النشر العلمي

  • Using Nyquist Stability Criterion for Determining the Stability of Open and Closed-Loop Control Systems.

Abstract

     Nyquist stability criterion has been applied in in the polar plots of the open-loop transfer function. In analyzing multiple-loop systems, the inverse transfer functions sometimes may be used in order permit graphical analysis; this avoids much of numerical calculations. Nyquist stability criterion used to determine the stability of closed-loop system from its open-loop frequency response and open-loop poles. In this paper we represented some illustrative examples of the stability analysis for control system using Nyquist stability criterion. In examining the stability of open and closed-loop control systems, we found that three possibilities can occur.    

published in Gezira j. of Eng. & Applied Sci. 11-(1): 39-49 (2016)

  • Geometrical Effects of Conic Sections on the Motion of Bodies

Abstract

         The subject of dynamics is generally divided into two branches; kinematics which is concerned with the geometry of motion apart from all considerations of force, mass or energy. And kinetics which is concerned with the effects of forces on the motion of bodies. In this paper, we explained the basic geometrical concepts of the conic sections   (ellipse, parabola, and hyperbola) and their effects on the suitable kind of motion and the orbits of bodies.  

published in Gezira j. of Eng. & Applied Sci. 10-(2): 57-70 (2015)

  • Nature of Damage and Host Preferences of the Tomato Fruit Borer,Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), Wad Madeni, Sudan

Tomato fruit borer, Tuta absoluta ,is considered as one of the most economical insect pests that causes direct damage on many vegetable crops . It is considered in many countries as a quarantine pest . This study aimed to recognize the nature of damage and to evaluate the susceptibility of tomato, potato, egg plant and  sweet pepper to tomato fruit borer.  Experiments were conducted during winter seasons of 2013/2014 and 2014/2015 at the experimental farm of Gezira University, Wad Madani , Sudan . A Completely Randomize Block Design ( RCBD)  with four replications was used. Susceptibility to tomato fruit borer on leaves and fruits was estimated. The nature of damage showed initially the new emerged larvae of T. absoluta feed on the mesophyll of the leaf leaving only the epidermis intact, causing severe loss of photosynthetic capability. T. absoluta larvae feeding create a wide, irregular mine. After maturing the fully fed larvae may leave the fruit and pupate on the fruit stalk. The larvae caused  black frass on the upper surface of the leaves or near the entry hole.  Experiments revealed significant differences between the tested crops with respect to susceptibility of their leaves and fruits to tomato fruit borer . Leaves showed the highest percentage of infestation. The infestation percentages on different crops within season 2013/2014 were 7.19, 6.57, 3.04 and 1.97, while in season 2014/2015  were 7.3, 6.9, 3.9 and 2.04  for tomato, potato, egg plant and sweet pepper, respectively.  Tomato fruits showed the highest percentage of injury (5.53%) , eggplant (3.71%) , potato (2.29%) whereas  sweet pepper fruits showed no injury within season 2013/2014 and 4.95, 1.73, 3.71 and 0.70 for tomato, egg plant, potato and sweet pepper, respectively for season 2014/2015.  

 

published in 2nd Annual International Conference on Higher Education in Post- Conflict Societies

  • siRNA delivery system based on magnetic nanovectors: Development, characterization and stability evaluation

Gene therapy and particularly small interfering RNA (siRNA) is a promising therapeutic tool for treatment of various human diseases, especially cancer. However siRNA clinical applications are limited by its intrinsic properties such as short plasma half-life, lack of targeting and poor membrane permeability. Effective anticancer drug development represents the key for translation of research advances into medicines. Nanoparticles (NPs) have attracted increasing attention as siRNA carriers because of their nanometer scaled sizes, ease of functionalization and low cost. Among them, Superparamagnetic Iron Oxide Nanoparticles (SPIONs) which are highly magnetized in magnetic field, allowing both therapeutic magnetic tumor targeting and biomedical magnetic resonance imaging (Theranosis).

In this work, formulation of magnetic siRNA nanovectors (MSN) based on silanised SPIONs, chitosan and siRNA for systemic administration was developed. Since the presence of free components can change the properties of the nanovector, purification step via centrifugation was carried out. Physical, chemical and biological stability of MSN were studied and evaluated mainly through capillary electrophoresis. Nanovectors with hydrodynamic diameter and zeta potential suitable for systemic administration were produced, especially after purification. 95% of siRNA was found entrapped within the purified MSN (pMSN). pMSN showed colloidal stability at pH 7.4, effective protection of siRNA against ribonuclease degradation up to 24 hours and few siRNA release (less than 10%) at pH 7.4. These findings push toward further evaluation studies in vitro and/or in vivo, indicating the appropriateness of pMSN for cancer theranostics.

published in International Conference on Nanomedicine and Nanobiotechnology (ICONAN 2018)

  • Evaluation of some Economics Traits in Eastern Sudan Cattle Ecotypes

published in Tropentag 2018

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