Ultranarrow Bandwidth Organic Photodiodes by Exchange Narrowing in Merocyanine H‐ and J‐Aggregate Excitonic Systems

Ultranarrowband organic photodiodes (OPDs) are demonstrated for thin film solid state materials composed of tightly packed dipolar merocyanine dyes. For these dyes the packing arrangement can be controlled by the bulkiness of the donor substituent, leading to either strong H‐ or strong J‐type exciton coupling in the interesting blue (H‐aggregate) and NIR (J‐aggregate) spectral ranges. Both bands are shown to arise from one single exciton band according to fluorescence measurements and are not just a mere consequence of different polymorphs within the same thin film. By fabrication of organic thin‐film transistors, these dyes are demonstrated to exhibit hole transport behavior in spin‐coated thin films. Moreover, when used as organic photodiodes in planar heterojunctions with C₆₀ fullerene, they show wavelength‐selective photocurrents in the solid state with maximum external quantum efficiencies of up to 11% and ultranarrow bandwidths down to 30 nm. Thereby, narrowing the linewidths of optoelectronic functional materials by exciton coupling provides a powerful approach to produce ultranarrowband organic photodiodes.     

可持续理念的体现——杭州来福士中心

正UNStudio由Ben van Berkel和Caroline Bos创立,是一个国际性的建筑设计网络。拥有三个全方位服务的国际事务所,分别位于阿姆斯特丹、香港和上海。专于建筑、室内建筑、产品设计、城市发展和基础设施项目。地址:浙江省杭州市钱江新城富春路业主方:凯德集团建筑面积:392526m~2项目年份:2017醒目的裙楼之上坐落着两座流线型的高楼,从中可以饱览钱塘江和西湖的迷人风光。     

Grouped Gaussian processes for solar power prediction

We consider multi-task regression models where the observations are assumed to be a linear combination of several latent node functions and weight functions, which are both drawn from Gaussian process priors. Driven by the problem of developing scalable methods for forecasting distributed solar and other renewable power generation, we propose coupled priors over groups of (node or weight) processes to exploit spatial dependence between functions. We estimate forecast models for solar power at multiple distributed sites and ground wind speed at multiple proximate weather stations. Our results show that our approach maintains or improves point-prediction accuracy relative to competing solar benchmarks and improves over wind forecast benchmark models on all measures. Our approach consistently dominates the equivalent model without coupled priors, achieving faster gains in forecast accuracy. At the same time our approach provides better quantification of predictive uncertainties.

     

The Next Generation of Colloidal Probes: A Universal Approach for Soft and Ultra‐Small Particles

The colloidal probe technique, which is based on the atomic force microscope, revolutionizes direct force measurements in many fields, such as interface science or biomechanics. It allows for the first time to determine interaction forces on the single particle or cell level. However, for many applications, important “blind spots” remain, namely, the possibility to probe interaction potentials for nanoparticles or complex colloids with a soft outer shell. Definitely, these are colloidal systems that are currently of major industrial importance and interest from theory. The here‐presented novel approach allows for overcome the aforementioned limitations. Its applicability has been demonstrated for 300 nm sized carboxylate‐modified latex particles as well as sub‐micron core–shell particles with a soft poly‐N‐isopropylacrylamide hydrogel shell and a rigid silica core. For the latter, which until now cannot be studied by the colloidal probe technique, determined is the temperature dependency of electrosteric and adhesion forces has been determined on the single particle level.     

Indoloazepinone‐Constrained Oligomers as Cell‐Penetrating and Blood–Brain‐Barrier‐Permeating Compounds

Non‐cationic and amphipathic indoloazepinone‐constrained (Aia) oligomers have been synthesized as new vectors for intracellular delivery. The conformational preferences of the [l ‐Aia‐Xxx]_n oligomers were investigated by circular dichroism (CD) and NMR spectroscopy. Whereas Boc‐[l ‐Aia‐Gly]_2,4‐OBn oligomers 12 and 13 and Boc‐[l ‐Aia‐β³‐h‐l ‐Ala]_2,4‐OBn oligomers 16 and 17 were totally or partially disordered, Boc‐[l ‐Aia‐l ‐Ala]₂‐OBn ( 14 ) induced a typical turn stabilized by C₅‐ and C₇‐membered H‐bond pseudo‐cycles and aromatic interactions. Boc‐[l ‐Aia‐l ‐Ala]₄‐OBn ( 15 ) exhibited a unique structure with remarkable T‐shaped π‐stacking interactions involving the indole rings of the four l ‐Aia residues forming a dense hydrophobic cluster. All of the proposed FITC‐6‐Ahx‐[l ‐Aia‐Xxx]₄‐NH₂ oligomers 19 – 23 , with the exception of FITC‐6‐Ahx‐[l ‐Aia‐Gly]₄‐NH₂ ( 18 ), were internalized by MDA‐MB‐231 cells with higher efficiency than the positive references penetratin and Arg₈. In parallel, the compounds of this series were successfully explored in an in vitro blood–brain barrier (BBB) permeation assay. Although no passive diffusion permeability was observed for any of the tested Ac‐[l ‐Aia‐Xxx]₄‐NH₂ oligomers in the PAMPA model, Ac‐[l ‐Aia‐l ‐Arg]₄‐NH₂ ( 26 ) showed significant permeation in the in vitro cell‐based human model of the BBB, suggesting an active mechanism of cell penetration.     

