• Control over purity and particle morphology.• Non-hazardous.• Reasonable production costs.While for certain conversion colors solutions close to the ideal have been found, there remains work to be done, especially for phosphors which emit in the red. This article will highlight the classic solutions for white pcLEDs and show the remaining challenges. In addition, an account will be given of recent developments involving semiconductor light sources with high radiance and high lumen output, where the color conversion of blue laser diodes for digital projection and automotive applications poses new challenges to materials research. Luminescent Materials: The State of the Art Yellow-Emitting MaterialsToday, almost all single-phosphor pcLEDs are based on Ce 3+ -doped yttrium aluminum garnet (Y 3 Al 5 O 12 , YAG:Ce) [ 5,6 ] or, sometimes, Eu 2+ -doped orthosilicate phosphors (Sr, Ba, Mg) 2 SiO 4 , [7][8][9][10][11][12][13] as the yellow-emitting luminescent material. However, stability issues of the orthosilicates have not been fully overcome: this has limited the commercial use of this material class.The emission color of YAG:Ce can be tuned by substitution of lattice constituents, e.g., Y may be replaced by Lu (Lutetium), Gd (Gadolinium), or Tb (Terbium), and Al may be replaced by Ga (Gallium). The emission spectrum is shown in Figure 1 . This material fulfi lls all of the stated requirements and therefore can be considered an archetypal LED phosphor material. [ 14,15 ] The excitation spectrum for YAG:Ce at 440-460 nm is well matched to the emission of blue LEDs and its yellow dual ground-state broadband emission in the visible spectral region (500-700 nm) provides a reasonable CRI. Such a single-phosphor approach may be very simple and effi cient, but it has one major drawback: the limited spectral power distribution in the red spectral range causes a CCT > 4000 K (cool white light) and a low CRI (usually below 80). Particularly for indoor illumination, a higher CRI and lower (i.e., warmer) CCT (2700-3200 K) are preferable. Suitable white light LEDs can be produced using a two-phosphor approach, wherein a yellow phosphor (YAG:Ce) is combined with a red one.The effi cient generation of white light by phosphor-converted LEDs (pcLEDs) suffers from a trade-off between high color rendition, low correlated color temperatures, and luminous effi cacy. While this is partially an inherent problem, it is also caused by the spectral effi ciency of the materials used. The particular challenges for materials research lie, amongst the demanding general requirements, in fi nding very narrow-band or line-emitting materials: excitable with blue light, emitting in the near red. A way to design Mn(IV) activated line emitters is proposed, and methods for high-throughput combinatorial syntheses are specifi ed.
Background Patients increasingly use health portals and Web-based expert forums (ask-the-doctor services), but little is known about the specific needs of Internet users visiting such websites, the nature of their requests, or how satisfied they are with Internet health experts.Objective The aim of this study was to analyze the information requests of (mostly female) patients visiting an Internet expert forum on involuntary childlessness and their satisfaction with the experts' feedback.Methods We posted an electronic questionnaire on a website hosting an expert forum on involuntary childlessness. The questionnaire was “activated” whenever a visitor sent a question or request to the expert forum. The survey focused on the reasons for visiting the expert forum and whether the visitors were satisfied with the experts' answers to previously posted questions. The free-text questions of visitors who answered the survey were analyzed using Atlas-ti, a software program for qualitative data analysis.ResultsOver a period of 6 months, 513 out of 610 visitors (84%) answered the questionnaire. The majority of respondents (65.5%) expected general information about involuntary childlessness, conception, or an evaluation of drugs. Others were concerned about their actual treatment (40.6%) and therapeutic options (28.8%). Out of 225 respondents who had previously contacted the forum, 223 had received an answer, and 123 (55.2%) were satisfied with the experts' answers. About half (105/223) of those users who had previously received an answer from the expert forum stated that they had discussed it with their own doctor. More of these users were satisfied with their subsequent care in fertility clinics than users who did not talk to their doctor about their Internet activities (93.9% vs 76.1%; P = .015 ). According to the qualitative analysis, many requests (n = 194) were more or less trivial, especially those for information on basic aspects of reproduction. More than one-third of visitors (n = 199) sent detailed results of diagnostic tests and asked for a first or second opinion. Requests to the expert forum were also sent in order to obtain emotional support (17%) or to complain about a doctor (15%).Conclusions Visitors who sent their laboratory findings to receive a thorough evaluation or a second opinion had a good command of the opportunities that an expert forum offers. One important expectation of the forum was emotional support, indicating psychological needs that were not met by medical providers. Future websites must find a compromise in order to protect experts from being overwhelmed by general, nonspecific requests while supporting patients with individualized answers.
The increased fibrin specificity and single bolus administration of TNK-tPA do not increase the risk of intracranial haemorrhage but are associated with less non-cerebral bleeding, especially amongst high-risk patients.
Background: Studies investigating the longitudinal predictive value of burnout on both effort-reward imbalance (within the working place) and work-family conflict (between work and private life) in residents are lacking. Former cross-sectional studies showed an association of effort-reward imbalance and work family conflict with an elevated burnout risk in physicians. Methods: Data acquisition was carried out within the multi-centric, longitudinal, and prospective "KarMed" study in Germany from 2009 until 2016. Yearly surveys including validated scales: the Maslach Burnout Inventory with its three subscales (emotional exhaustion, personal accomplishment, depersonalisation), the Work-Family Conflict Scale, and the Effort-Reward Imbalance Inventory. Further independent variables were gender and parental status.The analyses were based on general linear models and general linear mixed models with repeated measures designs. Results: Significant time-fixed effects were found for all three subscales of the Maslach Burnout Inventory, with gender effects on the subscales emotional exhaustion and depersonalisation. The parental status had no significant effect on burnout. All estimated means for burnout during 6 years of postgraduate training were higher when work-family conflict and gratification crisis were taken into account. Personal accomplishment increased continuously over time as well showing neither gender differences nor influences by the parental status. Conclusions: Personal accomplishments might act as a buffer compensating to some extent for the physicians' stress experience. Given that burnout may be associated with poor patient care, there is a need to reduce burnout rates and their associated factors in resident physicians.
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