Mechanism of the operational effect of black spot growth in OLEDs

When organic light-emitting diodes (OLEDs) are exposed to the ambient atmosphere, water penetration through pinholes in the cathode results in the formation of non-emissive areas (black spots) due to local oxidation of the cathode around the pinhole. This degradation effect severely limits the lifetime of OLED devices and requires high performance encapsulation in order to delay its onset. We have investigated the process of degradation of OLED devices by water penetration through cathode pinholes, and have discovered that this is not just a simple oxidation of the cathode occurring as water diffuses within the device. We have observed that other layers within the device interact with the water. In solution processed OLEDs, the hole-injection layer (PEDOT:PSS) absorbs water due to the presence of the PSS acid (formation of H₃O⁺). This results in a slight local reduction of the luminance of the device (grey spot) around the pinhole location and actually a reduction of the cathode black spot growth rate at the pinhole during a shelf lifetime test. When the device is not operated, the PEDOT:PSS layer is acting as a local reservoir for water keeping it away from the cathode and slowing down the cathode degradation. However, when the device is operated, water that is captured by the PEDOT:PSS layer to form H₃O⁺ can be transported to the cathode under the influence of the applied electric field. This then increases the black spot growth rate. Experimental indications for this operational effect are provided by the threshold voltage behaviour of the effect and transient behaviour of the black spot growth after switching off the OLED. Direct evidence for the role of PEDOT:PSS in the operational effect has been provided by Raman Spectroscopy.     

Does volumetric absorptive microsampling eliminate the hematocrit bias for caffeine and paraxanthine in dried blood samples? A comparative study

Volumetric absorptive microsampling (VAMS) is a novel sampling technique that allows the straightforward collection of an accurate volume of blood (approximately 10 μL) from a drop or pool of blood by dipping an absorbent polymeric tip into it. The resulting blood microsample is dried and analyzed as a whole. The aim of this study was to evaluate the potential of VAMS to overcome the hematocrit bias, an important issue in the analysis of dried blood microsamples. An LC-MS/MS method for analysis of the model compounds caffeine and paraxanthine in VAMS samples was fully validated and fulfilled all pre-established criteria. In conjunction with previously validated procedures for dried blood spots (DBS) and blood, this allowed us to set up a meticulous comparative study in which both compounds were determined in over 80 corresponding VAMS, DBS and liquid whole blood samples. These originated from authentic human patient samples, covering a wide hematocrit range (0.21–0.50). By calculating the differences with reference whole blood concentrations, we found that analyte concentrations in VAMS samples were not affected by a bias that changed over the evaluated hematocrit range, in contrast to DBS results. However, VAMS concentrations tend to overestimate whole blood concentrations, as a consistent positive bias was observed. A different behavior of VAMS samples prepared from incurred and spiked blood, combined with a somewhat reduced recovery of caffeine and paraxanthine from VAMS tips at high hematocrit values, an effect that was not observed for DBS using a very similar extraction procedure, was found to be at the basis of the observed VAMS-whole blood deviations. Based on this study, being the first in which the validity and robustness of VAMS is evaluated by analyzing incurred human samples, it can be concluded that VAMS effectively assists in eliminating the effect of hematocrit.     

Nutzung verschiedener Auswerteverfahren für die Beurteilung der Aktivitätskonzentrierungen nach Inhalation in der Lunge

Für die Beurteilung einer Strahlenbelastung der Lunge nach Inhalation ist die Kenntnis des radioaktiven Stoffes sowie seine quantitative Verteilung von ausschlaggebender Bedeulung. Eine besonders geeignete Methode für den Nachweis der Radioaktivitāt bietet die Autoradioagraphie mikroskopischer Präparate. Es wird über Untersuchungsergebnisse nach Inhalation von ¹⁴⁴CeCl₃ bei Ratten und über Literaturergebnisse berichtet. Die Auswertung der Autoradiogramme reicht von der lichtmikroskopischen Beschreibung der Aktivitätsablagerung im Lungengewebe über die quantitative Auszählung von Aktivitäskonzentrierungen (hot spots) und der quantitativen Bestimmung der relativen Schwärzungen in Autoradiogrammen von Zellausstrichprāparaten bis hin zur Bestimmung der Aktivitätskonzentration in der Zelle. Sie führt bei α-Strahlen aussendenden Radionukliden darüber hinaus bis zur Identifizierungsmöglichkeit des inhalierten Radionuklids.

Eine besondere Bedeutung besitzt die Anwendung der Autoradiographie bei der Beurteilung von Bronchialsekreten nach innhalatorischer Aufnahme von radioaktiven Stoffen.     

