A comparison of consistent UV treatment versus inconsistent UV treatment in horticultural production of lettuce

UV radiation is an underrated radiation currently missing in many horticultural production systems of vegetables in protected cultivation. It can be added e.g., in LED light sources. Using lettuce as a model plant, this study determined whether the use of UVB LEDs is suitable (1) for use in consistent systems (indoor farming) or (2) inconsistent systems (greenhouse). Blue and red LEDs were selected as additional artificial lighting to UVB LEDs. Both approaches led to a reproducible increase of desired flavonol glycosides, such as quercetin-3-O-(6′′-O-malonyl)-glucoside or quercetin-3-O-glucuronide and the anthocyanin cyanidin-3-O-(6′′-O-malonyl)-glucoside in lettuce. The impact of the consistent UVB treatment is higher with up to tenfold changes than that of the inconsistent UVB treatment in the greenhouse. Varying natural light and temperature conditions in greenhouses might affect the efficiency of the artificial UVB treatment. Here, UVB LEDs have been tested and can be recommended for further development of lighting systems in indoor farming and greenhouse approaches

Comparison of Ultraviolet B Light‐Emitting Diodes with Single or Triple Quantum Wells

Light-emitting diodes (LEDs) with an emission wavelength of 310 nm containing either a single or a triple quantum well are compared regarding their efficiency and long-term stability. In addition, the influence of the thickness of the lower quantum well barrier and the quantum well thickness in single quantum well (SQW) LEDs is investigated. Electroluminescence measurements show a 28% higher initial output power for the SQW LEDs compared with the triple quantum well (TQW) LEDs because of larger spatial overlap of the carriers in the SQW as revealed by electro-optical simulations of the LED heterostructures. However, TQW LEDs show a higher output power than SQW LEDs after 1 h operation under harsh conditions. For SQW LEDs, it is found that for a thicker lower quantum well barrier (65 nm instead of 25 nm) the initial output power decreases by ≈15%. A thicker SQW (3 nm instead of 1.6 nm) reduces the initial output power by even 45% but increases the lifetime by a factor of 6 which is attributed to reduced Auger recombination from an enhanced spatial separation of electrons and holes in the quantum wells due to the quantum-confined Stark effect

Role of substrate quality on the performance of semipolar (11 2 - 2) InGaN light-emitting diodes

We compare the optical properties and device performance of unpackaged InGaN/GaN multiple-quantum-well light-emitting diodes (LEDs) emitting at ∼430 nm grown simultaneously on a high-cost small-size bulk semipolar (11 2 - 2) GaN substrate (Bulk-GaN) and a low-cost large-size (11 2 - 2) GaN template created on patterned (10 1 - 2) r-plane sapphire substrate (PSS-GaN). The Bulk-GaN substrate has the threading dislocation density (TDD) of ∼ and basal-plane stacking fault (BSF) density of 0 cm-1, while the PSS-GaN substrate has the TDD of ∼2 × 108cm-2 and BSF density of ∼1 × 103cm-1. Despite an enhanced light extraction efficiency, the LED grown on PSS-GaN has two-times lower internal quantum efficiency than the LED grown on Bulk-GaN as determined by photoluminescence measurements. The LED grown on PSS-GaN substrate also has about two-times lower output power compared to the LED grown on Bulk-GaN substrate. This lower output power was attributed to the higher TDD and BSF density

Skin tolerant inactivation of multiresistant pathogens using far-UVC LEDs

Multiresistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) cause serious postoperative infections. A skin tolerant far-UVC (< 240 nm) irradiation system for their inactivation is presented here. It uses UVC LEDs in combination with a spectral filter and provides a peak wavelength of 233 nm, with a full width at half maximum of 12 nm, and an irradiance of 44 µW/cm2. MRSA bacteria in different concentrations on blood agar plates were inactivated with irradiation doses in the range of 15–40 mJ/cm2. Porcine skin irradiated with a dose of 40 mJ/cm2 at 233 nm showed only 3.7% CPD and 2.3% 6-4PP DNA damage. Corresponding irradiation at 254 nm caused 11–14 times higher damage. Thus, the skin damage caused by the disinfectant doses is so small that it can be expected to be compensated by the skin's natural repair mechanisms. LED-based far-UVC lamps could therefore soon be used in everyday clinical practice to eradicate multiresistant pathogens directly on humans

A MicroRNA Next-Generation-Sequencing Discovery Assay (miND) for Genome-Scale Analysis and Absolute Quantitation of Circulating MicroRNA Biomarkers

