Characterization of GaN-based light-emitting diodes

Maximizing the performance of light-emitting diodes (LEDs) is essential for the widespread uptake of solid-state lighting. To contribute towards this goal, this thesis focuses on the electrical and optical characterization of InGaN/GaN-based multi quantum well LEDs. In this work a wide range of characterization methodologies are introduced. A new development is the study of the emission spectra under resonant optical pumping and varying electrical bias. This has proven to be useful to obtain insights into the carrier dynamics and is used here to investigate LED samples containing different numbers of quantum wells (QWs) with different thicknesses for the barriers. Despite having only small structural differences, these samples have shown strong differences in their performance, which are attributed to a stronger piezoelectric field in the QWs in the sample with thinner barriers. Fluorescence microscopy with selective excitation of the QWs also allows the study of the spatially dependent luminescent properties of LEDs. In this case ohmic contacts create an equipotential surface and influence the collective emission. Strong carrier escape is observed in photovoltaic mode under both open and short circuit conditions. To help identify the underlying recombination mechanisms, different voltage ideality factors are extracted and compared with each other. This thesis shows that the use of photovoltaic measurements together with biasdependent spectrally resolved luminescence is a powerful tool to investigate GaN LEDs. The methodologies presented here provide experimental tools to better understand carrier recombination processes in different LED samples. These methods can extended to samples grown on different crystallographic orientations or to study the effects of additional layers in novel LED structures

Nuevos datos sobre los acridoidea (Insecta: Orthoptera) del Pirineo y Prepirineo catalano-aragones

Hom presenta els resultats de les campanyes de recol•lecció realitzades el juliol de 1985 i 1986 a les zones pirenenca i pre-pirenenca de Girona, Osca i Lleida, que constitueixen la primera aportació al coneixement de l'acridofauna de la zona. Hom cita per segona vegada Omocestus antigai i 0. navasi.New data on the distribution of Acridoidea in Pyrenean and prepyrenean zones of Gerona, Huesca and Lerida provinces are presented. The material has been collected along july 1985 and july 1986. This paper is the first summarized work on acridological faune for the studied area. The presence of Omocestus antigai and 0. navasi is confirmed.Se presentan los resultados de las campanas acridológicas realizadas en julio de 1985 y 1986 en las zonas pirenaica y prepirenaica de las provincias de Gerona, Huesca y Lerida. Estos resultados constituyen la primera aportación de conjunto para el conocimiento de la acridofauna de la zona considerada. Se dan las segundas citas conocidas de las especies Omocestus antigai y 0. navasi

SLBN: A Scalable Max-min Fair Algorithm for Rate-Based Explicit Congestion Control

The growth of the Internet has increased the need for scalable congestion control mechanisms in high speed networks. In this context, we propose a rate-based explicit congestion control mechanism with which the sources are provided with the rate at which they can transmit. These rates are computed with a distributed max-min fair algorithm, SLBN. The novelty of SLBN is that it combines two interesting features not simultaneously present in existing proposals: scalability and fast convergence to the max-min fair rates, even under high session churn. SLBN is scalable because routers only maintain a constant amount of state information (only three integer variables per link) and only incur a constant amount of computation per protocol packet, independently of the number of sessions that cross the router. Additionally, SLBN does not require processing any data packet, and it converges independently of sessions' RTT. Finally, by design, the protocol is conservative when assigning rates, even in the presence of high churn, which helps preventing link overshoots in transient periods. We claim that, with all these features, our mechanism is a good candidate to be used in real deployments

Ensamblando datos. SIG y la historia humana del Valle de Oukaïmeden

Geographic Information Systems have become recently a methodological device to analyze the social configuration of historical landscapes. This paper deals with mobility and visibility as basic agents of the landscape organization, which is in turn, one of the theoretical bases of ARPA’s project. Hence, the need of applying these methodological tools to achieve a deeper knowledge of that process. GIS techniques show a direct connection between rock art or tumuli and the most efficient lines of movement, the best visibility orientations or the wet areas. Following Annales’ idea of Longue Durée, this paper traces the human process of modelling the Oukaïmeden landscape, from prehistoric times to more recent, historical ones, in which the control of critical resources and of mobility played a key role.Los sistemas de información geográfica han sido utilizados en los últimos años como herramienta metodológica a la hora de analizar la configuración social de los paisajes prehistóricos. En nuestro trabajo, y como una de las líneas teóricas de nuestro proyecto, entendemos la importancia de factores como la movilidad o la visibilidad dentro de esta configuración del paisaje. De ahí, la necesidad del uso de este tipo de herramientas metodológicas para comprender de una manera más profunda dicho proceso. La aplicación de los sistemas de información geográfica a la hora de analizar el arte rupestre y otra serie de elementos materiales prehistóricos, como los túmulos, parecen mostrarnos una relación directa entre dichas evidencias y factores tales como las líneas de movimiento, los condicionantes de visibilidad o las zonas de acumulación de pastos. De esta manera, y siguiendo la idea de la Longue Durée, hemos analizado la configuración del paisaje del valle de Oukaïmeden desde épocas prehistóricas hasta momentos más recientes, pudiendo entender como el control de los recursos y la movilidad, han sido factores determinantes en dicho proceso

A Replicative In Vitro Assay for Drug Discovery against Leishmania donovani.

