Light effect in photoionization of traps in GaN MESFETs

Trapping of hot electron behavior by trap centers located in buffer layer of a wurtzite phase GaN MESFET has been simulated using an ensemble Monte Carlo simulation. The results of the simulation show that the trap centers are responsible for current collapse in GaN MESFET at low temperatures. These electrical traps degrade the performance of the device at low temperature. On the opposite, a light-induced increase in the trap-limited drain current, results from the photoionization of trapped carriers and their return to the channel under the influence of the built in electric field associated with the trapped charge distribution. The simulated device geometries and doping are matched to the nominal parameters described for the experimental structures as closely as possible, and the predicted drain current and other electrical characteristics for the simulated device including trapping center effects show close agreement with the available experimental data.Comment: 5 pages, 2 figure

Static Characterization of InAs/AlGaAs Broadband Self-Assembled Quantum Dot Lasers

The static-characteristics of InAs/AlGaAs broadband self-assembled quantum-dot laser diodes (SAQD-LDs) have been studied to solve the rate equations numerically using fourth-order Runge-Kutta method. Energy level, size, and composition distributions of the InAs/AlGaAs broadband quantum-dots (QDs) are considered and their effects on Static-characteristics are investigated. Simulated results of static-characteristics show that nonlinearity appears in light-current characteristics whereas homogeneous broadening (HB) becomes equal to inhomogeneous broadening (IHB). Slope-efficiency increases as the HB heightens up to the IHB. Exceeding the HB from IHB results in degradation of light-current characteristics. In fact, InAs/AlGaAs broadband SAQD-LD has the best performance when HB is equal to IHB. Light-current characteristics degrade and threshold current increases as the IHB enhances. We also investigate the effects of QD coverage on the laser performance and show that there is an optimum QD coverage in which the SAQD-LD operates with lowest possible threshold current and maximum output power as whatever the QD coverage enhances from that optimum amount, the threshold current increases and slope efficiency decreases. 

Two Dimensional Coulomb Potential of Confined Excitons in Quantum Well Structures

In this study, we have investigated an exciton confined in a single quantum well. For the first time, we have compared the different methods of approximating the effective two dimensional Coulomb potentials which had been previously reported in the literatures. The effect of different previously introduced trial wave functions on the exciton binding energy is also investigated. In order to have a consistent and stable calculation we have tried to find the true region of variations for free parameters of these trial wave functions. Effects of the barrier thickness and doping fraction are also investigated. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3026

The effect of magnetic water on strength parameters of concrete

A machine for magnetic water treatment is designed and its application on the ions contained in water has been investigated to examine the effect of magnetic water on concrete parameters. Strength parameters of concrete have been studied for more than 104 concrete samples, including the nonmagnetic samples (made by ordinary water) and magnetic samples (made by magnetic water), with slump and compressive strength experiments. Based on slump experiments, magnetic samples were 7 centimeters more than non-magnetic group and the average compressive strength of samples made by magnetic water was 23% more than that of samples made by ordinary water. The experimental results show the advantages of magnetic samples in concrete industry because of increase in plasticity, the efficiency and quality of concrete boosts in comparison with nonmagnetic samples

Scabies presenting with bullous pemphigoid-like lesions

A wide range of clinical manifestations may be seen in scabies, from classic pruritic papules and burrows to secondary features such as impetigo. Bullus lesions are a less frequent. Twenty cases of scabies presenting with bullae have been reported so far in the medical literature. Differentiating this subtype of scabies from the immunobullous disease bullus pemphigoid is a diagnostic challenge. A 42-year-old man was referred to our dermatology outpatient clinic with 3-month history of severe pruritus and tense blisters affecting mainly the lower trunk, arms and legs. An initial biopsy was suggestive for bullous pemphigoid. Close physical examination revealed small excoriated papules and a few burrows on borders of the hands and wrists. Skin scraping of the lesions on wrists was positive for Sarcoptes scabiei. Another biopsy specimen from a recent blister revealed subepidermal bullae with fibrin and inflammatory cells, particularly eosinophils. Direct immunofluorescence exam was negative. The patient was treated with lindane lotion followed by crotamiton cream with near complete resolution of the lesions. Scabies must be considered in patients presenting with recent onset of unexplained pruritic bullous lesions. Biopsy and immunofluorescence studies together with skin scrapings for Sarcoptes scabiei could help to differentiate these cases from bullous pemphigoid. Antiscabietic treatment results in resolution of bullous lesions in the affected patients. © 2006 Dermatology Online Journal

