High Power Gain Guided Index Antiguided Fiber Lasers and Amplifiers

Abstract Increasing the core size of high-power fiber lasers and amplifiers is highly desired in order to mitigate the unwanted nonlinear optical effects and raise the optical damage threshold. If the core size of conventional index-guided (IG) optical fibers increases, the fiber will become multimode, because it is very difficult to control and fine-tune the index step between the core and cladding to satisfy the single mode condition. Siegman proposed Gain-guided index-antiguided (GG-IAG) fibers as a possible platform for ultra-large-core single-mode operation for lasers and amplifiers. In this thesis, the beam-quality factor M2 for the fundamental LP01 mode of a step-index fiber with finite and infinite cladding diameter is calculated in the presence of gain as a function of the complex generalized V number. The numerical results agree with analytical work that obtained in our group. It is shown that the M2 value of a single-mode gain-guided fiber laser can be arbitrarily large. The results are important for the interpretation of the beam-quality measurements in recent experiments on single-mode gain-guided fiber lasers. It is also shown that the conventional infinite cladding diameter approximation cannot be used for index-antiguided gain-guided fibers, and the rigorous analysis is required for accurate prediction of the beam quality factor, as reported in recent experimental measurements. We also highlight the key reasons behind the poor power efficiency observed in multiple experiments in gain guided index-antiguided (GG-IAG) fiber amplifiers and lasers. We show that by properly designing the fiber geometrical characteristics, it is possible to considerably improve the power efficiency of GG-IAG fiber amplifiers in end-pumping schemes

Semantic Rule-based Approach for Supporting Personalised Adaptive E-Learning

Instructional designers are under increasing pressure to enhance the pedagogical quality and technical richness of their learning content offerings, while the task of authoring for such complex educational frameworks is expensive and time consuming. Personalisation and reusability of learning contents are two main factors which can be used to enhance the pedagogical impact of e-learning experiences while also optimising resources, such as the overall cost and time of designing materials for different e-learning systems. However, personalisation services require continuous fine tuning for the different features that should be used, and e-learning systems need sufficient flexibility to offer these continuously required changes. The semantic modelling of adaptable learning components can highly influence the personalisation of the learning experience and enables the reusability, adaptability and maintainability of these components. Through the discrete modelling of these components, the flexibility and extensibility of e-learning systems will be improved as learning contents can be separated from the adaptation logic which results in the learning content being no longer specific to any given adaptation rule, or instructional plan. This thesis proposes an innovative semantic rule-based approach to dynamically generate personalised learning content utilising reusable pieces of learning content. It describes an ontology-based engine that composes, at runtime, adapted learning experiences according to learner’s interaction with the system and learner’s characteristics. Additionally, enriching ontologies with semantic rules increases the reasoning power and helps to represent adaptation decisions. This novel approach aims to improve flexibility, extensibility and reusability of systems, while offering a pedagogically effective and satisfactory learning experience for learners. This thesis offers the theoretical models, design and implementation of an adaptive e-learning system in accordance with this approach. It also describes the evaluation of developed personalised adaptive e-learning system (Rule-PAdel) from pedagogical and technical perspectives

On the Beam Profile and Beam Quality of Gain-Guided Index-Antiguided Fibers with Finite Cladding Boundary

The beam quality factor $M^2$ for the fundamental LP01 mode of a step-index fiber with a finite cladding diameter is calculated in the presence of gain, in a closed form, as a function of the complex generalized V-number. It is shown that the conventional infinite cladding diameter approximation cannot be used for index-antiguided gain-guided fibers, and the rigorous analysis presented in this paper is required for accurate prediction of the beam quality factor, as reported in recent experimental measurements

Accuracy of Visual inspection with acetic acid (VIA) for early detection of cervical dysplasia in Tehran, Iran

Objective: To evaluate the accuracy of visual inspection with 5 acetic acid (VIA) when used to detect cervical cancer and its precursors. Methods: The study population included women attended Family Planning and Gynecological Clinic in Bagher Abad Health Center and Mirza Koochak Khan Hospital for regular cervical screening tests. After obtaining informed consent from each woman, VIA was performed. One hundred with a positive VIA test and 100 women with a negative VIA test were randomly selected for this study. Cytology and colposcopy examination were performed for all 200 cases and cervical biopsies were conducted for those individuals showing abnormal colposcopic findings. Results: Nine cases in VIA-positive group and two cases in VIA-negative group had an abnormal cytology. Ninety five women in the VIA-positive group and 25 in the VIA-negative group had abnormal colposcopic findings. From biopsy examination, 67 (71) of cases in the VIA-positive group and 3 (12) cases in the VIA-negative group had a final diagnosis of dysplasia. Among biopsied samples, only 7 cases of VIA-positive group showed abnormal result and the remaining were normal. Based on these results, VIA test sensitivity and specificity were 95.7 and 44.0 respectively, while they were 10 and 92 for cytology tests. Conclusions: The results of this study indicate that although VIA is a sensitive screening test for detection of cervical dysplasia, it can not be used by itself. Applying VIA along with Pap smears helps to detect a higher number of cases with cancer precursor lesions

Prevalence of human papillomavirus genotypes in women with normal and abnormal cervical cytology in Iran

