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Article
Theoretical Analysis of Coupling Constant, Longitudinal Modes, and Threshold Gain for Coupled-Cavity Semiconductor Lasers

Authors: Mohammed A. Mahdi --- Kadhim A.hubeatir --- Razi Jabur Al-Azawi
Journal: Journal of Engineering and Sustainable Development مجلة الهندسة والتنمية المستدامة ISSN: 25200917 Year: 2009 Volume: 13 Issue: 3 Pages: 1-12
Publisher: Al-Mustansyriah University الجامعة المستنصرية

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Abstract

A theoretical analysis of the coupled-cavity semiconductor laser requiers simultaneous consideration of the gain and loss in the two cavities after taking into account thier mutual optical feedback. Is wavelength-independent (and hence the same for all Fapry-perot (FP)), in a coupled-cavity laser the effective facet loss becomes different.

التحليل النظري لتزاوج التجويف لليزر أشباه الموصلات والمتضمن التزاوج في الربح والخسارة بين فجوتين بعد الأخذ بنظر الاعتبار للتغذية العكسية البصرية. حيث إن هذا التزاوج لا يعتمد على الطول الموجي, في التزاوج للتجويف الليزري تكون الخسارة مؤثرة.

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Article
Study of Changes in Structural and Electrical Properties of Thin Film After Irradiation It by Laser
دراسة التغير في الخواص التركيبية و الكهربائية لغشاء مشعع بالليزر

Authors: Mohammed A. Mahdi --- Shams B. Ali --- Farah Samir
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2009 Volume: 27 Issue: 16 Pages: 2894-2902
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

This research studied the effective of irradiation by laser on structure and electrical properties of thin film such as lead sulphid PbS, so in the beginning the film has amorphous structure and when irradiation by laser (annealed) the structure properties would change and the no. of peak appeared with different modes but the mode(200) still has large intensity compared with another modes, and the grainsize increased with increased the time of irradiation to become (7.5 to 16)nm, and for the electrical properties the film has linear ship between voltage and current, and the conductivity increased when the time of irradiation.

يتناول البحث دراسة تأثير التشعيع بالليزر على الخصائص التركيبية و الكهربائية لغشاء مثل كبريتيد الرصاص حيث يظهر تركيب عشوائي لكن يأخذ بالتبلور و ظهور المادة و بروز عدد من القمم بعد التعرض إلى أشعة الليزر و يلاحظ ظهور النمط ( 200 ) بالشدة الأكبر بين القمم , و يلاحظ أيضا أن متوسط الأحجام الحبيبية تزداد تدريجياً بزيادة زمن التعرض إلى 16 ) إضافة إلى إن الغشاء يمتاز بخصائص خطية مابين التيار و – 7.5) nm الليزر لتزداد منالفولتية و يزداد مقدار التيار المار بزيادة زمن التعرض إلى الليزر حيث تزداد التوصيلية الكهربائية على حساب المقاومية الكهربائية.


Article
Dynamic Behavior of Directly Modulated Semiconductor Laser Utilizing Optical Feedback

Author: *Mohammed A. Mahdi, *Mohammed J. AbdulRazzaq, **Zainab A. Kadhim
Journal: Albahir journal مجلة الباهر ISSN: 23125721 Year: 2016 Volume: 4 Issue: 7+8 Pages: 109-115
Publisher: Shiite Endowment ديوان الوقف الشيعي

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Abstract

In this work, dynamical behavior of directly modulated semiconductor laser utilizing opticalfeedback has been simulated using MATLAB software package. The results show that the carrierdensity and photon numbers have been increased with external optical feedback (externalcavity). The effect of external mirror reflectivity on the output power has been studied and it’sfound that as the reflectivity increased the output power was increased. Also, the effect of distancebetween semiconductor laser cavity and the optical external cavity has been studied andthe maximum output power has been obtained at an external length of (0.7- 0.75) cm.

في هذا العمل، تمت محاكاة السلوك الديناميكي في ليزر أشباه الموصلات ذات التضمين المباشر باستخدام التغذية العكسية البصرية باستخدامبرنامج ماتلاب. أظهرت النتائج أن كثافة حاملات الشحنة وعدد الفوتونات تزداد عند استخدام التغذية العكسية. تمت دراسة تأثير انعكاسيهالمرأة الخارجية على القدرة الخارجة، ووجد أن عند ازدياد انعكاسية المرأة يزداد خرج الليزر أيضاً. كذلك تم دراسة تأثير المسافة بين منظومة الليزر75,0 ( سم. - والمرأة الخارجية، حيث وجد أن أعظم قدرة يمكن الحصول عليها عند مسافة بحدود ) 7,0


Article
Evaluation of the efficacy of ultrasound in the diagnosis of cervical lymphadenopathy