The plasma levels of tissue-specific microRNAs can be used as diagnostic, disease severity and prognostic biomarkers for chronic and acute diseases and drug-induced injury. Thereby, the combination of diverse microRNAs into biomarker signatures using multivariate statistics seems especially powerful from the perspective of tissue and condition specific microRNA shedding into the plasma. Although next-generation sequencing (NGS) technology enables one to analyse circulating microRNAs on a genome-scale level, it suffers from potential biases (e.g., adapter ligation bias) and lacks absolute transcript quantitation as well as tailor-made quality controls. In order to develop a robust NGS discovery assay for genome-scale quantitation of circulating microRNAs, we first evaluated the sensitivity, repeatability and ligation bias of four commercially available small RNA library preparation protocols. The protocol from RealSeq Biosciences was selected based on its performance and usability and coupled with a novel panel of exogenous small RNA spike-in controls to enable quality control and absolute quantitation, thus ensuring comparability of data across independent NGS experiments. The established microRNA Next-Generation-Sequencing Discovery Assay (miND) was validated for its relative accuracy, precision, analytical measurement range and sequencing bias and was considered fit-for-purpose for microRNA biomarker discovery. Summarized, all these criteria were met, and thus, our analytical platform is considered fit-for-purpose for microRNA biomarker discovery from biofluids in the setting of any diagnostic, prognostic or patient stratification need. The established miND assay was tested on serum, cerebrospinal fluid (CSF), synovial fluid (SF) and extracellular vesicles (EV) extracted from cell culture medium of primary cells and proved its potential to be used across different sample types

Integrated Analyses of Microbiome and Longitudinal Metabolome Data Reveal Microbial-Host Interactions on Sulfur Metabolism in Parkinson's Disease.

Parkinson's disease (PD) exhibits systemic effects on the human metabolism, with emerging roles for the gut microbiome. Here, we integrate longitudinal metabolome data from 30 drug-naive, de novo PD patients and 30 matched controls with constraint-based modeling of gut microbial communities derived from an independent, drug-naive PD cohort, and prospective data from the general population. Our key results are (1) longitudinal trajectory of metabolites associated with the interconversion of methionine and cysteine via cystathionine differed between PD patients and controls; (2) dopaminergic medication showed strong lipidomic signatures; (3) taurine-conjugated bile acids correlated with the severity of motor symptoms, while low levels of sulfated taurolithocholate were associated with PD incidence in the general population; and (4) computational modeling predicted changes in sulfur metabolism, driven by A. muciniphila and B. wadsworthia, which is consistent with the changed metabolome. The multi-omics integration reveals PD-specific patterns in microbial-host sulfur co-metabolism that may contribute to PD severity

The 2020 UV emitter roadmap

Solid state UV emitters have many advantages over conventional UV sources. The (Al,In,Ga)N material system is best suited to produce LEDs and laser diodes from 400 nm down to 210 nm—due to its large and tuneable direct band gap, n- and p-doping capability up to the largest bandgap material AlN and a growth and fabrication technology compatible with the current visible InGaN-based LED production. However AlGaN based UV-emitters still suffer from numerous challenges compared to their visible counterparts that become most obvious by consideration of their light output power, operation voltage and long term stability. Most of these challenges are related to the large bandgap of the materials. However, the development since the first realization of UV electroluminescence in the 1970s shows that an improvement in understanding and technology allows the performance of UV emitters to be pushed far beyond the current state. One example is the very recent realization of edge emitting laser diodes emitting in the UVC at 271.8 nm and in the UVB spectral range at 298 nm. This roadmap summarizes the current state of the art for the most important aspects of UV emitters, their challenges and provides an outlook for future developments

A community effort in SARS-CoV-2 drug discovery.

peer reviewedThe COVID-19 pandemic continues to pose a substantial threat to human lives and is likely to do so for years to come. Despite the availability of vaccines, searching for efficient small-molecule drugs that are widely available, including in low- and middle-income countries, is an ongoing challenge. In this work, we report the results of an open science community effort, the "Billion molecules against Covid-19 challenge", to identify small-molecule inhibitors against SARS-CoV-2 or relevant human receptors. Participating teams used a wide variety of computational methods to screen a minimum of 1 billion virtual molecules against 6 protein targets. Overall, 31 teams participated, and they suggested a total of 639,024 molecules, which were subsequently ranked to find 'consensus compounds'. The organizing team coordinated with various contract research organizations (CROs) and collaborating institutions to synthesize and test 878 compounds for biological activity against proteases (Nsp5, Nsp3, TMPRSS2), nucleocapsid N, RdRP (only the Nsp12 domain), and (alpha) spike protein S. Overall, 27 compounds with weak inhibition/binding were experimentally identified by binding-, cleavage-, and/or viral suppression assays and are presented here. Open science approaches such as the one presented here contribute to the knowledge base of future drug discovery efforts in finding better SARS-CoV-2 treatments.R-AGR-3826 - COVID19-14715687-CovScreen (01/06/2020 - 31/01/2021) - GLAAB Enric

