1,830 research outputs found

    The internal caustic structure of illuminated liquid droplets

    Get PDF
    The internal electric field of an illuminated liquid droplet is studied in detail using both wave theory and ray theory. The internal field obtains its maximum values on the caustics within the droplet. Ray theory is used to determine the equations of these caustics and the density of rays on them. The Debye series expansion of the interior field Mie amplitudes is used to calculate the wave theory version of these caustics. The physical interpretation of the sources of stimulated Raman scattering and fluorescence emission within a liquid droplet is then given

    Assessing the contributions of surface waves and complex rays to far-field Mie scattering by use of the Debye series

    Get PDF
    The contributions of complex rays and the secondary radiation shed by surface waves to scattering by a dielectric sphere are calculated in the context of the Debye series expansion of the Mie scattering amplitudes. Also, the contributions of geometrical rays are reviewed and compared with the Debye series. Interference effects between surface waves, complex waves, and geometrical waves are calculated, and the possibility of observing these interference effects is discussed. Experimental data supporting the observation of a surface wave-geometrical pattern is presented

    Gas temperature and density measurements based on spectrally resolved Rayleigh-Brillouin scattering

    Get PDF
    The use of molecular Rayleigh scattering for measurements of gas density and temperature is evaluated. The technique used is based on the measurement of the spectrum of the scattered light, where both temperature and density are determined from the spectral shape. Planar imaging of Rayleigh scattering from air using a laser light sheet is evaluated for ambient conditions. The Cramer-Rao lower bounds for the shot-noise limited density and temperature measurement uncertainties are calculated for an ideal optical spectrum analyzer and for a planar mirror Fabry-Perot interferometer used in a static, imaging mode. With this technique, a single image of the Rayleigh scattered light can be analyzed to obtain density (or pressure) and temperature. Experimental results are presented for planar measurements taken in a heated air stream

    Laser diffraction particle sizing: Instrument probe volume relocation and elongation

    Get PDF
    The effective probe volume of laser diffraction particle sizing instruments depends on many instrument parameters. In particular the probe volume axial boundaries and its location along laser beam are essentially defined by the onset of a vignetting effect where light scattered at large angles from small particles misses the transform lens. This vignetting effect results in a probe volume that must be inconveniently close to the lens in order to detect smaller diameter particles (less than 100 micrometers). With the addition of an appropriately designed Keplerian telescope, the probe volume may be relocated and elongated. The theory of operation of this supplemental optical system is described. Design considerations for these supplemental optical systems are described, including recommendations for lens specifications, assembly and use. An image transfer system is described which has been designed for use on a Malvern 2600HSD instrument. Experimental validation of this image transfer system is described

    Experimental testing of four correction algorithms for the forward scattering spectrometer probe

    Get PDF
    Three number density correction algorithms and one size distribution correction algorithm for the Forward Scattering Spectrometer Probe (FSSP) were compared with data taken by the Phase Doppler Particle Analyzer (PDPA) and an optical number density measuring instrument (NDMI). Of the three number density correction algorithms, the one that compared best to the PDPA and NDMI data was the algorithm developed by Baumgardner, Strapp, and Dye (1985). The algorithm that corrects sizing errors in the FSSP that was developed by Lock and Hovenac (1989) was shown to be within 25 percent of the Phase Doppler measurements at number densities as high as 3000/cc

    Viabilidade, aceitação e eficácia do tratamento familiar para anorexia nervosa em adolescentes: um estudo observacional no Brasil