Authors: Shahad D. Ali --- Taghreed F. Zaidan --- Mohammed A. Mahdi
Journal: Journal of baghdad college of dentistry مجلة كلية طب الاسنان بغداد ISSN: 16800087 Year: 2018 Volume: 30 Issue: 3 Pages: 59-67
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: Cervical lymph nodes are prone to involved by a number of pathologic processes. They are common sites for lymphoma, metastasis, and reactive enlargement in a number of conditions.Aims of the study:-Clinical evaluation of patients with cervical lymphadenopathy. Differentiation between benign and malignant lymph nodes by means of ultra sounds (US) and Correlate the US findings with cytological and/or histopathological findings of cervical lymph nodes.Subjects, Materials and Methods:-The present study was carried out over a period of 6 months and included 81 patients of different age groups presenting with cervical lymphadenopathy. Each patient was examined clinically, then comprehensive sonographic examination of the neck for cervical lymph nodes (L.Ns) was performed using ultrasound machine (GE Wipro Proseries). The scanning was performed with the patient in the supine position, and with the neck hyperextended using a pad or pillow under the shoulders in order to provide optimum exposure of the neck. The parameters considered in this study include: site, long axis (L), short axis (S), shape index (S/L), echotexture, margins, ancillary features like calcification, necrosis, matting and surrounding tissue changes. These findings were correlated with fine-needle aspiration cytology, core and excisional biopsy. The nodes were classified as benign (reactive) and malignant (lymphomatous and metastatic).Results: The age of patients ranged from five to seventy five years, they were 45 male and 36 females, there was association between family history and development of malignant lesions. Regarding clinical evaluation, and according to consistency, (13) hard L.Ns were malignant and (1) was benign, (27) rubbery L.Ns were malignant and 40 soft L.Ns were benign. According to fixation to underlying structure, forty one L.Ns were fixed, (40) were malignant and (1) was benign. Forty L. Ns were not fixed, on histopathological evaluation all were benign. On US, the results showed that malignant lymph nodes are mostly appeared as round shape, homogenous echotexture, nodal shape (S/L ratio) accurate for differentiating benign from malignant lymph nodes. Most of the malignant nodes had well-defined borders. Calcifications, necrosis, matting, were characteristically found in benign lymph node. A combined ultrasound-guided and fine-needle aspiration (FNA) diagnosis had a high accuracy as compared with situations in which they were used alone.Conclusions: Sonographic findings have a high accuracy in differentiating benign from malignant cervical lymph nodes. An ultrasound scan can be used as the first-line imaging tool in the diagnostic evaluation of cervical lymphadenopathy. Using gray scale features are particularly useful to identify the causes of cervical lymphadenopathy.

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Article
Percutaneous Drainage of Abdominal Collections under Imaging Guide

Authors: Safa M. Al Obaidi صفاء العبيدي --- Mohammed A. Mahdi محمد عبد الامير مهدي --- Nasser M. Meazher ناصر مظلوم مزهر
Journal: Journal of the Faculty of Medicine مجلة كلية الطب ISSN: 00419419 Year: 2017 Volume: 59 Issue: 1 Pages: 5-8
Publisher: Baghdad University جامعة بغداد

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Abstract

Background: One of the most significant advances in the treatment of intra-abdominal collections during the past 2 decades has been the introduction of image-guided therapy with percutaneous catheter drainage. The development of improved imaging modalities, together with broad-spectrum antibiotics and soft drainage catheters, has changed the treatment of collections that previously required an urgent operation. Disease processes that have traditionally been treated with open surgical drainage and debridement can now be resolved with percutaneous catheter drainage and antibiotics. In selected cases, this will allow for better preparation of the patient for a later elective and definitive operation.Objective: Highlight the outcome, safety and effectiveness of percutaneous drainage procedure of abdominal collections performed under imaging guide.Patients and Methods: Forty one patients were referred from surgical wards and emergency department after diagnosing abdominal collections. Then each case discussed with radiologist to determine the route and type of catheter and imaging modality for guidance (ultrasound and/or computerized tomography). The size and site of the collections were estimated along with the most suitable approach and angle of catheter insertion. A safe drainage route was identified avoiding solid organs and bowel.Results: Percutaneous drainage of 41 abdominal collections under imaging control was carried out in 41 patients during a one year period. No complications resulted from the procedure itself. Percutaneous drainage was sufficient to drain the collections in 35 cases (no further surgery is needed). Of those who require surgery (5 patients), the procedure considered to be as a temporary measure. One case was diagnosed as sero-mucinous tumor of bowel.Conclusion: Percutaneous drainage of abdominal collections is a safe, effective and minimally invasive alternative approach to formal surgical drainage.The advantages include: the drainage can be done under local anesthesia, diagnosis and treatment can be achieved simultaneously in radiological department.Key words; Percutaneous drainage, Imaging guide, Collection.

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