Charakterizace tenkovrstvých elektroluminiscenčních součástek

Jádrem této disertační práce bylo studovat optické a elektrické charakteristiky tenkovrstvých elektroluminiscenčních součástek řízených střídavým proudem (ACTFEL) a zejména vliv procesu stárnutí luminiforů na jejich optické a elektrické vlastnosti. Cílem této studie měl být příspěvek ke zvýšení celkové účinnosti luminoforů, vyjádřené pomocí jasu, účinnosti a stability. Vzhledem k tomu, že současnou dominantní technologií plochých obrazovek je LCD, musí se další alternativní technologie plošných displejů porovnávat s LCD. Výhodou ACTFEL displejů proti LCD je lepší rozlišení, větší teplotní rozsah činnosti, větší čtecí úhel, či možnost čtení při mnohem vyšší intenzitě pozadí. Na druhou stranu je jejich nevýhodou vyšší energetická náročnost, problém s odpovídající barevností tří základních barev a podstatně vyšší napětí nutné pro činnost displeje. K dosažení tohoto cíle jsme provedli optická, elektrická a optoelektrická měření ACTFEL struktur a ZnS:Mn luminoforů. Navíc jsme studovali vliv dotování vrstvy pomocí KCl na chování mikrostruktury a na elektroluminiscenční vlastnosti (zejména na jas a světelnou účinnost) ZnS:Mn luminoforů. Provedli jsme i některá, ne zcela obvyklá, měření ACTFEL součástek. Vypočítali jsme i rozptylový poměr nabitých barevných center a simulovali transportní charakteristiky v ACTFEL součástkách. Studovali jsme vliv stárnutí dvou typů ZnS:Mn luminoforů (s vrstvou napařenou či získanou pomocí epitaxe atomových vrstev) monitorováním závislostí svítivost-napětí (L-V), velikost vnitřního náboje - elektrické pole luminoforu (Q-Fp) a kapacitance-napětí (C-V) ve zvolených časových intervalech v průběhu stárnutí. Provedli jsme krátkodobá i dlouhodobá měření a pokusili jsme se i o vizualizaci struktury luminoforu se subvlnovým rozlišením pomocí optického rastrovacího mikroskopu pracujícího v blízkém poli (SNOM). Na praktickém případu zeleného Zn2GeO4:Mn (2% Mn) ACTFEL displeje, pracujícího při 50 Hz, jsme také studovali stabilitu svítivosti pomocí měření závislosti svítivosti na napětí (L-V) a světelné účinnosti na napětí (eta-V). Přitom byl zhodnocen význam těchto charakteristik. Nezanedbatelnou a neoddělitelnou součástí této práce je i její pedagogický aspekt. Předložený text by mohl být využit i jako učebnice pro studenty na mé univerzitě v Lybii.The objective of this thesis is to study the optical and electrical characterization of Alternating-Current Thin-Film ElectroLuminescent (ACTFEL) devices, and specifically the aging process of phosphor materials that comprise the ACTFEL display in an effort to improve the overall performance of the primary phosphor colors in terms of brightness, efficiency and stability. Since the dominant flat-panel display technology is the LCD, an alternative flat-panel display technology must gauge itself in terms of the LCD. The advantages of ACTFEL displays in comparison with LCDs are the ability to pattern much smaller pixel, performance over a wider temperature range, full-viewing angle, and readability with much greater intensity background light. The disadvantages of ACTFEL displays against LCD ones are larger power consumption, lack of adequate chromaticity of the three primary colors, and much larger driving voltages. To achieve these objectives, the optical, electrical, and opto-electric measurements of the ACTFEL structures and ZnS:Mn phosphor hosts were carried out. Moreover, the effect of KCl co-doping on the microstructure and the electroluminescent properties (mainly brightness and luminous efficiency) of ZnS:Mn phosphors has been investigated, too. A non-common electrical characterization of ACTFEL devices has also been provided. We also calculated charged center scattering rates, and simulated the electron transport process in an ACTFEL device The study of the aging characteristics of evaporated and atomic layer epitaxy ZnS:Mn phosphors has been undertaken by monitoring the luminance-voltage (L-V) internal charge-phosphor field (Q-Fp) and capacitance-voltage (C-V) electrical characteristics at in selected time intervals during aging. Short-term and long-term ACTFEL aging studies has been provided and an attempt to visualize locally the structure of phosphor with a subwavelenght resolution using Scanning near-field optical microscope (SNOM) has also been presented. The practical case of a green Zn2GeO4:Mn (2% Mn) ACTFEL device operated at 50 Hz was studied and a luminance stability by a measurement of luminance-voltage (L-V) and luminous efficiency-voltage (eta-V) characteristics has been evaluated. A non-negligible and indiscreptible task of this thesis was also its pedagogical aspect. Therefore, the presented text can be considered as a textbook suitable for our students in Libya.

