Browsing by Author "Mohammed, Kedir"

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    Hematological Parameters of Patients with Thyroid Dysfunction at S.t Paul‟s Hospital Millennium Medical College, Addis Ababa, Ethiopia
    (Addis Abeba University, 2021-03) Mohammed, Kedir; Negash, Mikyas(MSc, PhD candidate, Assistant Professor of Hematology and Immunohematology); Tibebu, Melatwork (MSc, PhD candidate)
    Background: Thyroid hormones have a decisive role in metabolism and proliferation of blood cells and blood cells indices. Thyroid dysfunction leads different effects on blood cells such as anemia, leukopenia, thrombocytopenia, and in rare cases causes pancytopenia. Objectives: To determine hematological parameters of patients with thyroid dysfunction at S.t Paul‟s Hospital Millennium Medical College (SPHMMC), Addis Ababa, Ethiopia, from March- August, 2020. Methods: A hospital based comparative cross sectional study was conducted from March to August, 2020, at SPHMMC, Addis, Ababa, Ethiopia. Convenient sampling technique was used for comprising of a total of 180. Participants‟ socio-demographic and clinical information was collected from hospital cards. Initially 10 ml of venous blood samples were collected in to two separated test tubes. The blood specimen in the plain tube used for measurement of TSH, T3 and T4 (Cobase e 411 immunoassay system). Sample in the EDTA tubes, used for CBC analysis (Beckman-coulter hematology analyzer). Descriptive statistics was used to express the socio demographic and clinical characteristics. Independent T test to compare mean value between the groups, binary and multiple logistic regressions were computed to assess association be-tween variables using SPSS version 20. P value less than 0.05 were taken as statistical significant. Results: Of the 180 study participants, 74(41.1%) hypothyroidism and 49(27.2) hyperthyroidism and 57(31.8%) were apparently healthy controls. Of them 137 (71.1 %) were female, most in the age group 26-39 years (84, 46.7%). The result obtained showed a statistically significant decrease in RBC count, Hb, HCT, MCV, PLT counts and MPV in thyroid dysfunction patients when compared with apparently healthy controls (p value <0.05). MCHC, RDW, WBC and NEU% were statistically significant increased (p value <0.05). MCH, MON%, EOS% and BAS%, did not showed significant difference between the groups (p value >0.05). Conclusion: Thyroid hormones have a significant influence on blood cell count and blood cell indices. This study showed that statistical significant difference in RBCs, Hb, HCT, MCV MCHC, total WBC count, neutrophils, PLT count, and MPV between patients with thyroid dysfunction and apparently healthy controls (p<0.05). But no difference showed MCH, monocytes, eosinophil and basophils between those groups (p- value > 0.05).
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    Investigation of Thermo- Structural Behavior of Ventilation Application on Rail Vehicle Disc Brake
    (Addis Ababa University, 2015-05) Mohammed, Kedir; Demiss, Alemu (PhD)
    In recent decades, disc brakes have increasingly become more popular and gradually found their ways in many different types of vehicles, ranging from light motorcycles to heavy road trucks or even trains. They offer several advantages over drum brakes, including better stopping performance (disc cooled readily), easier to control (not self-applying), less prone to brake fade, and quicker recovery from immersion, which largely contributed to their popularity. However, after long repetitive braking, brake fade could still set in and compromise the performance of a disc brake due to the change of friction characteristics caused by temperature rise and overheating of brake components. Overheated components could further lead to more problems such as thermal cracks, plastic deformation and the life span of a disc brake could be shortened as a result. Therefore, to accurately predict the temperature rise in a disc brake system is of eminent importance in the early design stage. Yet, owing to the interactions of several physical phenomena, prediction of disc brake performance is highly complicated. In this thesis, we were apply modeling to the thermomechanical behavior of the ventilated design of disc and the computational modeling is carried out using FEM .Ventilation applications on brake discs can significantly improve the brake system performance by reducing the heating of the discs. In this study, the thermal behaviors of ventilated brake disc configuration were investigated at repeated brake conditions in terms of heat generation and thermal stresses with finite element analysis. The results were compared with solid brake.