Clinical presentation and etiologic factors of hirsutism in premenopausal Iranian women

Background: Hirsutism is a common clinical condition with different etiologies. Many of these patients have frank or subclinical abnormalities in the adrenal and ovarian steroidogenesis. The disease may be associated with other clinical signs of hyperandrogenism. The objective of this study was to investigate the clinical features of hirsutism and its etiologic factors in premenopausal Iranian women. Methods: In a cross-sectional study, 790 consecutive premenopausal women referred to the dermatology Clinics of Hazrat-e Rasool and Firoozgar University Hospitals and three private dermatology clinics during 2001-2003 with the clinical diagnosis of hirsutism were studied. All patients underwent detailed clinical assessment and transabdominal ultrasonography of the ovaries. Endocrinologic work-up was performed for 285 patients. Results: Hirsutism was mild in 65, moderate in 32.5, and severe in 2.5 of the patients. Positive family history was found in 56.2. Hormonal studies revealed some abnormalities in 35.2 of the patients. Coexisting medical conditions included acne in 70 of the patients, menstrual irregularity in 38.6, androgenic alopecia in 21.3, obesity in 6.5, acanthosis nigricans in 4.9, and diabetes in 0.6 of the patients. Etiology of hirsutism was identified as polycystic ovary syndrome (62.53), idiopathic (35.19), congenital adrenal hyperplasia (0.38), prolactinoma (0.13), and undetermined (1.77). Polycystic ovary syndrome was diagnosed more frequently in women with menstrual irregularity than eumenorrheic patients (97.70 vs. 40.41, P < 0.001). Conclusion: Hirsute patients frequently have either elevated androgen levels or clinical conditions associated with hyperandrogenemia. Eumenorrhea does not rule out endocrine abnormality and particularly polycystic ovary syndrome which is a common cause of hirsutism. We recommend performing endocrinologic work up, investigation of coexisting hyperandrogenic. states, and evaluation of polycystic ovary syndrome in all patients with hirsutism

An early Little Ice Age brackish water invasion along the south coast of the Caspian Sea (sediment of Langarud wetland) and its wider impacts on environment and people

Caspian Sea level has undergone significant changes through time with major impacts not only on the surrounding coasts, but also offshore. This study reports a brackish water invasion on the southern coast of the Caspian Sea constructed from a multi-proxy analysis of sediment retrieved from the Langarud wetland. The ground surface level of wetland is >6 m higher than the current Caspian Sea level (at -27.41 m in 2014) and located >11 km far from the coast. A sequence covering the last millennium was dated by three radiocarbon dates. The results from this new study suggest that Caspian Sea level rose up to at least -21.44 m (i.e. >6 m above the present water level) during the early Little Ice Age. Although previous studies in the southern coast of the Caspian Sea have detected a high-stand during the Little Ice Age period, this study presents the first evidence that this high-stand reached so far inland and at such a high altitude. Moreover, it confirms one of the very few earlier estimates of a high-stand at -21 m for the second half of the 14th century. The effects of this large-scale brackish water invasion on soil properties would have caused severe disruption to regional agriculture, thereby destabilizing local dynasties and facilitating a rapid Turko-Mongol expansion of Tamerlane’s armies from the east.N Ghasemi (INIOAS), V Jahani (Gilan Province Cultural Heritage and Tourism Organisation) and A Naqinezhad (University of Mazandaran), INQUA QuickLakeH project (no. 1227) and to the European project Marie Curie, CLIMSEAS-PIRSES-GA-2009-24751

Visualization of clinical teaching citations using social network analysis

Background: Analyzing the previous research literature in the field of clinical teaching has potential to show the trend and future direction of this field. This study aimed to visualize the co-authorship networks and scientific map of research outputs of clinical teaching and medical education by Social Network Analysis (SNA). Methods: We Identified 1229 publications on clinical teaching through a systematic search strategy in the Scopus (Elsevier), Web of Science (Clarivate Analytics) and Medline (NCBI/NLM) through PubMed from the year 1980 to 2018.The Ravar PreMap, Netdraw, UCINet and VOSviewer software were used for data visualization and analysis. Results: Based on the findings of study the network of clinical teaching was weak in term of cohesion and the density in the co-authorship networks of authors (clustering coefficient (CC): 0.749, density: 0.0238) and collaboration of countries (CC: 0.655, density: 0.176). In regard to centrality measures; the most influential authors in the co-authorship network was Rosenbaum ME, from the USA (0.048). More, the USA, the UK, Canada, Australia and the Netherlands have central role in collaboration countries network and has the vertex co-authorship with other that participated in publishing articles in clinical teaching. Analysis of background and affiliation of authors showed that co-authorship between clinical researchers in medicine filed is weak. Nineteen subject clusters were identified in the clinical teaching research network, seven of which were related to the expected competencies of clinical teaching and three related to clinical teaching skills. Conclusions: In order to improve the cohesion of the authorship network of clinical teaching, it is essential to improve research collaboration and co-authorship between new researchers and those who have better closeness or geodisk path with others, especially those with the clinical background. To reach to a dense and powerful topology in the knowledge network of this field encouraging policies to be made for international and national collaboration between clinicians and clinical teaching specialists. In addition, humanitarian and clinical reasoning need to be considered in clinical teaching as of new direction in the field from thematic aspects. © 2021, The Author(s)

