865 resultados para Mirror


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Objective: To assess the impact of treatment foster care (TFC) on psychosocial and behavioral outcomes, delinquency, placement stability, and discharge status for children and adolescents who, for reasons of severe medical, social, psychological and behavioural problems, were placed in out-of-home care in restrictive settings or at risk of placement in such settings. Method: Electronic bibliographic databases, web searches, and article reference lists were used to identify randomized controlled trials (RCTs) investigating the effectiveness of TFC with children and young people. The Cochrane Collaboration’s criteria were used to assess the methodological quality of studies that met the inclusion criteria. Wherever possible, extracted outcome data from similar studies were synthesized with random effects meta-analyses. Results: A total of 5 studies including 390 participants were included in this review. Data suggest that TFC may be a useful intervention for children and young people with complex emotional, psychological, and behavioural need, who are at risk of placements in nonfamily settings that restrict their liberty and opportunities for social inclusion. Conclusion: Although the inclusion criteria for this systematic review set a study design threshold higher than that of previous reviews, the findings mirror those of earlier reviews. While the results of individual studies generally indicate that TFC is a promising intervention for children and youth experiencing mental health problems, behavioral problems, or problems of delinquency, the evidence base is not robust and more research is needed due to the limited number of studies in this area.

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We report on the characterization of the specular reflection of 50 fs laser pulses in the intensity range 10(17)-10(21)Wcm(-2) obliquely incident with p-polarization onto solid density plasmas. These measurements show that the absorbed energy fraction remains approximately constant and that second harmonic generation (SHG) achieves efficiencies of 22 +/- 8% for intensities approaching 10(21)Wcm(-2). A simple model based on the relativistic oscillating mirror concept reproduces the observed intensity scaling, indicating that this is the dominant process involved for these conditions. This method may prove to be superior to SHG by sum frequency mixing in crystals as it is free from dispersion and retains high spatial coherence at high intensity.

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We study a device formed by a Bose-Einstein condensate (BEC) coupled to the field of a cavity with a moving end mirror and find a working point such that the mirror-light entanglement is reproduced by the BEC-light quantum correlations. This provides an experimentally viable tool for inferring mirror-light entanglement with only a limited set of assumptions. We prove the existence of tripartite entanglement in the hybrid device, persisting up to temperatures of a few milli-Kelvin, and discuss a scheme to detect it.

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We present surface enhanced Raman optical activity (SEROA), as well as Raman, SERS and ROA, spectra of D- and L-ribose. By employing a gel forming polyacrylic acid to control colloid aggregation and associated birefringent artefacts we observe the first definitive proof of SEROA through measurement of mirror image bands for the two enantiomers.

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We examine lateralization of lateral displays in convict cichlids, Amatitlania nigrofasciata, and show a population level preference for showing the right side. This enables contesting pairs of fish to align in a head-to-tail posture, facilitating other activities. We found individuals spent a shorter mean time in each left compared with each right lateral display. This lateralization could lead to contesting pairs using a convention to align in a predictable head-to-tail arrangement to facilitate the assessment of fighting ability. It has major implications for the common use of mirror images to study fish aggression, because the 'opponent' would never cooperate and would consistently show the incorrect side when the real fish shows the correct side. With the mirror, the 'normal' head-to-tail orientation cannot be achieved.

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Background: Treatment foster care (TFC) is a foster family-based intervention that aims to provide young people (and, where appropriate, their families) with a tailored programme designed to effect positive changes in their lives. TFC was designed specifically to cater for the needs of children whose difficulties or circumstances place them at risk of multiple placements and/or more restrictive placements such as hospital or secure residential or youth justice settings.

Objectives: To assess the impact of TFC on psychosocial and behavioural outcomes, delinquency, placement stability, and discharge status for children and adolescents who require out-of-home placement.

Search methods: We searched the Cochrane Controlled Trials Register (CENTRAL) 2006 (Issue 4), MEDLINE (1966 to January 2007), CINAHL (1982 to December 2006), PsycINFO (1872 to January 2007), ASSIA (1987 to January 2007), LILACS (1982 to January 2007), ERIC (1966 to January 2007), Sociological Abstracts (1963 to January 2007), and the National Research Register 2006 (Issue 4).

Selection criteria: Included studies were randomised controlled trials investigating the effectiveness of TFC with children and young people up to the age of 18 who, for reasons of severe medical, social, psychological and behavioural problems, were placed in out of home care in restrictive settings (e.g. secure residential care, psychiatric hospital) or at risk of placement in such settings.

Data collection and analysis: Titles and abstracts identified in the search were independently assessed for eligibility by the two authors (GM and WT) who also extracted and entered into REVMAN. Date were synthesised on the few occasions where this was possible. Results are presented in tabular, graphical (forest plots) and textual form.

Main results: Five studies including 390 participants were included in this review. Data suggest that treatment foster care may be a useful intervention for children and young people with complex emotional, psychological and behavioural need, who are at risk of placements in nonfamily settings that restrict their liberty and opportunities for social inclusion.

Authors’ conclusions: Although the inclusion criteria for this systematic review set a study design threshold higher than that of previous reviews, the results mirror those of earlier reviews but also highlights the tendency of the perceived effectiveness of popular interventions to outstrip their evidence base. Whilst the results of individual studies generally indicate that TFC is a promising intervention for children and youth experiencing mental health problems, behavioural problems or problems of delinquency, the evidence base is less robust than that usually reported.The Cochrane Database of Systematic Reviews is a peer reviewed, international journal, published electronically each month. The 2010 Inpact Factor for the Cochrane Database of Systematic Reviews was 6.185.The CDSR is now ranked in the top 10 of the 151 in the Medicine, General & Internal category.