Phosphorus availability on many organically managed farms in Europe

Maintaining sufficient soil phosphorus (P) levels for non-limiting crop growth is challenging in organic systems since off-farm inputs of P are restricted. This study assessed the status of P on organic farms in Europe using soil test results for extractable P. Data was obtained from published literature, unpublished theses, and various national and regional databases of soil test values. Most of the data (15,506 observations) came from field scale soil tests, but in some cases (1272 observations) values had been averaged across a farm. Farm scale and field scale data were analysed separately and the impact of farm type (arable, dairy, grassland, horticulture, mixed, poultry, unknown) was assessed. Soil test results were assigned to P classes from very low (P class 1) to very high (P class 5). The farm scale data came primarily from Norway, Sweden and Switzerland and did not indicate deficiencies in extractable P; 93% of farms fell into class 3 or above. The majority of the field scale data came from Germany and indicated sufficient or higher levels of P availability for arable and grassland systems on 60% of fields; the remaining fields had low or very low available P. Adaptations in organic systems may improve P uptake and utilization efficiency allowing yields to be maintained in the short-term, nevertheless there is cause for concern about the long-term P sustainability of some organic farming systems in Europe. This highlights the need to reassess allowable P inputs in organic farming systems to improve overall sustainability.     

Discrimination of acoustic communication signals by grasshoppers (Chorthippus biguttulus): Temporal resolution, temporal integration, and the impact of intrinsic noise.

A characteristic feature of hearing systems is their ability to resolve both fast and subtle amplitude modulations of acoustic signals. This applies also to grasshoppers, which for mate identification rely mainly on the characteristic temporal patterns of their communication signals. Usually the signals arriving at a receiver are contaminated by various kinds of noise. In addition to extrinsic noise, intrinsic noise caused by stochastic processes within the nervous system contributes to making signal recognition a difficult task. The authors asked to what degree intrinsic noise affects temporal resolution and, particularly, the discrimination of similar acoustic signals. This study aims at exploring the neuronal basis for sexual selection, which depends on exploiting subtle differences between basically similar signals. Applying a metric, by which the similarities of spike trains can be assessed, the authors investigated how well the communication signals of different individuals of the same species could be discriminated and correctly classified based on the responses of auditory neurons. This spike train metric yields clues to the optimal temporal resolution with which spike trains should be evaluated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The traveling heads: multicenter brain imaging at 7 Tesla

Objective

This study evaluates the inter-site and intra-site reproducibility of 7 Tesla brain imaging and compares it to literature values for other field strengths.

Materials and methods

The same two subjects were imaged at eight different 7 T sites. MP2RAGE, TSE, TOF, SWI, EPI as well as B1 and B0 field maps were analyzed quantitatively to assess inter-site reproducibility. Intra-site reproducibility was measured with rescans at three sites.

Results

Quantitative measures of MP2RAGE scans showed high agreement. Inter-site and intra-site reproducibility errors were comparable to 1.5 and 3 T. Other sequences also showed high reproducibility between the sites, but differences were also revealed. The different RF coils used were the main source for systematic differences between the sites.

Conclusion

Our results show for the first time that multi-center brain imaging studies of the supratentorial brain can be performed at 7 T with high reproducibility and similar reliability as at 3T. This study develops the basis for future large-scale 7 T multi-site studies.

     

Electron microprobe and synchrotron x-ray fluorescence mapping of the heterogeneous distribution of copper in high-copper vineyard soils

The response of microorganisms to metal contamination of soils varies significantly from one investigation to another. One explanation is that metals are heterogeneously distributed at spatial scales relevant to microbes and that microoorganisms are able to avoid zones of intense contamination. This article aims to assess the microscale distribution of Cu in a vineyard soil. The spatial distribution of Cu was measured at two resolutions (0.3 mm and 20 microm) in thin sections of the surface 4 cm of undisturbed soil by electron microprobe and synchrotron X-ray microfluo-rescence spectroscopy. Bulk physicochemical analyses of Cu, pH, organic matter, texture, and mineralogy were performed. The results indicate that the Cu distribution is strongly heterogeneous at both scales of observation. Entire regions of the thin sections are virtually devoid of Cu, whereas highly localized "hotspots" have Cu signal intensities thousands of times higher than background. The distribution of Rb, or Al and Si, indicators of clay minerals, or Fe (iron (hydr)oxides), show that Cu is not preferentially associated with these mineral phases. Instead, Cu hotspots are associated with particulate organic matter. These observations suggest modification of current sampling protocols, and design of ecotoxicological experiments involving microorganisms, for contaminated soils.     

FEM simulation supported evaluation of a hydrogen grain boundary diffusion coefficient in MgH2

The diffusion coefficient data of hydrogen in the Magnesium-hydrogen system shows a large scatter, their trends extrapolations vary at room temperature between 10^?12 m²/s and 10^?29 m²/s. At room temperature the hydrogen diffusion coefficient in MgH₂ is, thus, uncertain by about 17 orders of magnitude. This may be partially attributed to grain boundaries contributing to the measured diffusion coefficient. In this paper we use finite-element (FEM) simulations to evaluate the influence of the grain boundary diffusion on the measured total diffusion depending on the difference of the grain boundary (D_GB) and volume (D_V) diffusion coefficients, as well as on the grain size. These results will be compared to Harrisson's analytical solutions. When the diffusion coefficients differ by more than D_V < 10^?3·D_GB, Harrison's diffusion regime C becomes the best way to describe the total diffusion. The results are used to re-interpret literature data on hydrogen diffusion in MgH₂ from this grain boundary contribution point of view. At 300 K, a hydrogen grain boundary diffusion coefficient ranging from D_GB = 10^?17 m²/s to D_GB = 10^?20 m²/s, depending on the individual type of sample in MgH₂, results from the data evaluation.