Participation as a complex phenomenon in the EFL classroom

PhD ThesisThe present study is concerned with the process of how EFL learners organise their classroom participation. Although oral engagement is considered the main indicator of student participation, opportunities to participate in oral discussion are not always available to all students due to different issues, (e.g., a large number of students in the class). The main focus of this research is therefore to describe how students participate in classroom discussion through other modes rather than explicit oral participation. This study involves the analysis of different forms of student participation used alternatively in EFL classrooms. Such forms related to the ongoing discussion are employed for different purposes by EFL students. Since previous studies have focused on verbal participation such the interrelated issues between teacher-student exchanges, much remains to be learned about the micro-interactional practice used by language learners to participate in classroom interaction. Therefore, this study aims to extend the existing knowledge of student participation in EFL classrooms. The analysis of data is based on Conversation Analysis (CA) methodology which can be used to analyse language and its environment, including a combination of talk and the use of body in the classroom context. The data base consists of about 14 hours of video and audio recorded lessons taken from second and third-year students of English Departments in Libyan universities. The reason for using video and audio recordings is that to have good chance for deep analysis of talk and embodied action. The findings show that there are other forms of student participation, including embodied action and desk talk. Embodied action analysis reveals that students as collaborative members rely on a variety of embodiments to sustain classroom interaction. The results obtained from this analysis provide evidence of the extent to which such these embodiments are exploited by language learners to participate in their classrooms. This means that students are not only orally participating but they are also non-orally constructing a kind of group participation through distributing meaningful signals. Such signals include different patterns of gazes, facial expressions, nodding heads body orientation and movements towards teacher or class. In addition, the findings show that desk talk produced beyond teacher-student talk is actually relating to the ongoing discussion. Students produce such desk talk in order to cope with ongoing discussion and to compensate for their lack of explicit oral opportunities to participate in classroom discussion

The role of soluble FMS-like tyrosine kinase (sFLT1) and FAS associated proteins in pregnancies complicated by preeclampsia and intrauterine growth restriction (IUGR).

PhDCurrent thinking suggests that preeclampsia is associated with activation of the maternal vascular endothelium in response to factors released from the placenta due to placental hypoxia. Failure of physiological modification of spiral arteries due to impaired trophoblast invasion results in a several-fold increase in the risk of developing pre-eclampsia and/or (IUGR). The defect behind impaired trophoblast invasion is not fully explained and the aetiological factor(s) linked with the development of pre-eclampsia, compared to normotensive IUGR, is not known. In this thesis, I examined placental and serum levels of fms-like tyrosine kinase I (sFltl) and placental growth factor (PIGF), as mediators of angiogenesis, and Fas and FasL, as mediators of apoptosis, in three groups; preeclampsia, normotensive IUGR and controls who had abnormal mid-trimester uterine artery Doppler. Uterine artery Doppler flows were examined in 553 women at 24 weeks. 97 of them had abnormal uterine artery Doppler flow and were enrolled in this study. 86 women were followed up; among them eight women developed preeclampsia and seven developed normotensive IUGR. Umbilical artery Doppler examination 24 hours before delivery in both groups, showed significantly lowered resistance indices in the preeclampsia compared to the normotensive IUGR group. I examined placental and serum levels of fms-like tyrosine kinase I (FIt I) and Placental Growth Factor (PIGF) in three groups. Soluble FItI acts as an antagonist for both Vascular Endothelial Growth Factor (VEGF) and PIGF. Placental FIt 1 and serum sFlt 1 were higher and serum PIGF was lower in the preeclampsia group compared to the other two groups. This could be responsible for the systemic manifestations of preeclampsia. This dysregulation in serum sFltl and PIGF was found as early as 24 weeks in pregnancies with abnormal uterine artery Doppler examination. The normotensive IUGR group had significantly elevated serum sFlU compared to controls. This could be due to an element of placental hypoxia in the IUGR group. To investigate the in-vivo effect of sFltl on impaired placental angiogenesis and trophoblast invasion, I examined the correlations between uterine artery Doppler resistance indices and serum sFIU and PIGF at 24 weeks. Significant correlations were found between these markers and uterine artery Doppler pulsatility index (pn and resistance index (Rn on both the placental and non-placental sides at 24 weeks. Fas and Fas ligand (FasL) are membrane proteins that mediate cellular apoptosis, and recently were related to cellular growth and migration. Using western blotting and immunohistochemistry, placental expression of Fas (western blotting) and (FasL) (immunohistochemistry) was assessed in the three study groups. No differences in placental Fas or Fas ligand were found between the groups. In addition, serum levels of Fas and FasL were measured at 24 weeks and within 24 hours of delivery in the same groups. Serum Fas was not different between the three study groups at 24 weeks and within 24 hours of delivery. Serum FasL was below the kit's detection threshold in the samples studied. In conclusion, placental FlU and its soluble form sFltl seem to play an important role in the pathophysiology of preeclampsia. In addition, sFltl correlated positively with the severity of impaired trophoblast invasion and could playa central role in blocking placental angiogenesis in these pregnancies. This needs further evaluation. Fas and FasL do not seem to have a role In impaired placentation and development of preeclampsia and IUGR