Investigation of the degradation behavior of InAlGaN-based ultraviolet light-emitting diodes to improve their reliability

Zentraler Bestandteil dieser Arbeit ist die Untersuchung des Degradationsverhaltens von ultravioletten (UV) Leuchtdioden (LEDs), die im UV-C (200 nm bis 280 nm) und UV-B (280 nm bis 340 nm) Spektralbereich emittieren. Als Degradationsverhalten ist dabei die Änderung von elektrooptischen Parametern, wie beispielsweise der optischen Leistung oder der Strom-Spannungskennlinie im Betrieb bei konstantem Betriebsstrom und konstanter Temperatur definiert. Um die Lebensdauer der LEDs zu verlängern werden die Heterostruktur um den pn-Übergang und das Verfahren zur Aktivierung der p-Dotierung gezielt variiert. Zusammengefasst wurden drei Degradationsmechanismen identifiziert: Der erste Degradationsmechanismus wird eindeutig dem p-Gebiet zugeordnet und kann durch eine Aktivierung von Magnesium-Wasserstoff-Defektkomplexen beschrieben werden. In der p-Seite kommt es zu einer Zunahme der p-Leitfähigkeit, einer Abnahme der Schottky-Barriere am p-Kontakt und einer Zunahme der Lochinjektionseffizienz. Aufgrund dieses Mechanismus kann in den ersten Betriebsstunden bei einigen LEDs eine Zunahme der optischen Leistung, Abnahme der Betriebsspannung und Zunahme der Kapazität der Raumladungszone am p-Kontakt beobachtet werden. Degradationsmechanismus 2 basiert auf einer Zunahme von Punktdefekten in und um die aktive Zone, wobei es wahrscheinlich im Betrieb der LEDs zu einer Aktivierung von Magnesium oder Vakanzen aus wasserstoffbeinhaltenden Defektkomplexen kommt. Diese Defekte können beispielweise als Zentren für nichtstrahlende Rekombination wirken. Die untersuchten LEDs zeigen hierbei eine schnelle Abnahme der optischen Leistung und eine schnelle Zunahme des Stroms unterhalb der Einschaltspannung in den ersten ~100 h Betrieb. Zudem fungieren diese Defekte als Akzeptoren und kompensieren die n-Dotierung, was zu einer Zunahme der Betriebsspannung im gleichen Zeitraum führt. Durch Messungen der Konzentration von Wasserstoffverunreinigungen an ungealterten und gealterten LEDs kann nachgewiesen werden, dass die Degradationsmechanismen 1 und 2 mit dem Aufbrechen von H-beinhaltenden Defektkomplexen und der Freisetzung von H-Atomen zusammenhängt. Es zeigt sich, dass die H-Konzentration in der p-Seite und in der aktiven Zone in den ersten ~10 h um ein bis zwei Größenordnungen abnimmt und die freigesetzten H-Atome in die n-Seite migrieren. Dabei wird die Abnahme der H-Konzentration und optischen Leistung in den ersten Betriebsstunden stark von der Stromdichte, aber nur geringfügig von der Temperatur beeinflusst. Degradationsmechanismus 3 kann durch Diffusion von Punktdefekten in und um die aktive Zone physikalisch erklärt werden. Die Zunahme der Konzentration von Punktdefekten führt wiederum zu einer Abnahme der optischen Leistung. Ein Indiz für den Diffusionsprozess ist die Beobachtung, dass die Änderung der optischen Leistung der untersuchten LEDs für Betriebszeiten >100 h eine Abhängigkeit von der Wurzel der Betriebszeit zeigt. Zudem zeigte sich, dass Degradationsmechanismus 3 von der Stromdichte und der Temperatur angetrieben wird und somit vermutlich kein reiner Diffusionsprozess ist. Um die Lebensdauer der Bauelemente zu verlängern, wurden basierend auf diesen Erkenntnissen das Heterostrukturdesign, das p-Dotierprofil und das Schema der p-Aktivierung von UV-B LEDs mit Emission bei ~310 nm variiert. Zusammengefasst deuten die Ergebnisse an, dass eine Verbesserung der Lochinjektion in die aktive Zone zu einer Zunahme der initialen optischen Leistung und einer Verlängerung der Lebensdauer der UV-B LEDs führt. Beispielsweise führt die Optimierung des Designs der Elektronenblockierschicht, im Hinblick auf die Zunahme der Lochinjektion, zu einer signifikanten Zunahme der optischen Leistung und Lebensdauer der LEDs. Folglich führt das ausgeglichenere Elektronen-zu-Löcher-Verhältnis in der aktiven Zone zu einer Zunahme der strahlenden Rekombination und reduziert die Wahrscheinlichkeit von Auger-Rekombination, welche wiederum für die Generation heißer Ladungsträger verantwortlich ist. Durch Kombination all dieser optimierenden Maßnahmen konnten UV-B LEDs realisiert werden, die eine L70 Lebensdauer von ≥20.000 h haben, was der Lebensdauer von modernen blauen und violetten LEDs nahe kommt.The main focus of this thesis is the investigation of the degradation behavior