Luminescence in sulfides : a rich history and a bright future

Sulfide-based luminescent materials have attracted a lot of attention for a wide range of photo-, cathodo- and electroluminescent applications. Upon doping with Ce3+ and Eu2+, the luminescence can be varied over the entire visible region by appropriately choosing the composition of the sulfide host. Main application areas are flat panel displays based on thin film electroluminescence, field emission displays and ZnS-based powder electroluminescence for backlights. For these applications, special attention is given to BaAl2S4:Eu, ZnS:Mn and ZnS:Cu. Recently, sulfide materials have regained interest due to their ability (in contrast to oxide materials) to provide a broad band, Eu2+-based red emission for use as a color conversion material in white-light emitting diodes (LEDs). The potential application of rare-earth doped binary alkaline-earth sulfides, like CaS and SrS, thiogallates, thioaluminates and thiosilicates as conversion phosphors is discussed. Finally, this review concludes with the size-dependent luminescence in intrinsic colloidal quantum dots like PbS and CdS, and with the luminescence in doped nanoparticles

Ultrafast exciton dephasing in PbS colloidal quantum dots

In this work, we have measured the ground state excitonic dephasing in PbS QDs of sizes from 3.7nm to 5.7nm diameter in the temperature range from 5K to 100K by transient degenerate four-wave mixing (FWM) using 100fs pulses. A combination of heterodyne and k-selection detection was implemented to increase sensitivity and enable 4 orders of magnitude dynamic range in the FWM field detection

Evolution of near UV Halley's spectrum in the inner coma

A direct way to observe the photodissociation of water vapor in a cometary coma is to detect the OH prompt emission. This emission is shifted of delta lambda = 4 nm with respect to the OH 309 nm fluorescence band. The extended data set obtained with the three-channel spectrometer on-board Vega 2 reveals at short distance of the nucleus (i.e., less than 600 km) an excess of emission on the right wing of the OH band which may be interpreted as being mainly due to prompt emission

Dust and gas jets: Evidence for a diffuse source in Halley's coma

The distribution of dust-scattered intensity in Halley's inner coma is measured with the Vega three-channel spectrometer at three selected wavelengths: 377, 482, and 607 nm. The variation along a cometo-centric radius may be described by a p(sup -s) law where p is the distance between nucleus and optical axis and s is an exponent which is equal to 1 except in an intermediate 3000 less than p less than 7000 km region where s = 1.5. The shape of the radial distribution may be explained with a model including solar radiation pressure effect and quantum scattering efficiencies calculated from Mie theory. Monochromatic images inside an angular sector having its apex at the nucleus show evidence of two dust jets which extend to 40,000 Km. The pixel-to-pixel ratio of two images of dust intensity at 377 and 482 nm shows that the scattered intensity presents an excess of blue coloration in a zone located around the jets between 10,000 and 25,000 km. This coloration is interpreted as being due to a population of sub-micronic grains which result of the fragmentation of dust particles transported in the jets. It is suggested that the diffuse source where an additional quantity of CO was detected might be connected with the presence of a dust jet. In the present scheme, grain particles with a size of several micron or 10 micron would be transported inside a dust jet to distances of several 10,000 km where they would suffer fragmentation and produce sub-micronic particles and a release of gas which would be at the origin of the diffuse source

Family size and intergenerational social mobility during the fertility transition

It has been argued in sociology, economics, and evolutionary anthropology that family size limitation enhances the intergenerational upward mobility chances in modernized societies. If parents have a large flock, family resources get diluted and intergenerational mobility is bound to head downwards. Yet, the empirical record supporting this resource dilution hypothesis is limited. This article investigates the empirical association between family size limitation and intergenerational mobility in an urban, late nineteenth century population in Western Europe. It uses life course data from the Belgian city of Antwerp between 1846 and 1920. Findings are consistent with the resource dilution hypothesis: after controlling for confounding factors, people with many children were more likely to end up in the lower classes. Yet, family size limitation was effective as a defensive rather than an offensive strategy: it prevented the next generation from going down rather than helping them to climb up the social ladder. Also, family size appears to have been particularly relevant for the middle classes. Implications for demographic transition theory are discussed.Belgium, demographic transition, fertility, nineteenth century, parental investment, quantity-quality trade-off, resource dilution, social mobility

Migration and reproduction in transitional times: stopping behavior of immigrants and natives in the Belgian city of Antwerp (1810-1925)

"In the course of the nineteenth century, millions of migrants moved to and settled permanently in western European urban centers. This large influx of immigrants, originating from various regions with different demographic backgrounds, affected the level and pace of the local fertility transition. In this study the authors sampled and analyzed 747 couples consisting of natives and immigrants in the city of Antwerp during the early fertility transition. Stopping behavior of both native, immigrant and mixed couples is analyzed. The authors found that adult migrants display stopping behavior that resembles that at their origin while individuals that immigrated during childhood adapt more often to the dominant local fertility pattern. While the migratory status of the mother was more decisive than that of the father, couples consisting of both immigrants were the last to implement more efficient reproductive strategies. By focusing on individual behavioral patterns, new light is shed on the diffusion of reproductive behavior during the Western European fertility decline." (author's abstract

A systematic review of infected descending thoracic aortic grafts and endografts

Objective: The objective of this study was to collect and critically analyze the current evidence on the modalities and results of treatment of descending thoracic aortic surgical graft (SG) and endograft (EG) infection, which represents a rare but dramatic complication after both surgical and endovascular aortic repair. Methods: A comprehensive electronic health database search (PubMed/MEDLINE, Scopus, Google Scholar, and the Cochrane Library) identified all articles that were published up to October 2017 reporting on thoracic aortic SG or EG infection. Observational studies, multicenter reports, single-center series and case reports, case-control studies, and guidelines were considered eligible if reporting specific results of treatment of descending thoracic aortic SG or EG infection. Comparisons of patients presenting with SG or EG infection and between invasive and conservative treatment were performed. Odds ratio (OR) meta-analyses were run when comparative data were available. Results: Forty-three studies reporting on 233 patients with infected SG (49) or EG (184) were included. Four were multicenter studies including 107 patients, all with EG infection, associated with a fistula in 91% of cases, with a reported overall survival at 2 years of 16% to 39%. The remaining 39 single-center studies included 49 patients with SG infection and 77 with EG infection. Association with aortoesophageal fistula was significantly more common with EG (60% vs 31%; P = .01). In addition, time interval from index procedure to infection was significantly shorter with EG (17 +/- 21 months vs 32 +/- 61 months; P = .03). Meta-analysis showed a trend of increased 1-year mortality in patients with SG infection compared with EG infection (pooled OR, 3.6; 95% confidence interval, 0.9-14.7; P = .073). Surgical management with infected graft explantation was associated with a trend toward lower 1-year mortality compared with graft preservation (pooled OR, 0.3; 95% confidence interval, 0.1-1.0; P = .056). Conclusions: Thoracic aortic EG infection is likely to occur more frequently in association with aortoesophageal fistulas and in a shorter time compared with SG infection. Survival is poor in both groups, especially in patients with SG infection. Surgical treatment with graft explantation seems to be the preferable choice in fit patients