antioxidant defense indices which in turn can lead to various pathological effects. The oxidative stress has been identified as a likely mechanism of NPs toxicity. This study demonstrates that the increased production of ROS after intraperitoneal administration of GNPs into rats might attributed to increased production of GPx, total antioxidant capacity, GSH and MDA levels, and to decrease production of GR and SOD levels.

The aim of this paperwork is to present a set of comparative corporate governance (CG) standards in some Eastern European countries including: Bulgaria, Romania, and Hungary, plus 2012 CG practices for microfinance institutions. There are strengths and weaknesses in these codes or practices which will be identified in this paperwork. Therefore, this paper not only identifies different points in latest corporate governance standard principles and systems in the above three (3) countries, but also provides with a summary of evaluation of current corporate governance systems in these above countries which may enable relevant organizations in re-evaluating their current ones. Last but not least, it aims to illustrate a limited comparative set of standards of Eastern European corporate governance, and give proper recommendations to relevant governments and institutions toward a sustainable practices in business life.

Using a one factor model, this paperwork estimates the impacts of the size of firms’ competitors in the natural gas and oil industry on the market risk level, measured by equity and asset beta, of 15 listed companies in this category. This study identified that the risk dispersion level in this sample study could be minimized in case the competitor size kept as current approximate size (measured by equity beta var of 0,129). Beside, the empirical research findings show us that asset beta min value decreases from 0,107 to 0,034 when the size of competitor doubles. Last but not least, most of beta values are acceptable except a few exceptional cases. Ultimately, this paper illustrates calculated results that might give proper recommendations to relevant governments and institutions in re-evaluating their policies during and after the financial crisis.