of ultraviolet (UV) light-emitting diodes (LEDs) emitting in the UV-C (200 nm to 280 nm) and UV-B (280 nm to 340 nm) spectral regions. The degradation behavior is defined as the change in the electro-optical characteristics of the LED, such as the optical power or the current-voltage characteristics, during constant current and temperature operation. In order to increase the lifetime of the LEDs, the heterostructure design of the active region and the p-activation procedure has been optimized. Three different physical degradation mechanisms have been identified: The first degradation mechanism occurs in the p-layers and can be attributed to an operation induced activation of magnesium-hydrogen defect complexes. This leads to an increase in the p-conductivity, a reduction in the Schottky-barrier at the p-contact and an increase in the hole injection efficiency. An increase in the optical power, a reduction in the drive voltage and an increase in the capacitance of the space-charge region, at the p-contact, can be observed in the first hours of operation, due to this degradation mechanism. Degradation mechanism 2 describes an increase in the point defect density in or around the active region, most likely due to an operation induced activation of Magnesium or vacancies from hydrogen-containing defect complexes. These defects can, for example, act as centers for non-radiative recombination. As a consequence, a fast reduction in the optical power and a fast increase in the current below the turn-on voltage, within the first ~100 h of operation, can be observed in the LEDs under investigation. Furthermore, these defects act as acceptor states and compensate the intended n-doping which leads to an increase in the operation voltage in the same operation time period. The hypothesis that degradation mechanisms 1 and 2 can be related to the breakup of H-containing defect complexes and dissociation of H-atoms, has been proven by measurements of the H-concentration in unaged and aged LEDs. The H-concentration reduces in the p-side and in the active region during the first ~10 h of operation by two orders of magnitude and the dissociated H-atoms migrate into the n-side. The observed reduction in the H-concentration and the reduction in the optical power during the first hours of operation are strongly influenced by the current density, but only slightly by temperature. A diffusion of point defects in and around the active region is the probable physical explanation responsible for degradation mechanism 3. The increase in the point defect concentration leads to a reduction in the optical power. Furthermore, the reduction in the optical power for operation times >100 h follows a square root time dependence, which confirms that a diffusion process is most likely involved in the degradation. In addition, degradation mechanism 3 is driven not only by the temperature but also by the current density, which leads to the conclusion that another physical process, in addition to diffusion, is responsible for the degradation. Based on these findings, the heterostructure design, profile of the p-doping and the procedure for the p-activation of UV-B LEDs, with emission at ~310 nm, have been varied and their influence on the lifetime of the devices has been investigated. The impact, of these parameters, on the initial electro-optical characteristics of the LEDs has always been considered. In summary, the results indicate a strong impact of the hole injection efficiency, into the active region, on the initial optical power and lifetime of the UV-B LEDs. For example, by optimizing the design of the electro-blocking-layer for increased hole injection, the lifetime and optical power of the LEDs can be significantly increased. As a consequence, a balanced electron-hole-ratio in the active region increases the radiative recombination efficiency and reduces the probability of Auger-recombination, which is responsible for the generation of hot carriers. By combining all these optimizations UV-B LEDs have been realized with a L70 lifetime of ≥20.000 h, which is comparable to the lifetime of state-of-the-art violet and blue LEDs.BMBF, 03ZZ0106A, Zwanzig20 - Advenced UV-C EpitaxieBMBF, 03ZZ0130A, Zwanzig20 - Advanced UV for Life - ZuvUVBMWi, 03EFCBE067, EXIST-Forschungstransfer: Entwicklung kommerziell verwertbarer UV-B LEDsDFG, SFB 787, Semiconductor NanoPhotonics: Materials, Models, Device