One-Pot Synthesis of Single-Source Precursors for Nanocrystalline LED Phosphors M2Si5N8:Eu2+ (M = Sr, Ba)

Highly efficient red-emitting nitridosilicate phosphors Sr2Si5N8:Eu2+ and Ba1.5Sr0.5Si5N8:Eu2+ (doping level 1%) applicable to phosphor converted pc-LEDs were synthesized in nanocrystalline form at low temperatures employing a novel single-source precursor approach. Synthesis starts from nanocrystalline silicon and uses mixed metal amides M(NH2)2 with M = Sr, Ba, Eu as reactive intermediates. In a second approach, a single-source precursor mixture obtained from a one-pot reaction of the corresponding elements (Sr/Ba, Eu, Si) was obtained in supercritical ammonia. Thermoanalytical in situ investigations gain a deeper insight into the degradation mechanism of the mixed metal amide precursors and revealed the onset for the formation of the 2-5-8 phosphor materials at temperatures slightly above 900°C. Formation of the products is complete below 1400°C. Under these conditions, the nitridosilicate phosphors form spherically shaped particles with crystallites of 200 nm in size. Spherical particles are desirable for phosphor application because light extraction may be improved by decreased light trapping and re-absorption losses. As a major advantage of the one-pot precursor approach, the exact Sr/Ba content in the solid solution series Sr2−xBaxSi2N8:Eu2+ and the doping concentration of Eu2+ can easily be controlled in a wide range by the relative amount of the elemental starting materials (Sr, Ba, Eu, Si). Simultaneously, thorough mixing of these elements down to an atomic level (Sr, Ba, Eu) or at least at nanoscopic dimensions (silicon) is achieved by the solution approach. As a consequence, no milling and pre-reaction steps are necessary which might give rise to contamination. Advantageously, this approach can easily be extended to large-scale processes by simultaneously preserving complete mixing. Furthermore, the influence of the starting materials (single-source precursor, nanocrystalline silicon) and the reaction conditions on the crystal shape and finally on the luminescence properties of the products was investigated. The obtained nanophosphors exhibit luminescence properties comparable to coarsely crystalline nitridosilicate phosphor powders prepared by conventional high-temperature processing

A Tachyonic Gluon Mass: Between Infrared and Ultraviolet

The gluon spin coupling to a Gaussian correlated background gauge field induces an effective tachyonic gluon mass. It is momentum dependent and vanishes in the UV only like 1/p^2. In the IR, we obtain stabilization through a positive m^2_{conf}(p^2) related to confinement. Recently a purely phenomenological tachyonic gluon mass was used to explain the linear rise in the q\bar q static potential at small distances and also some long standing discrepancies found in QCD sum rules. We show that the stochastic vacuum model of QCD predicts a gluon mass with the desired properties.Comment: 10 pages LaTeX, 2 figures using eps

Causes of brain dysfunction in acute coma: a cohort study of 1027 patients in the emergency department

BACKGROUND: Coma of unknown etiology (CUE) is a major challenge in emergency medicine. CUE is caused by a wide variety of pathologies that require immediate and targeted treatment. However, there is little empirical data guiding rational and efficient management of CUE. We present a detailed investigation on the causes of CUE in patients presenting to the ED of a university hospital. METHODS: One thousand twenty-seven consecutive ED patients with CUE were enrolled. Applying a retrospective observational study design, we analyzed all clinical, laboratory and imaging findings resulting from a standardized emergency work-up of each patient. Following a predefined protocol, we identified main and accessory coma-explaining pathologies and related these with (i.a.) GCS and in-hospital mortality. RESULTS: On admission, 854 of the 1027 patients presented with persistent CUE. Their main diagnoses were classified into acute primary brain lesions (39%), primary brain pathologies without acute lesions (25%) and pathologies that affected the brain secondarily (36%). In-hospital mortality associated with persistent CUE amounted to 25%. 33% of patients with persistent CUE presented with more than one coma-explaining pathology. In 173 of the 1027 patients, CUE had already resolved on admission. However, these patients showed a spectrum of main diagnoses similar to persistent CUE and a significant in-hospital mortality of 5%. CONCLUSION: The data from our cohort show that the spectrum of conditions underlying CUE is broad and may include a surprisingly high number of coincidences of multiple coma-explaining pathologies. This finding has not been reported so far. Thus, significant pathologies may be masked by initial findings and only appear at the end of the diagnostic work-up. Furthermore, even transient CUE showed a significant mortality, thus rendering GCS cutoffs for selection of high- and low-risk patients questionable. Taken together, our data advocate for a standardized diagnostic work-up that should be triggered by the emergency symptom CUE and not by any suspected diagnosis. This standardized routine should always be completed - even when initial coma-explaining diagnoses may seem evident

