1,055 research outputs found

    Group velocity control in the ultraviolet domain via interacting dark-state resonances

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    The propagation of a weak probe field in a laser-driven four-level atomic system is investigated. We choose mercury as our model system, where the probe transition is in the ultraviolet region. A high-resolution peak appears in the optical spectra due to the presence of interacting dark resonances. We show that this narrow peak leads to superluminal light propagation with strong absorption, and thus by itself is only of limited interest. But if in addition a weak incoherent pump field is applied to the probe transition, then the peak structure can be changed such that both sub- and superluminal light propagation or a negative group velocity can be achieved without absorption, controlled by the incoherent pumping strength

    Design an optimized model to improve natural ventilation thorough the roof orientation

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    Natural ventilation is among those effective methods that is useful in hot dry climates. One of its important uses is in the atrium spaces in the office buildings. Although, as a passive solution, it has a significant impact on the reduction of energy consumption, the control of inlet and outflow of air as well as the control of air current temperature has always been a challenge for architects and engineers. This study aims at designing a model to reduce energy consumption and increase airflow inside the atrium. In so doing, the present study reviews the existing solutions in the inactive area. In this way, using computer simulations, the designed model in the energy software is analyzed and compared. The Design Builder Software is used to analyze the natural ventilation inside the building. The results clearly show that the use of a suitable form in the atrium ceilings with the aim of increasing the absorption of direct sunlight can have a direct effect on natural ventilation and thus reduce energy consumption in hot dry areas

    Isolation and typing of the influenza viruses in the Caspian littoral of Iran

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    Present study introduces results of common influenza virus strains in the north of Iran. Samples collected from 65 patients with acute respiratory illness by throat washing and swabs, randomly from north of Iran (Mazandaran, Golestan and Guilan provinces). The patients suffered from fever (high), cough, sore throat, general malaise, chill and myalgia. Viruses were isolated by cell culture and confirmed with HA (Hemagglutination) test and then typed by and HI (Hemagglutination Inhibition) test. Out of 65 throat samples, 12 influenza viruses were isolated and typed. Isolated viruses belonged to A (H1N1), A (H3N2) and B influenza viruses. This study showed that Influenza viruses displayed identical pattern to other provinces in Iran and to other countries. To fight against epidemics and pandemics, we should collect enough data about status of influenza each year and data of exact vaccine formulation application for use in different areas of the world. Acquired data has shown that the vaccine for above viruses that confirmed by WHO can result in decreased risks of influenza in at risk cases in provinces of north Iran

    The Farsi Version of the Strength and Difficulties Questionnaire Self Report Form: The Normative Data and Scale Properties

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     Objective:This study was performed to evaluate the normative data and psychometric properties and the internal consistency of the Farsi (Persian) version of the Strength and Difficulties Questionnaire (SDQ) self-report form, as a screening tool in a community-based sample of 12 to 17 year-old   adolescents of urban Tehran.Materials & Methods: In this investigation, 1105 adolescents (12 to 17 years old), selected from 250 clusters from all the 22 municipality areas of Tehran, responded to 25 questions of the Farsi version of SDQ self-report form. The frequency of each symptom domains according to Goodman's cutoff points and 90th percentile and the mean score in each subscale were determined.Results:The 90th percentile cutoff points were somewhat different from those of the previous reports. Using Goodman's cutoff points, the prevalence of symptom domains was relatively high. For example, 13.7 percent of the adolescents studied had total scores equal to 20 or more. There were significant  correlations between different subscales and their constituting questions.Conclusion:Self-report form of SDQ is a valuable tool in the screening of adolescent psychopathologies. Frequency of majority of the symptom domains seems to be higher in the adolescents in Tehran urban areas

    Light propagation through closed-loop atomic media beyond the multiphoton resonance condition

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    The light propagation of a probe field pulse in a four-level double-lambda type system driven by laser fields that form a closed interaction loop is studied. Due to the finite frequency width of the probe pulse, a time-independent analysis relying on the multiphoton resonance assumption is insufficient. Thus we apply a Floquet decomposition of the equations of motion to solve the time-dependent problem beyond the multiphoton resonance condition. We find that the various Floquet components can be interpreted in terms of different scattering processes, and that the medium response oscillating in phase with the probe field in general is not phase-dependent. The phase dependence arises from a scattering of the coupling fields into the probe field mode at a frequency which in general differs from the probe field frequency. We thus conclude that in particular for short pulses with a large frequency width, inducing a closed loop interaction contour may not be advantageous, since otherwise the phase-dependent medium response may lead to a distortion of the pulse shape. Finally, using our time-dependent analysis, we demonstrate that both the closed-loop and the non-closed loop configuration allow for sub- and superluminal light propagation with small absorption or even gain. Further, we identify one of the coupling field Rabi frequencies as a control parameter that allows to conveniently switch between sub- and superluminal light propagation.Comment: 10 pages, 8 figure

    Coping styles with stress in nursing and midwifery students

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    In the present year, attention has been paid to the nursing and midwifery students, especially when it comes to stress and coping strategies. Understanding the coping styles offered by students enables college officials to become aware of the needs of their pupils, the guidelines, and the training of their counterparts. This study aimed to systematically review on coping with stress in nursing and midwifery students was done. Data searches were conducted using stress keywords, coping styles, and nursing and midwifery students. The sites under study were database of Iranian Medical Sciences Articles (IranMedex), Scientific Database (SID) Pub Med, Mag Iran,, Scopus. The search of the above mentioned database was carried out from July to September 2019.Nineteen studies were studied with the aim of investigating the relationship between stress and aggression in nursing and midwifery students. Finally, the types of coping styles in nursing and midwifery students were examined in three areas of problem-centered, emotion-focused and avoidant. In general, the use of emotion-focused styles was more than problem-focused responses, while the use of such styles had a transient role in reducing stress. Therefore, it is suggested that educational managers and planners consider promoting problem-focused coping skills in students

    Staphylococcus aureus infections in children in an Iranian referral pediatric Hospital

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    Introduction. Staphylococcus aureus is associated with various infections ranging from skin and soft tissues such as surgical site infections and abscesses to lower respiratory tracts and blood- stream. The aim of this study was to evaluate underlying condi- tion of patients with S. aureus infections in an Iranian referral pediatric Hospital. Material and methods. Information was extracted retrospec- tively from the medical records of patients who were diagnosed with S. aureus infections. Data obtained about the study subjects included basic demographics, reason for admission, culture site, length of hospital stay, and methicillin susceptibility. Results. The underlyning condition of of patients with S.aureus infection during November 2011 and March 2013 were included in the study. The most frequent diagnosis in patients with S. aureus infection was jaundice (12%), abscess (10%), cellulitis (10%), wound infection (8%), septic arthritis (7%) and sezeire (5%). Wound was the most common infection sites among all subjects 34/98 (35%) following by blood (20/98, 20%) as well as skin and soft tissue (19/98, 19%). The proportion of MRSA infections among all S. aureus isolates was 79% (77/98) during the study period. In addition, 58/74 (78%) met the definition of Hospital-Associated Methicillin-Resistant S. aureus (HA- MRSA) infections and the rest; 20/24 patients (83%), were classified as Community-Associated Methicillin-Resistant S. aureus (CA- MRSA). Conclusion. In our study, the high frequency of MRSA was found not only in HA S. aureus but also in CA S. aureus isolates; there- fore, the strategic goals to optimize antimicrobial use includin
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