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We measure the two-dimensional, near-field spatial distribution of a 140-Angstrom nickel-like silver x-ray laser at the output aperture with high magnification using a curved multilayer x-ray mirror to image the output onto an x-ray charge-coupled device camera. Lasing is created by illuminating silver slab targets with a pair of 75 ps laser pulses separated by 2.2 nsec from the Vulcan laser. The two-dimensional, high-resolution, spatial image shows the x-ray laser source size and its position relative to the target surface. A dramatic change in both the position and source size are observed for the refraction compensating curved target as compared with the flat targets.

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Coupling of a soft X-ray laser beam with a relaying concave mirror in a sequentially pumped amplifier geometry using the Ne-like Ge system has been studied experimentally. Preliminary observations indicate an increase in the spatial coherence of the amplified relayed beam. In addition, near-field imaging of one of the amplifier plasmas shows a double-lobed intensity pattern of the emergent beam indicating refractive guiding of the amplified beam with components both normal and tangential to the target surface.

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A half-cavity using a multilayer mirror has been set up close to the end of a large gain germanium-target system. An unambiguous saturation behaviour of the 232 angstrom and 236 angstrom lines has been observed. The role of the cavity mirror in this result is discussed. Suggestions are made for practical applications of an XUV laser in this wavelength range.

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From measurements of spatial coherence and beam divergence of Ge soft x-ray laser at a far field, the x-ray laser beam has been characterized as a partially coherent Gaussian beam. Double-pass amplification will improve spatial and temporal coherence, spectral brightness and efficiency. Close to 100% geometrical coupling efficiency has been obtained in double pass amplification in Ge. Transient loss of feedback is attributed to mirror structure damage within the build-up time of the x-ray laser. Prospect for generation of coherent x-ray laser beam is discussed.

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Amplification of spontaneous emission at 23.6 nm has been studied in a Ge plasma heated by a 1 TW, 1.06 mum wavelength, laser pulse. The exponent of the axial gain reached 21 in a geometry with Fresnel number less-than-or-equal-to 1. Two plasma columns were produced by irradiation of slab targets up to a combined length of 3.6 cm. A narrow band XUV mirror allowed double pass amplification. Saturation of ASE output at 23.6 nm was observed as a change from exponential to linear growth of the output with plasma length. Further evidence of the effect was provided by a decline in the ratio of the output at 23.6 nm to that at 23.2 nm from approximately 1.6: 1 to approximately 0.5: 1, the latter being the theoretically predicted value for saturated operation. The onset of saturation at gL almost-equal-to 15 is consistent with model calculations. The beam divergence was about 8x diffraction limited with a brightness estimated at almost-equal-to 10(14) W/cm2/ster.

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Amplification of spontaneous emission (ASE) at 23.6 nm has been studied in a Ge plasma heated by a 1 TW infrared laser pulse. The exponent of the axial gain reached 21 in a geometry with Fresnel number less-than-or-equal-to 1. Two plasma columns of combined length up to 36 mm were used with an extreme ultraviolet mirror giving double-pass amplification. Saturation of the ASE output was observed. The beam divergence was about 8 x diffraction limited with a brightness estimated at 10(14) W cm-2 sr-1. The feedback from the mirror was significantly reduced probably by radiation damage from the plasma.

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As the state of the art for high power laser systems increases from terawatt to petawatt level and beyond, a crucial parameter for routinely monitoring high intensity performance is laser spot size on a solid target during an intense interaction in the tight focus regime ( 10(19) Wcm(-2) is demonstrated experimentally and shown to provide the basis for an effective focus diagnostic. Importantly, this technique is also shown to allow in-situ diagnosis of focal spot quality achieved after reflection from a double plasma mirror setup for very intense high contrast interactions (> 10(20) Wcm(-2)) an important application for the field of high laser contrast interaction science.

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When a pulse of light reflects from a mirror that is travelling close to the speed of light, Einstein's theory of relativity predicts that it will be up-shifted to a substantially higher frequency and compressed to a much shorter duration. This scenario is realized by the relativistically oscillating plasma surface generated by an ultraintense laser focused onto a solid target. Until now, it has been unclear whether the conditions necessary to exploit such phenomena can survive such an extreme interaction with increasing laser intensity. Here, we provide the first quantitative evidence to suggest that they can. We show that the occurrence of surface smoothing on the scale of the wavelength of the generated harmonics, and plasma denting of the irradiated surface, enables the production of high-quality X-ray beams focused down to the diffraction limit. These results improve the outlook for generating extreme X-ray fields, which could in principle extend to the Schwinger limit.

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The application of microbeams is providing new insights into the actions of radiation at the cell and tissue levels. So far, this has been achieved exclusively through the use of collimated charged particles. One alternative is to use ultrasoft X rays, focused by X-ray diffractive optics. We have developed a unique facility that uses 0.2-0.8-mm-diameter zone plates to focus ultrasoft X rays to a beam of less than 1 mum diameter. The zone plate images characteristic K-shell X rays of carbon or aluminum, generated by focusing a beam of 5-10 keV electrons onto the appropriate target. By reflecting the X rays off a grazing-incidence mirror, the contaminating bremsstrahlung radiation is reduced to 2%. The focused X rays are then aimed at selected subcellular targets using rapid automated cell-finding and alignment procedures; up to 3000 cells per hour can be irradiated individually using this arrangement. (C) 2001 by Radiation Research Society.