The protozoan parasite Leishmania donovani is the causative agent of visceral leishmaniasis, a disease potentially fatal if not treated. Current available treatments have major limitations, and new and safer drugs are urgently needed. In recent years, advances in high-throughput screening technologies have enabled the screening of millions of compounds to identify new antileishmanial agents. However, most of the compounds identified in vitro did not translate their activities when tested in in vivo models, highlighting the need to develop more predictive in vitro assays. In the present work, we describe the development of a robust replicative, high-content, in vitro intracellular L. donovani assay. Horse serum was included in the assay media to replace standard fetal bovine serum, to completely eliminate the extracellular parasites derived from the infection process. A novel phenotypic in vitro infection model has been developed, complemented with the identification of the proliferation of intracellular amastigotes measured by EdU incorporation. In vitro and in vivo results for miltefosine, amphotericin B, and the selected compound 1 have been included to validate the assay

Unveiling the hidden entropy in ZnFe_2O_4

The antiferromagnetic (AFM) transition of the normal ZnFe_2O_4 has been intensively investigated with results showing a lack of long-range order, spin frustrations, and a "hidden" entropy in the calorimetric properties for inversion degrees delta approximate to 0 or delta = 0. As delta drastically impacts the magnetic properties, it is logical to question how a delta value slightly different from zero can affect the magnetic properties. In this work, (Zn_(1-delta)Fe_delta)[Zn_delta Fe_(2-delta)]O_4 with delta = 0.05 and delta = 0.27 have been investigated with calorimetry at different applied fields. It is shown that a delta value as small as 0.05 may affect 40% of the unit cells, which become locally ferrimagnetic (FiM) and coexists with AFM and spin disordered regions. The spin disorder disappears under an applied field of 1 T. Mossbauer spectroscopy confirms the presence of a volume fraction with a low hyperfine field that can be ascribed to these spin disordered regions. The volume fractions of the three magnetic phases estimated from entropy and hyperfine measurements are roughly coincident and correspond to approximately 1/3 for each of them. The "hidden" entropy is the zero point entropy different from 0. Consequently, the so-called "hidden" entropy can be ascribed to the frustrations of the spins at the interphase between the AFM-FiM phases due to having delta approximate to 0 instead of ideal delta = 0

Fortification and bioaccessibility of saffron apocarotenoids in potato tubers

Carotenoids are C40 isoprenoids with well-established roles in photosynthesis, pollination, photoprotection, and hormone biosynthesis. The enzymatic or ROS-induced cleavage of carotenoids generates a group of compounds named apocarotenoids, with an increasing interest by virtue of their metabolic, physiological, and ecological activities. Both classes are used industrially in a variety of fields as colorants, supplements, and bio-actives. Crocins and picrocrocin, two saffron apocarotenoids, are examples of high-value pigments utilized in the food, feed, and pharmaceutical industries. In this study, a unique construct was achieved, namely O6, which contains CsCCD2L, UGT74AD1, and UGT709G1 genes responsible for the biosynthesis of saffron apocarotenoids driven by a patatin promoter for the generation of potato tubers producing crocins and picrocrocin. Different tuber potatoes accumulated crocins and picrocrocin ranging from 19.41–360 to 105–800 μg/g DW, respectively, with crocetin, crocin 1 [(crocetin-(β-D-glucosyl)-ester)] and crocin 2 [(crocetin)-(β-D-glucosyl)-(β-D-glucosyl)-ester)] being the main compounds detected. The pattern of carotenoids and apocarotenoids were distinct between wild type and transgenic tubers and were related to changes in the expression of the pathway genes, especially from PSY2, CCD1, and CCD4. In addition, the engineered tubers showed higher antioxidant capacity, up to almost 4-fold more than the wild type, which is a promising sign for the potential health advantages of these lines. In order to better investigate these aspects, different cooking methods were applied, and each process displayed a significant impact on the retention of apocarotenoids. More in detail, the in vitro bioaccessibility of these metabolites was found to be higher in boiled potatoes (97.23%) compared to raw, baked, and fried ones (80.97, 78.96, and 76.18%, respectively). Overall, this work shows that potatoes can be engineered to accumulate saffron apocarotenoids that, when consumed, can potentially offer better health benefits. Moreover, the high bioaccessibility of these compounds revealed that potato is an excellent way to deliver crocins and picrocrocin, while also helping to improve its nutritional value

Performance evaluation of the high sensitive troponin I assay on the Atellica IM analyser

The Fourth Universal Definition of Myocardial Infarction Global Taskforce recommends the use of high sensitive troponin (hs-Tn) assays in the diagnosis of acute myocardial infarction. We evaluated the analytical performance of the Atellica IM High-sensitivity Troponin I Assay (hs-TnI) (Siemens Healthcare Diagnostics Inc., Tarrytown, USA) and compared its performance to other hs-TnI assays (Siemens Advia Centaur, Dimension Vista, Dimension EXL, and Abbott Architect (Wiesbaden, Germany)) at one or more sites across Europe. Precision, detection limit, linearity, method comparison, and interference studies were performed according to Clinical and Laboratory Standards Institute protocols. Values in 40 healthy individuals were compared to the manufacturer’s cut-offs. Sample turnaround time (TAT) was examined. Imprecision repeatability CVs were 1.1–4.7% and within-lab imprecision were 1.8–7.6% (10.0–25,000 ng/L). The limit of blank (LoB), detection (LoD), and quantitation (LoQ) aligned with the manufacturer’s values of 0.5 ng/L, 1.6 ng/L, and 2.5 ng/L, respectively. Passing-Bablok regression demonstrated good correlations between Atellica IM analyser with other systems; some minor deviations were observed. All results in healthy volunteers fell below the 99th percentile URL, and greater than 50% of each sex demonstrated values above the LoD. No interference was observed for biotin (≤ 1500 µg/L), but a slight bias at 5.0 g/L haemoglobin and 50 ng/L Tn was observed. TAT from was fast (mean time = 10.9 minutes) and reproducible (6%CV). Real-world analytical and TAT performance of the hs-TnI assay on the Atellica IM analyser make this assay fit for routine use in clinical laboratories