Enhancement Of Transmission Control Protocol Performance Over Low Earth Orbit Satellite Links

Recent growth of the Internet has led to the development of Internet services everywhere and over every possible communications medium. Here, Low Earth Orbit (LEO) Satellite has been addressed as a medium for supporting services based on the Transmission Control Protocol (TCP). Basically, TCP was proposed as a common transport protocol for the Internet. The TCP mechanisms have been modified overtime and almost standardized for wired networks. However, for wireless communications still further modifications are needed for TCP mechanisms. Particularly, in this study an Enhanced Selective Acknowledgement (ESACK) mechanism has been proposed to improve the performance of TCP over LEO satellite links. The ESACK detects the network congestion and adjusts the transmission window by considering losses in two consecutive windows

Collaborative Translational Research and Control of Meningitis in Sudan

Sudan lies within the meningitis belt and meningococcal disease has been one of its major problems throughout the twentieth century. Over 12,000 and 55,000 cases were recorded in the years 1935 and 1950 respectively; and during the period 1968-1980, over forty thousands (40,513) were inflicted with the disease of whom 1,220 have died. A collaborative translational research between the University of Khartoum and Uppsala University in Sweden managed to document the epidemiology, clinical features and complications of childhood acute bacterial meningitis (ABM) in Sudan during both an inter-epidemic (endemic) period (1985-1986), and the 1988 serogroup A epidemic; and to examine the phenotypic and genetic similarities and differences of Neisseria meningitidis strains isolated in Sudan and Sweden. A novel enzyme immunoassay test (Pharmacia Meningitis EIA-Test) was evaluated as a potential rapid diagnostic method for the detection of Haemophilus influenzae (HI) type b, Neisseria meningitidis (MC) and Streptococcus pneumoniae (PNC)

The Era of Pediatric Neurogenetics

Following the successful implementation of the Expanded Program on Immunization worldwide, and with the improvement in childhood nutrition, genetic diseases emerged as a significant health problem causing significant mortality and life-long morbidity. The majority of these genetic disorders manifest in childhood with either neurobehavioural impairment or as degenerative neurological disorders

Measuring the Impact of Schistosomiasis Infection on Different Blood Parameters

Background. Schistosoma is a genus of trematodes, Schistosoma spp., commonly known as blood-flukes and bilharzia, cause the most significant infection of humans by flatworms and are considered by the World Health Organization (WHO) as second in importance only to malaria. Objective of the study .This study was carried out in Sudan in the period from December 2009 to  February 2010 to assess effects Schistosomamansoni on hemoglobin (Hb) level, red blood cell count (RBCs count), total leucocyte count (TLC), paced cell volume (PCV), mean cell volume (MCV), mean cell hemoglobin (MCH), mean cell hemoglobin concentration (MCHC), and total platelet count . Study design .One hundred Schistosomamansoni infected patients included in this study ( 77 males , and 23 females).More fifty  samples were collected from normal persons and used as control. Density of parasitemia was calculated using Kato Katz technique. 5 ml venous anticoagulated blood were drawn from each participant . blood was analysed for aboved parameters using Mythic 18 cell counter. Results. the results showed that the means of different blood parameters were as followed : Hb:13 g/dl, PCV:40%, MCV:78 fl, RBC:5.2X 1012/L, MCH: 25pg, MCHC: 31g/dl, TLC: 7.4x109/L, and Total Platelet count:245x109/L in male group, and Hb: 12g/dl, PCV: 37%, MCV: 74 fl, TRBC: 5x1012/L, MCH: 23 fl, MCHC: 31g/dl, TLC: 6.7x109, and total platelet count: 240x109/L for female group. Conclusion. The study concluded that there a reduction in most parameters when compared to control group. Also this study reported a significant reverse association between density of parasitemia in all parameters except TLC and TRBC. Key words. Schistosoma mansoni, blood parameters, Halfa Aljadeeda town, Suda