Introduction: HPV infection has a prime etiologic role in development and progression of cervical cancer, one of the most frequent forms of cancer among women in developing countries. This study was designed to determine the most prevalent HPV genotypes in women with normal and abnormal cervical cytology in Iran. Materials and Methods: Samples from134 patients, including 127 who attended gynecology clinics and 7 with solid cervical tumors were used. All 127 patients underwent routine Pap tests for cytological evaluation and at the same visit a sample of cervical epithelial cells was obtained by scraping the cervix osteum. In each case HPV infection was primarily evaluated by PCR using GP 5/6 primers and then subtyping was performed in proved infected samples with specific primers for HPV 16, 18, 31, 33, 11 and 6. After cytological evaluation, 50 patients with abnormal Pap tests were categorized as the abnormal group and the remaining 77 patients as the normal group. Results: In the normal group, HPV infection was established in 10 cases (13% infection rate), while 30 HPV positive cases were discovered in the abnormal group (60% infected). The most prevalent genotypes among the infected samples were HPV 16 (76%), HPV18 (12.7%) and HPV11/6 (8.5%). Moreover, all 7 tumor samples were positive for HPV general primers of which, 5 samples were infected with HPV 16, two were co-infected with HPV16,18 and HPV16,31 genotypes and one was infected with HPV 18. Conclusions: Infection with HPV 16 was found to be significantly higher in abnormal group in comparison with normal group (42% vs. 11.6%, P value <0.005), likewise HPV18 genotypes were proved to be more prevalent in abnormal group (8% vs. 0%, P value <0.05). No significant relation between other HPV genotypes and pathologic cervical changes was obtained. According to our study high rates of infection with HPV genotypes in sexually active Iranian women makes molecular investigation for HPV16 and 18 very essential in clinical approaches to patients with proven dysplasia in their screening tests and also for those patients with borderline (i.e. ASCUS) or incongruous pathology reports. Larger studies are required to determine the most appropriate vaccine with highest protection in Iranian women

Comparison of EMLA and Diclofenac on Reduction of Pain and Phlebitis Caused by Peripheral IV Catheter: A Randomized-Controlled Trial Study

Peripheral venous catheters (PVC) are often used to provide hydration, medications, and blood products when the length of therapy is expected to be less that one week. Pain and phlebitis are frequent complications of PVC. Diclofenac and EMLA have been used to minimize these adverse effects, however, conflicting results have been reported regarding which has better outcomes. This double-blind, randomized controlled trial was conducted to compare the efficacy of EMLA and Diclofenac (TDP) in attenuating PVC pain and phlebitis. The inpatient setting was chosen because of the higher frequency of PVC insertions, allowing for a sufficient sample size. One hundred fifty-four subjects were randomly assigned to three groups: EMLA patch, a TDP patch, or a patch with lubricant gel as a placebo. The pain was measured by Visual Analogue Scale (VAS). Phlebitis was examined based on Boxter criteria in intervals of 6, 12, 18, 24, and 48 hours after PVC insertion. The mean score of VAS was 41.86 ± 22.49 for the control, 39.40±21. 60 for TDP, and 38.77± 23.28 for the EMLA group, with no significant differences in pain severity between the three groups. The rate of phlebitis in the group with EMLA was significantly higher than the other two groups at 6,12, and 18 hours (p=0.02, p= 0.003 and p=0.04, respectively). In all interval times, the rate of phlebitis in the TDP group was significantly lower than the other groups. Compared to men, women experienced higher rate of phlebitis and intensity of PVC pain. EMLA and TDP had similar analgesic effects, but phlebitis was less frequently observed with TDP, suggesting TDP as a potential medication for reducing pain and phlebitis before PVC insertion

Empirical developments in retraction

This study provides current data on key questions about retraction of scientific articles. Findings confirm that the rate of retractions remains low but is increasing. The most commonly cited reason for retraction was research error or inability to reproduce results; the rate from research misconduct is an underestimate, since some retractions necessitated by research misconduct were reported as being due to inability to reproduce. Retraction by parties other than authors is increasing, especially for research misconduct. Although retractions are on average occurring sooner after publication than in the past, citation analysis shows that they are not being recognised by subsequent users of the work. Findings suggest that editors and institutional officials are taking more responsibility for correcting the scientific record but that reasons published in the retraction notice are not always reliable. More aggressive means of notification to the scientific community appear to be necessary

Metformin therapy before conception versus throughout the pregnancy and risk of gestational diabetes mellitus in women with polycystic ovary syndrome : a systemic review, meta-analysis and meta-regression

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Malignant mixed mullerian tumor of the uterus associated with tamoxifen therapy in a patient with a history of breast cancer

Tamoxifen is the drug of choice in the treatment of breast cancer. Recent reports show an increased incidence of endometrial carcinoma in patients taking tamoxifen. In this article, we report a case of malignant mixed mullerian tumor after tamoxifen use. Copyright © 2006 by Razi Institute for Drug Research (RIDR)

A personalized adaptive e-learning approach based on semantic web technology

Recent developments in semantic web technologies heightened the need for online adaptive learning environment. Adaptive learning is an important research topic in the field of web-based systems as there are no fixed learning paths which are appropriate for all learners. However, most studies in this field have only focused on learning styles and habits of learners. Far too little attention has been paid on understanding the ability of learners. Therefore, it is becoming increasingly difficult to ignore adaptation in the field of e-learning systems. Many researchers are adopting semantic web technologies to find new ways for designing adaptive learning systems based on describing knowledge using ontological models. Ontologies have the potential to design content and learner models required to create adaptive e-learning systems based on various characteristics of learners. The aim of this paper is to present an ontology-based approach to develop adaptive e-learning system based on the design of semantic content, learner and domain models to tailor the teaching process for individual learner’s needs. The proposed new adaptive e-learning has the ability to support personalization based on learner’s ability, learning style, preferences and levels of knowledge. In our approach the ontological user profile is updated based on achieved learner’s abilities