CLIMATE CHANGE AND VECTOR-BORNE DISEASES IN SOUTHERN EUROPE

Vector-borne infections have always caused suffering throughout the history. Thealliance of arthropods and microorganisms is hard to defeat as insecticides anddrugs proved to be temporary solutions. Since our questionable victory overmalaria and yellow fever in the midst of the last century, vectors gradually broadentheir sovereignty in the presence of our oblivion. The infrastructure for surveillanceand control of vectors is neglected and in the last decades we tend to prioritizechronic diseases rather than infections. Expanding air travel and marine transport,increasing global trade and travel provoked the globalization of vectors andpathogens. Climate change, especially the northerly stretch of temperate zonepromote and sustain the incursion of exotic vectors like Aedes albopictus inSouthern Europe bringing along tropical diseases like Chikungunya. Denguebecoming hyperendemic around the world is looking for a competent vector inSouthern Europe while Aedes aegypti is trying to take hold in Portugal and Spain.West Nile Virus, an emerging encephalitis threat is gradually increasing itsepidemic potential in Europe. The widening man-made environments andanthropogenic changes like global warming affect the behavior and populationdynamics of vectors as well as the evolution of pathogens causing dramatic changesin disease prevalence and even severity. Today we may well be in the brink ofresurgence of vector-borne infections so we need to assess current and future risks,and conduct effective surveillance

Resonant nonradiative energy transfer in CdSe/ZnS core/shell nanocrystal solids enhances hybrid white light emitting diodes

Cataloged from PDF version of article.We propose and demonstrate hybrid white light emitting diodes enhanced with resonant nonradiative energy transfer in CdSe/ZnS core/shell nanocrystal solids integrated on near-UV InGaN/GaN LEDs. We observe a relative quantum efficiency enhancement of 13.2 percent for the acceptor nanocrystals in the energy gradient mixed assembly, compared to the monodisperse phase. This enhancement is attributed to the ability to recycle trapped excitons into nanocrystals using nonradiative energy transfer. We present the time-resolved photoluminescence of these nanocrystal solids to reveal the kinetics of their energy transfer and their steady-state photoluminescence to exhibit the resulting quantum efficiency enhancement

Onion-Like (CdSe)ZnS/CdSe/ZnS quantum-dot-quantum-well heteronanocrystals for investigation of multi-color emission

Cataloged from PDF version of article.We investigate multi-color spontaneous emission from quantum-dot-quantum-well heteronanocrystals made of onion-like (CdSe) ZnS/CdSe/ZnS ( core) shell/shell/shell structures, with our theoretical results explaining experimental measurements for the first time. In such multi-layered heteronanocrystals, we discover that the carrier localization is tuned from type-1-like to type-2-like localization by controlling CdSe and ZnS shell thicknesses, and that 3-monolayer ZnS barriers are not necessarily sufficient for carrier localization, unlike in conventional ( CdSe) ZnS ( core) shell structures. We demonstrate that exciton localization in distinct layers of ( CdSe) ZnS/CdSe/ZnS heteronanocrystals with high transition probability ( for n=1 states in CdSe core and n=2 states in CdSe shell) is key to their multi-color emission. (c) 2008 Optical Society of America

Excitation resolved color conversion of CdSe/ZnS core/shell quantum dot solids for hybrid white light emitting diodes

Cataloged from PDF version of article.In this paper, for their use as nanoluminophors on color-conversion white light emitting diodes (LEDs), we present spectrally resolved relative quantum efficiency and relative color (photon) conversion efficiency of CdSe/ZnS core/shell nanocrystal (NC) emitters in the solid-state film. We observe that both the averaged relative quantum efficiency and the averaged relative photon conversion efficiency of these NC solids increase with the increasing photon pump energy. Therefore, the excitation LED platform emitting at shorter wavelengths facilitates such NC luminophor solids to be more efficiently pumped optically. Furthermore, we investigate the spectral time-resolved spectroscopy of NCs in solution and in film with 0.4-2.4 nmol integrated number of NCs in the spectral range of 610-660 nm. We observe that the average lifetime of NCs increases toward longer wavelengths as the number of in-film NCs increases. With the increased amount of NCs, the average lifetime increases even further and the emission of NCs is shifted further toward red. This is attributed to the enhanced nonradiative energy transfer between these NCs due to the inhomogeneous size distribution. Thus, in principle, for fine tuning of the collective color of NCs for color-conversion LEDs, it is important to control the energy transfer by changing the integrated number of NCs