Phonological priming and phonetic carry-over in two Danish-English bilinguals

In this study we investigate whether the phonetic carry-over effects (or gestural drift) reported in the literature as occurring in the speech of bilinguals after long-term phonological priming (i.e., several months), also occur after short-term priming of less than all hour. Two bilingual Danish-English speakers were asked to read word lists after being primed for some time in one or other of their languages. In the Danish mode, a number of switches into English occurred in the word-list, and in the English mode switches into Danish were included. The switches allowed the examination of three possible carry-over effects: two with vowels and one with consonants. The results demonstrated no effect with the switches that would require the greatest phonetic change. They also showed that some potential carry-over effects were more likely long-term interference pattems. Acoustic aualysis did suggest that with one of the vowel switches carry-over effects going both ways between Danish and English and English and Danish did occur, although this was clearer with one subject than the other

The Ca II infrared triplet's performance as an activity indicator compared to Ca II H and K

Aims. A large number of Calcium Infrared Triplet (IRT) spectra are expected from the GAIA- and CARMENES missions. Conversion of these spectra into known activity indicators will allow analysis of their temporal evolution to a better degree. We set out to find such a conversion formula and to determine its robustness. Methods. We have compared 2274 Ca II IRT spectra of active main-sequence F to K stars taken by the TIGRE telescope with those of inactive stars of the same spectral type. After normalizing and applying rotational broadening, we subtracted the comparison spectra to find the chromospheric excess flux caused by activity. We obtained the total excess flux, and compared it to established activity indices derived from the Ca II H & K lines, the spectra of which were obtained simultaneously to the infrared spectra. Results. The excess flux in the Ca II IRT is found to correlate well with $R_\mathrm{HK}'$ and $R_\mathrm{HK}^{+}$, as well as $S_\mathrm{MWO}$, if the $B-V$-dependency is taken into account. We find an empirical conversion formula to calculate the corresponding value of one activity indicator from the measurement of another, by comparing groups of datapoints of stars with similar B-V.Comment: 16 pages, 15 figures. Accepted for publication in Astronomy & Astrophysic

Bayesian estimation applied to multiple species

Observed data are often contaminated by undiscovered interlopers, leading to biased parameter estimation. Here we present BEAMS (Bayesian estimation applied to multiple species) which significantly improves on the standard maximum likelihood approach in the case where the probability for each data point being “pure” is known. We discuss the application of BEAMS to future type-Ia supernovae (SNIa) surveys, such as LSST, which are projected to deliver over a million supernovae light curves without spectra. The multiband light curves for each candidate will provide a probability of being Ia (pure) but the full sample will be significantly contaminated with other types of supernovae and transients. Given a sample of N supernovae with mean probability, ⟨P⟩, of being Ia, BEAMS delivers parameter constraints equal to N⟨P⟩ spectroscopically confirmed SNIa. In addition BEAMS can be simultaneously used to tease apart different families of data and to recover properties of the underlying distributions of those families (e.g. the type-Ibc and II distributions). Hence BEAMS provides a unified classification and parameter estimation methodology which may be useful in a diverse range of problems such as photometric redshift estimation or, indeed, any parameter estimation problem where contamination is an issue

Engineering NK Cells for CAR Therapy—Recent Advances in Gene Transfer Methodology

The development of chimeric antigen receptor (CAR) T cell therapy has introduced a new and effective strategy to guide and promote the immune response against tumors in the clinic. More recently, in an attempt to enhance its utility, this method has been expanded to novel cell types. One of the more successful variants has proven to be the expression of CARs in Natural Killer (NK) cells (CAR-NK). Gene engineering NK cells to express an exogenous CAR receptor allows the innate anti-tumor ability of NK cells to be harnessed and directed against a target tumor antigen. In addition, the biology of NK cells allows the development of an allogeneic cell therapeutic product useable with most or all patient haplotypes. NK cells cause little or no graft versus host disease (GvHD) and are therefore suitable for development of an "off the shelf" therapeutic product. Initial trials have also shown that CAR-NK cells rarely cause cytokine release syndrome. However, despite their potential NK cells have proven to be difficult to engineer, with high sensitivity to apoptosis and low levels of gene expression. The creation of optimized methods to introduce genes into NK cells will promote the widespread application of CAR-NK in research laboratories and the clinics

The Value of Verbal Feedback in Allocation Decisions

Depending on the context at hand, people’s preference for receiving feedback might differ. Especially in allocation decisions that directly concern another individual, feedback from the affected person can have positive or negative value. We study such preferences in a laboratory experiment by eliciting the willingness-to-pay to receive or to avoid verbal feedback from subjects that were previously affected by an allocation decision. We find that most decision makers exhibit a positive willingness-to-pay for having control about whether feedback occurs or not. Specifically, decision makers that equally shared their endowment with the recipient revealed a positive willingness-to-pay for receiving, but not for avoiding feedback. By contrast, among decision makers that behaved selfishly, we identify both: subjects that were willing to pay for receiving and subjects that were willing to pay for avoiding feedback. The stated motivations indicate that curiosity, the desire to receive social approval and giving the recipient the chance to express his/her feelings are the main reasons for feedback acquisition, while shame and fear of negative feedback are the main reasons for avoidance