    Get PDF
    OBJECTIVE: There is strong evidence that family-based treatment is effective in cases of adolescent anorexia nervosa. Although family-based treatment has been studied in English-speaking countries, there is a need to examine the generalizability of this approach to non-English speaking cultures. This pilot-study aimed to examine the feasibility, acceptability, and effectiveness of family-based treatment in Brazil. METHOD: Observational study of adolescents with anorexia nervosa (excluding menstrual criteria), as determined with the Diagnostic and Well-Being Assessment, referred for treatment at a specialized center in São Paulo, Brazil. The following data were collected at baseline, at the end of treatment, and after six months of follow-up: weight; height; body mass index; menstrual status; Eating Disorder Examination Questionnaire score; and Children Global Assessment of Functioning Scale score. RESULTS: Of 11 eligible patients/families, 9 (82%) enrolled in the study, and 7 (78%) completed the treatment. The mean patient age was 14.64 ± 1.63 years (range, 12.33-17.00 years). The Wilcoxon signed rank test showed statistically significant improvement in weight and body mass index at the end of treatment, as well as after six months of follow-up, at which point none of the patients met the diagnostic criteria for any eating disorder. CONCLUSION: The results suggest that family-based treatment is acceptable and feasible for Brazilian families. Outcomes suggest that the approach is effective in this cultural context, leading to improvements similar to those reported in previous studies conducted in other cultures.OBJETIVO: Estudos prévios demonstram fortes evidências de eficácia do Tratamento Familiar para anorexia nervosa em adolescentes. Os estudos disponíveis a respeito do tratamento familiar foram conduzidos em países de língua inglesa. É necessário avaliar a aplicabilidade deste método em países de língua não-inglesa. Este estudo piloto tem como objetivo avaliar a viabilidade, a aceitação e a eficácia do tratamento familiar no Brasil. MÉTODO: Estudo observacional de adolescentes com diagnóstico anorexia nervosa (exceto critério amenorréia) segundo o Levantamento sobre Diagnóstico e Bem-Estar de crianças e adolescentes encaminhadas para tratamento em um centro especializado na cidade de São Paulo, Brasil. Dados coletados no início do estudo, ao final do tratamento e seis meses após o término: peso, estatura, índice de massa corporal, menstruações, Questionário de Exame para Transtornos Alimentares e Escala de Funcionamento Global para Crianças. RESULTADOS: Nove de 11 famílias elegíveis entraram no estudo (82%) e sete (78%) completaram o tratamento. A idade média foi 14,64 anos (DP = 1,63; 12,33-17,00). Teste dos sinais de Wilcoxon demonstrou melhora estatisticamente significativa no peso e índice de massa corporal ao final do tratamento e seis meses após o término. Nenhum dos pacientes preencheu critérios diagnósticos para qualquer transtorno alimentar no seguimento. CONCLUSÃO: Os resultados sugerem que tratamento familiar é aceitável e viável para as famílias brasileiras. A evolução sugere que este método pode ser eficaz nesse contexto cultural com resultados positivos semelhantes a estudos prévios realizados em outras culturas

    Scattering of a Tightly Focused Beam by an Optically Trapped Particle

    Get PDF
    Near-forward scattering of an optically trapped 5 m radius polystyrene latex sphere by the trapping beam was examined both theoretically and experimentally. Since the trapping beam is tightly focused, the beam fields superpose and interfere with the scattered fields in the forward hemisphere. The observed light intensity consists of a series of concentric bright and dark fringes centered about the forward scattering direction. Both the number of fringes and their contrast depend on the position of the trapping beam focal waist with respect to the sphere. The fringes are caused by diffraction due to the truncation of the tail of the trapping beam as the beam is transmitted through the sphere

    A test of the DSM-5 severity specifier for bulimia nervosa in adolescents: Can we anticipate clinical treatment outcomes?

    Get PDF
    OBJECTIVE:This study tested clinical utility of the DSM-5 severity specifier for bulimia nervosa (BN) in predicting treatment response among adolescents (N = 110) within a randomized clinical trial of two psychosocial treatments. METHOD:Analyses grouped individuals meeting criteria for BN diagnosis by baseline severity, per DSM-5. Associations among baseline severity classification and BN behavior (i.e., binge eating and compensatory behavior) and eating disorder examination (EDE) Global scores at end-of-treatment (EOT), 6- and 12-month follow-up were examined. RESULTS:Associations between severity categories with BN symptoms were not significant at EOT, or follow-up. Test for linear trend in BN behavior was significant at EOT, F = 5.23, p = 0.02, without demonstrating a linear pattern. Relation between severity categories with EDE Global scores was significant at 6-month follow-up, F = 3.76, p = 0.01. Tests for linear trend in EDE Global scores were significant at EOT, F = 5.40, p = 0.02, and at 6 months, F = 10.73, p = 0.002, with the expected linear pattern. DISCUSSION:Findings suggest the DSM-5 BN severity specifier holds questionable utility in anticipating outpatient treatment response in adolescents with BN. The specifier may have improved ability to predict attitudinal rather than behavioral treatment outcomes
    corecore