High scotopic/photopic ratio white-light-emitting diodes integrated with semiconductor nanophosphors of colloidal quantum dots

Cataloged from PDF version of article.We propose and demonstrate single-chip white-light-emitting diodes (WLEDs) integrated with semiconductor nanophosphors of colloidal quantum dots for high scotopic/photopic (S/P) ratio. These color conversion WLEDs achieve S/P ratios over 3.00, which exceeds the current limit of 2.50 in common lighting technologies, while sustaining sufficient levels of color rendering index. (C) 2011 Optical Society of Americ

Color-converting combinations of nanocrystal emitters for warm-white light generation with high color rendering index

Cataloged from PDF version of article.Warm-white light emitting diodes with high color rendering indices are required for the widespread use of solid state lighting especially indoors. To meet these requirements, we propose and demonstrate warm-white hybrid light sources that incorporate the right color-converting combinations of CdSe/ZnS core-shell nanocrystals hybridized on InGaN/GaN LEDs for high color rendering index. Three sets of proof-of-concept devices are developed to generate high-quality warm-white light with (1) tristimulus coordinates (x,y)=(0.37,0.30), luminous efficacy (LE)=307 lm/W, color rending index (CR)=82.4, and correlated color temperature (CCT)=3228 K; (2) (x,y)=(0.38,0.31), LE=323 lm/W, CRI=81.0, and CCT=3190 K; and (3) (x,y)=(0.37,0.30), LE=303 lm/W, CRI=79.6, and CCT=1982 K

Quantum efficiency enhancement in nanocrystals using nonradiative energy transfer with optimized donor-acceptor ratio for hybrid LEDs

Cataloged from PDF version of article.The quantum efficiency enhancement in nanocrystal solids is critically important for their efficient use as luminophors on color-conversion light emitting diodes (LEDs). For this purpose, we investigate energy gradient mixture of nanocrystal solids for recycling their trapped excitons by varying their donor-acceptor nanocrystal ratios and study the resulting quantum efficiency enhancement as a function of the donor-acceptor ratio in the solid film for hybrid LEDs. We achieve a maximum quantum efficiency enhancement of 17% in these nanocrystal solids when the donor-acceptor ratio is 1:1, demonstrating their highly modified time-resolved photoluminescence decays to reveal the kinetics of strong energy transfer between them

Observation of efficient transfer from Mott-Wannier to Frenkel excitons in a hybrid semiconductor quantum dot-polymer composite at room temperature

Cataloged from PDF version of article.Efficient conversion from Mott-Wannier to Frenkel excitons is observed at room temperature. The time-resolved photoluminescence shows that the energy transfer rate and efficiency reach 0.262 ns-1 and 80.9%, respectively. The energy transfer is enabled by strong dipole-dipole coupling in a hybrid inorganic/organic system of CdSe/ZnS core/shell heteronanocrystal and poly[2-methoxy-5-(3,7-dimethyl-octyloxy)-1,4-phenylenevinylene] homopolymer composite, and the measured energy transfer efficiencies are consistent with the analytical model. © 2010 American Institute of Physics

Mechanisches Verhalten von zwei Titanaluminid Legierungen bei unterschiedlichen Temperaturen und Entwicklung einer neuen Methode zur Bestimmung der Spröd-Duktil-Übergangstemperatur