A qualitative approach to identify barriers to multi-professional teamwork among medical professors at Iranian teaching hospitals

Background: In some cases of diseases, such as infectious, neurological and chronic ones prevention and treatment is complex. Therefore, a single medical specialty alone cannot effectively manage treatment of patients due to health care needs of them and complexities of treatment. Instead, a team composed of different healthcare disciplines with effective, continuous, and organized communication must follow up various aspects of patient care. In this regard, the present qualitative study aimed to shed light on the experiences of clinical teachers of multi-professional teamwork barriers within Iranian teaching hospitals. Methods: In this qualitative research, the experiences of medical clinical teachers of multi-professional teamwork barriers within teaching hospitals were explained. Sampling was theoretical and the data were collected from experienced clinical teachers and medical students studying at several Universities of Medical Sciences through semi-structured interviews and observation, which were continued until data saturation. Fifteen clinical teachers and five medical students participated in the study. The interviews were analyzed using conventional content analysis. Results: Three main categories were extracted. The first category was �enhancing the culture of interdisciplinary education� included �paving the way for an interdisciplinary culture�, �enhancing teamwork culture�, and �having a general view of medical sciences instead of specialization�. The second category was �barriers of interdisciplinary education� included �influence of the dominant culture of specialization in society�, �poor interdisciplinary education infrastructure�, and �individualism as a value of society�. And the third category was �consequences of specialization� included �medical sciences education under the shadow of specialization�, �possibility to harming patients�, and �distrust of society in the services provided by the 1st and 2nd level centers�. Conclusion: It seems that attitudinal barriers, teamwork difficulties, and the culture of individualism are evident in Iran; more, roles of the healthcare team and the status of each member is not clear. Designing interactive curriculum and arranging clinical settings to facilitate exchange of ideas among clinical teachers and students of different disciplines, is a step forward to achieving a common value concept, language, and common perception, and establishing cooperation and understanding among disciplines involved, which leads to further understanding of the professional responsibilities of other disciplines. © 2021, The Author(s)

Humanism in clinical education: a mixed methods study on the experiences of clinical instructors in Iran

BACKGROUND: Medical education is currently more considerate about the human dimension. The present qualitative study aimed to explain the experiences of clinical professors with regard to humanism in clinical education in Iran. METHODS: This mixed methods study had two phases, a quanitative phase of scientometrics and a qualitative phase of a content analysis. In the scientometrics phase, Ravar PreMap and VOSviewer software programs were utilized for plotting the conceptual networks. The networks were analyzed at the micro-level based on centrality indices (closeness, degree, and betweenness). The conceptual network was plotted and the prominent topics in clinical education were identified using co-word analysis. In the second qualitative phase on the topic, based on the scientometrics phase, semi-structured interviews were conducted with clinical professors. The interviews were transcribed verbatim and analyzed. RESULTS: On the basis of the analysis of titles, abstracts, and keywords of the retrieved articles on clinical education from ISI Web of Science, Scopus, and PubMed, 1412 keywords were extracted. After the refining process, 356 keywords with 6741 relations remained. Upon plotting the conceptual network, 19 conceptual clusters related to clinical education were obtained. Then, micro-level network analysis (centrality criteria) indicated that the keyword humanism with the frequency of 137 had the highest rate (97.753), closeness (97.802), and betweenness (13.407). Moreover, from the interview data analysis, two themes of "intertwined nature of the human spirit in clinical education" and "humanistic behavior of professors in clinical education" were extracted. CONCLUSION: As a part of the educational culture, humanistic values must be intertwined with the medical education curriculum. In this regard, humanism and clinical reasoning are the two major clusters of clinical teaching; moreover, altruism and adherence to humanistic values, and scientific qualification are other main pillars that should be considered as the criteria for the selection of clinical professors and medical students