114 research outputs found
Frequency-Doubling of Femtosecond Pulses in “Thick” Nonlinear Crystals With Different Temporal and Spatial Walk-Off Parameters
We present a comparative study on frequency-doubling characteristics of femtosecond
laser pulses in thick nonlinear crystals with different temporal and spatial walk-off
parameters. Using single-pass second harmonic generation (SHG) of 260 fs pulses at
1064 nm from a high-average-power femtosecond Yb-fiber laser in 5-mm-long crystals of
β-BaB2O4 (BBO) and BiB3O6 (BIBO), we find that for comparable values of temporal and
spatial walk-off parameters in each crystal, the optimum focusing condition for SHG is more
strongly influenced by spatial walk-off than temporal walk-off. It is also observed that under
such conditions, the Boyd and Kleinman theory commonly used to define the optimum focusing
condition for frequency-doubling of cw and long-pulse lasers is also valid for SHG
of ultrafast lasers. We also investigate the effect of focusing on the spectral, temporal, and
spatial characteristics of the second harmonic (SH) radiation, as well as angular acceptance
bandwidth for the SHG process, under different temporal and spatial walk-off conditions in
the two crystalsPeer ReviewedPostprint (author's final draft
Model Development of Afterschool Programs in Cyberspace for Third grade Students of Guidance School
This research studies the design of a model of afterschool programs in cyberspace for third grade students of guidance school in 2012-2013 school year in Tehran City. For this purpose, the main parameters of the model were identified and their interrelations were studied, in order to identify the determining needs and major parameters of afterschool programs in cyberspace. A researcher-made questionnaire has been used for the students and a semi-structured interview for the principals, teachers and other educational staff. The data collected from the questionnaires and the interviews were processed and analyzed by SPSS and AMOS. Thus the conceptual model "after school programs in cyberspace " was confirmed. According to the needs analysis that was performed, the parameters of the after school programs in cyberspace were divided into two exogenous parameters of knowledge and skill and seven endogenous parameters of individual-social features, gaining knowledge extracurricular use, accessibility to information and sources, leisure, place of after school programs, and network features. Finally, the results indicated that the two parameters of individual –social features and place of after school programs in having the most direct and indirect effects on the model of after school programs in cyberspace. Further, in addition to identifying the major parameters of afterschool programs and studying the amount of effects of each of them. The causes and necessity of such programs were studied according to the qualitative and quantitative results
Temperature-dependent proximity magnetism in Pt
We experimentally demonstrate the existence of magnetic coupling between two
ferromagnets separated by a thin Pt layer. The coupling remains ferromagnetic
regardless of the Pt thickness, and exhibits a significant dependence on
temperature. Therefore, it cannot be explained by the established mechanisms of
magnetic coupling across nonmagnetic spacers. We show that the experimental
results are consistent with the presence of magnetism induced in Pt in
proximity to ferromagnets, in direct analogy to the well-known proximity
effects in superconductivity.Comment: 4 pages, 3 figure
Variability in gene cassette patterns of class 1 and 2 integrons associated with multi drug resistance patterns in Staphylococcus aureus clinical isolates in Tehran-Iran
Background: To investigate antibiotic resistance, the occurrence and distribution of class 1 and 2 integrons in multidrug- resistant Staphylococcus aureus isolates from hospitals in Tehran, Iran. The isolates were examined for susceptibility to antimicrobial agents. The mecA gene, class 1 and 2 integrons were detected by PCR. Integrase positive strains were further analysed for the presence of resistance gene cassettes using specific primers and were sequenced. Results: Among 139S.aureus isolates, 109 (78.4 ) and 112 (80.5 ) strains were considered as multidrug resistant and mecA positive, respectively. Class 1 integrons and internal variable regions were found in 72.6 (101/139) and 97 (98/101) and class 2 integrons and variable regions also in 35.2 (49/139) and 65.3 (32/49) of S.aureus clinical isolates, respectively. Twelve distinct cassette arrays were found, containing genes encoding resistance to β-lactams, aminoglycosides, streptothricin, trimethoprim, chloramphenicol,a putative glucose dehydrogenase precursor and a protein with unknown function. Gene cassette arrays aadB, aadA2 and dhfrA1-sat2-aadA1 were common in S.aureus isolates. We detected a completely new gene cassettes which contained aadB, oxa2, aacA4, orfD-aacA4-catB8, aadB-catB3, orfD-aacA4 and aadB-aadA1-cmlA6 of class 1 and dhfrA1-sat2-aadA1, dhfrA11, dhfrA1-sat2 of class 2 integrons. Conclusions: This is the first study to report carriage of class 1 and 2 integrons and associated gene cassettes among in S.aureus isolates from Iran. © 2015 Mostafa et al
Video-rate, mid-infrared hyperspectral upconversion imaging
This is the final version. Available from Optical Society of America via the DOI in this recordIn this work we demonstrate, to the best of our knowledge, a novel wide field-of-view upconversion system, supporting upconversion of monochromatic mid-infrared (mid-IR) images, e.g., for hyperspectral imaging (HSI). An optical parametric oscillator delivering 20 ps pulses tunable in the 2.3–4 μm range acts as a monochromatic mid-IR illumination source. A standard CCD camera, in synchronism with the crystal rotation of the upconversion system, acquires in only 2.5 ms the upconverted mid-IR images containing 64 kpixels, thereby eliminating the need for postprocessing. This approach is generic in nature and constitutes a major simplification in realizing video-frame-rate mid-IR monochromatic imaging. A second part of this paper includes a proof-of-principle study on esophageal tissues samples, from a tissue microarray, in the 3–4 μm wavelength range. The use of mid-IR HSI for investigation of esophageal cancers is particularly promising as it allows for a much faster and possibly more observer-independent workflow than state-of-the-art histology. Comparing histologically stained sections evaluated by a pathologist to images obtained by either Fourier transform IR or upconversion HSI based on machine learning shows great promise for further work pointing towards clinical translation using the presented mid-IR HSI upconversion system.European CommissionH2020 Marie Skłodowska-Curie ActionsMinisterio de Ciencia, Innovación y UniversidadesGeneralitat de CatalunyaEuropean Social Fun
Health, Health-Related Quality of Life, and Quality of Life: What is the Difference?
The terms health, health-related quality of life (HRQoL), and quality of life (QoL) are used interchangeably. Given that these are three key terms in the literature, their appropriate and clear use is important. This paper reviews the history and definitions of the terms and considers how they have been used. It is argued that the definitions of HRQoL in the literature are problematic because some definitions fail to distinguish between HRQoL and health or between HRQoL and QoL. Many so-called HRQoL questionnaires actually measure self-perceived health status and the use of the phrase QoL is unjustified. It is concluded that the concept of HRQoL as used now is confusing. A potential solution is to define HRQoL as the way health is empirically estimated to affect QoL or use the term to only signify the utility associated with a health state
From fuzzy to annotated semantic web languages
The aim of this chapter is to present a detailed, selfcontained and comprehensive account of the state of the art in representing and reasoning with fuzzy knowledge in Semantic Web Languages such as triple languages RDF/RDFS, conceptual languages of the OWL 2 family and rule languages. We further show how one may generalise them to so-called annotation domains, that cover also e.g. temporal and provenance extensions
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