Dietary assessment and nutrition pattern of maternal with gestation diabetes at Misurata Medical Centre

Background: The gestational diabetes mellitus (GDM) is yet another pregnancy complication for a pregnant woman, GDM happens when the body fails to produce enough insulin to regulate the sugar in blood. A healthy dietary regimen and eating behavior regarding GDM is a necessarily to ensure the health and development of pregnancy stages. Objectives: This study was conducted to assess nutrition patterns of gestation diabetes, also to correlate fasting blood glucose and HbA1c with anthropometric parameters, lifestyle and dietary pattern of maternal with GDM at Misurata. Materials and methods: Hospital-based cross section study was performed on 150 participants, whose selected randomly from Misurata Medical Centre (MMC). The data were collected thoroughly structured questionnaire and patient file. Result: The majority of participants (68 %) were fall with age group 20–35 years, greater of maternal at third trimester (55 %), maternal (22 %) had delivered babies with birth weight than 4 kg. Greater maternal (75 %) had family history with diabetes mellitus, whose diagnosed with polycystic ovary syndrome (19 %) and obesity (72 %) obese. The results revealed that majority of participant (84 %) hadn’t therapeutic diet. Highest rates of participants (57 %, 83 %, 80 %) had consumed high glycemic, fast and fatty food. Majority of participants (78 %) had elevated fasting blood glucose (≥120 mg/dl). Greater participants (92 %) had elevated HbA1c (≥6.5 %). Highly significant correlation (P≤0.01) of HbA1c and FBS with multi-pregnancies, age, birth weight and multiparty. Whereas, a significant correlation (P≤0.05) between weight birth, age, multi-pregnancy and abortion. Conclusion: the nutrition risks factors associated GDM will threatening health pregnancy unless the maternal committed with therapeutic diet pla

Assessment of Plasma Fibrinogen Level and Lipid Profile in Sudanese Smokers

Background: Cigarette smoking is a leading preventable risk factor for the development and progression of cardiovascular diseases (CVDs). Epidemiologic studies in smokers confirm the association between the alteration in lipid profile levels and CVDs risk. Fibrinogen, an acute phase reactant with active involvement in endothelial function, thrombosis and inflammation. It is signified as a systemic marker of carotidatherosclerosis. The purpose of this study was to assess the level of fibrinogen and lipid parameters in Sudanese tobacco smokers. Methods: This case-control study included 55 adult male of a current smoking status; their ages ranged between 18 and 54 years, and 100 non-smokers considered as controls. We evaluated the effect of cigarette smoking on plasma fibrinogen and serum lipid profile. The American Heart Association guidelines and reference ranges were used to identify the smokers with increased risk of coronary heart disease. Results: Our study revealed an increase in the levels of fibrinogen, total cholesterol, and low-density lipoprotein cholesterol (LDL-C) among smokers than controls, whereas the mean level of and triglycerides did not differ. The levels of highdensity lipoprotein cholesterol HDL-C demonstrated decrement. Further, smokers were classified according to the atherogenic risk index LDL-C/HDL-C ratio, the studied parameters fibrinogen, total cholesterol, and triglycerides were significantly increased in those who have ratio 4.5 and more (p = 0.001, p = 0.018, p = 0.007, respectively). Smokers with atherogenic index ≥ 4.5 were more likely to have ≥ 300 mg/dl fibrinogen level (odds ratio (OR) 3.96, 95% confidence interval (95%CI) 1.14– 13.73, p = 0.026). Moreover, the level of the fibrinogen can be predicted by linear regression equation: Fibrinogen level = 19.49 + 79.08 (the ratio of LDL-C ⁄HDL-C), r = 0.37, p = 0.008, 95%CI 21.20–136.95. Conclusion: Increased fibrinogen, LDL-C, and LDLC/HDL-C ratio may potentiate the development of cardiovascular disease in smokers