Titanaluminide auf der Basis von γ-TiAl sind vielversprechende Leichtbauwerkstoffe für den Einsatz in Hochtemperaturanwendungen aufgrund ihrer sehr guten massensspezifischen Eigenschaften. Aus diesem Grund ist es wichtig, das mechanische Verhalten dieser Legierungen bei höheren Temperaturen zu charakterisieren. Eine wichtige Eigenschaft dieser Werkstoffe ist der Spröd-Duktil-Übergang. Beim Spröd-Duktil-Übergang ändert sich das spröde Materialverhalten nach Überschreiten der Spröd-Duktil-Übergangstemperatur (BDTT, engl. Brittle-to-Ductile Transition Tempera-ture) hin zu duktilem Verhalten. Sowohl für die Herstellung als auch für die Auslegung ist es wichtig, die BDTT dieser Materialien zu kennen. Im Rahmen dieser Arbeit wird anhand der Legierung Ti-48Al-2Nb-0,7Cr-0,3Si eine Methode entwickelt, mit der die BDTT dieses Materials anhand einer Probe bestimmt werden kann. Damit können im Vergleich zu den konventionellen Methoden zur Ermittlung der BDTT Proben und Zeit gespart werden. Die neue Methode beruht auf dehnungskontrollierter zyklischer Belastung, die bei mehreren Temperaturen widerholt wird. Die Entwicklung der plastischen Dehnungsamplitude mit der Temperatur wird verwendet, um die BDTT des Werkstoffs zu ermitteln. Die BDTTs bei unterschiedlichen Dehnraten, die anhand dieser Methode ermittelt werden können, werden in dieser Arbeit mit den Ergebnissen aus der Literatur verglichen, wo die BDTTs mit konventionellen Methoden Zug- oder Biegeversuchen ermittelt wurden. Der Vergleich zeigt, dass die neu entwickelte Methode für Ti-48Al-2Nb-0,7Cr-0,3Si vergleichbare BDTTs liefert wie konventionelle Methoden, jedoch eben nur eine einzige Probe benötigt. Neben der Legierung Ti-48Al-2Nb-0,7Cr-0,3Si wird auch Ti-48Al-2Nb-2Cr mit der entwickelten Methode zur Bestimmung der BDTT untersucht. Um das mechanische Verformungsverhalten von Ti-48Al-2Nb-2Cr näher zu verstehen, werden außerdem Zug- und Wechselverformungsversuche bei unterschiedlichen Temperaturen und zwei Dehnraten sowie mikroskopische Untersuchungen an verformten Proben durchgeführt. Die BDTT ist in beiden Legierungen dehnratenabhängig und der Spröd-Duktil-Übergang findet durch Einsetzen der diffusionsunterstützten Versetzungsbewegung statt. Neben einem Spröd-Duktil-Übergang zeigen beide untersuchten Legierungen auch dynamische Reckalterung. Dabei diffundieren die Fremdatome schnell genug und bewegen sich während plastischer Verformung mit den Versetzungen zusammen und verankern diese bei ihrer Bewegung. Während dynamische Reckalterung in der Legierung Ti-48Al-2Nb-0,7Cr-0,3Si durch die Diffusion von O Atomen entsteht, kommt sie in der Legierung Ti-48Al-2Nb-2Cr durch die Diffusion von O und Cr Atomen zustande. Es zeigt sich, dass Spröd-Duktil-Übergang und dynamische Reckalterung aufgrund der Diffusion von Cr Atomen bei ungefähr gleichen Temperaturen einsetzen. Dies verhindert eine genaue Ermittlung der BDTT von Ti-48Al-2Nb-2Cr mit der entwickelten Methode

Computational study of power conversion and luminous efficiency performance for semiconductor quantum dot nanophosphors on light-emitting diodes

Cataloged from PDF version of article.We present power conversion efficiency (PCE) and luminous efficiency (LE) performance levels of high photometric quality white LEDs integrated with quantum dots (QDs) achieving an averaged color rendering index of >= 90 (with R9 at least 70), a luminous efficacy of optical radiation of >= 380 lm/W-opt a correlated color temperature of <= 4000 K, and a chromaticity difference dC <0.0054. We computationally find that the device LE levels of 100, 150, and 200 lm/W-elect can be achieved with QD quantum efficiency of 43%, 61%, and 80% in film, respectively, using state-of-the-art blue LED chips (81.3% PCE). Furthermore, our computational analyses suggest that QD-LEDs can be both photometrically and electrically more efficient than phosphor based LEDs when state-of-the-art QDs are used. (C) 2012 Optical Society of Americ