Stable Sulfur Isotope Effects Related to Local Intense Sulfate Reduction in a Tidal Sandflat (Southern North Sea): Results from Loading Experiments

Abstract

Anoxic sediment surfaces coloured black by iron monosulfides (“black spots”) evolve in tidal sandflats of the Wadden Sea (southern North Sea) as a result of the degradation of buried organic matter. To follow the short- and long-term effects of organic matter burial on pore water and sediment isotopic biogeochemistry, formation of artificial black spots was initiated on the Groninger Plate (site RP63) in the backbarrier tidal flats of Spiekeroog island. Changes in concentrations (DOC, TA, TOC, sulfate, sulfide, TRS, Fe) and isotopic compositions (sulfate, sulfide, TRS, pyrite, TOC) were followed for up to 12 months and compared to reference areas. 13°C ratios of TOC clearly mirror the early diagenetic degradation of organic matter. At least temporarily closed system sulfate reduction is inferred for the artificial black spot from the variation of sulfate concentrations and stable sulfur isotope partitioning, In the interstitial waters of the black spot, 34S/32S values of coexisting dissolved sulfate and sulfide yield fractionation degrees between ?5 and ?25%. On the reference area, 34S/32S are fractionated by ?32 to ?42% as calculated from the isotope composition of solid phase reduced sulfur and pore water sulfate. Sulfur isotope fractionation seems to increase with decreasing sulfate reduction rate. Limiting factor seems to be the availability of DOC. Between the pyrite pool and the dissolved sulfide in the black spot, no significant isotope exchange is observed within 12 months.     

7A04铝合金产品黑斑原因分析

利用金相显微镜、扫描电镜和能谱仪,分析了7A04铝合金产品产生黑斑的原因.结果表明,化合物偏析和局部腐蚀是引起7A04铝合金产品产生黑斑的原因.     

同源双光路能见度仪的光斑提取算法研究

同源双光路能见度仪是一种基于数字摄像法的能见度仪,光斑提取算法是其能见度反演算法中的关键环节之一。从光斑成像的物理原理出发,提出了两种光斑提取算法。实验证明,即使没有图像预处理和数据后处理,其结果也和Vaisala LT31的结果具有很好的一致性。在确定上述两种方法中涉及的参数时,引入加权均方误差参量作为确定参数时的代价函数,该参量相对于其他参量有更好的效果,同时本参量还可以作为评价能见度结果的辅助指标。     

Analysis of Cannabinoids and Metabolites in Dried Urine Spots (DUS)

Dried urine spots (DUS) represent a potential alternative sample storage for forensic toxicological analysis. The aim of the current study was to develop and validate a liquid chromatographic tandem mass spectrometric procedure for the detection and quantitative determination of cannabinoids and metabolites in DUS. A two-step extraction was performed on DUS and urine samples. An LC-MS/MS system was operated in multiple reaction monitoring and positive polarization mode. The method was checked for sensitivity, specificity, linearity, accuracy, precision, recovery, matrix effects and carryover. The method was applied to 70 urine samples collected from healthy volunteers and drug addicts undergoing withdrawal treatment. The method was successfully developed for DUS. LODs lower than 2.0 ng/mL were obtained for all the monitored substances. All the validation parameters fulfilled the acceptance criteria either for DUS or urine. Among the real samples, 45 cases provided positive results for at least one compound. A good quali-quantitative agreement was obtained between DUS and urine. A good stability of THC, THCCOOH and THCCOOH-gluc was observed after a 24 h storage, in contrast to previously published results. DUS seems to provide a good alternative storage condition for urine that should be checked for the presence of cannabinoids and metabolites.     

Structure and properties of detonation waves of heterogeneous explosives from the point of view of the hot spots mechanism

It is assumed that the chemical reaction of a detonation transformation, that is, burning, arises first in separate hot spots originated by the explosive compression behind or within the detonation wave front due to heterogeneity of charges, instability of the detonation wave, etc. Then the burning spreads around into the bulk of the explosive and is completed in the Chapman–Jouguet plane, where the detonation product velocity relative to the detonation front is equal to the sound velocity. A simple analytical method proposed early by the authors is used to calculate the expression for the detonation transformation time, from which it follows that there are at least two nondimensional numbers defining the possibility of the realization of the mechanism mentioned above. The first one is the Frank-Kamenetskii number, that is, the relation of the characteristic time of the cooling of the hot spot to the adiabatic induction period at some characteristic temperature of the hot spot. The hot spot mechanism is realized if the Frank-Kamenetskii number is greater than the critical one that determines the minimum possible size of hot spots capable of ignition. The second number is the relation of the detonation transformation time in the presence of hot spots to the reaction time in accordance with classical mechanism. The hot spot mechanism at detonation is realized if this number is less than unity. By means of the numbers proposed, some interpretations of available experimental data concerning the detonation process are given.     

用全息分色法制作彩色全息图

通过使用三张编码全息片和三种滤光片,用白光将彩色正片的红、绿、兰三色信息记录在一张或两张全息片上。用单色激光同时再现出记录的三种颜色信息的光强分布,并将它们记录在同一张全息片上作成彩色全息图。本方法的显著优点是消除了影响彩色全息图质量的激光斑纹及提高了彩色全息图制作中的光功率利用率。