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Large-area (50 cm2) two-dimensionally periodic crystalline silicon structures with lattice constants between 350 nm and 2 µm were prepared by high-rate electron-beam evaporation of silicon on nanoimprinted glass substrates. All processing steps have little technological intricacy, are up-scalable to large areas, and thus hold the potential for low-cost production of advanced nanostructured photovoltaic devices or large-area 2D photonic crystals. The 2 µm-periodic materials exhibit a promising absorption enhancement with light path enhancement factors larger 40 at λ=1000 nm enabling the development of highly effective light trapping architectures for polycrystalline silicon thin-film solar cells. Photonic band structure effects at near infrared wavelengths could be identified by angular resolved reflection measurements in hexagonal 350nm-periodically patterned silicon films inspiring the formation of large-area two-dimensional photonic crystals for telecommunication wavelengths. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Background: People with dementia are often inapproachable due to symptoms of their illness. Therefore nurses should establish relationships with dementia patients via their remaining resources and facilitate communication. In order to achieve this, different targeted non-pharmacological interventions are recommended and practiced. However there is no sufficient evidence about the efficacy of most of these interventions. A number of publications highlight the urgent need for methodological sound studies so that more robust conclusions may be drawn. Methods/Design: The trial is designed as a cluster randomized controlled trial with 20 nursing homes in Saxony and Saxony-Anhalt (Germany) as the units of randomization. Nursing homes will be randomly allocated into 4 study groups consisting of 5 clusters and 90 residents: snoezelen, structured reminiscence therapy, 10-minutes activation or unstructured verbal communication (control group). The purpose is to determine whether the interventions are effective to reduce apathy in long-term care residents with dementia (N = 360) as the main outcome measure. Assessments will be done at baseline, 3, 6 and 12 months after beginning of the interventions. Discussion: This trial will particularly contribute to the evidence on efficacy of non-pharmacological interventions in dementia care. Trial Registration: ClinicalTrials.gov NCT00653731 [ABSTRACT FROM AUTHOR]

In this study, grazing‐incidence small‐angle X‐ray scattering (GISAXS) is used to collect statistical information on dimensional parameters in an area of 20 × 15 mm on photonic structures produced by nanoimprint lithography. The photonic structures are composed of crystalline and locally quasicrystalline two‐dimensional patterns with structure sizes between about 100 nm and 10 µm to enable broadband visible light absorption for use in solar‐energy harvesting. These first GISAXS measurements on locally quasicrystalline samples demonstrate that GISAXS is capable of showing the locally quasicrystalline nature of the samples while at the same time revealing the long‐range periodicity introduced by the lattice design. The scattering is described qualitatively in the framework of the distorted‐wave Born approximation using a hierarchical model mirroring the sample design, which consists of a rectangular and locally quasicrystalline supercell that is repeated periodically to fill the whole surface. The nanoimprinted samples are compared with a sample manufactured using electron‐beam lithography and the distortions of the periodic and locally quasiperiodic samples are quantified statistically. Owing to the high sensitivity of GISAXS to deviations from the perfect lattice, the misalignment of the crystallographic axes was measured with a resolution of 0.015°, showing distortions of up to ±0.15° in the investigated samples. Grazing‐incidence small‐angle X‐ray scattering (GISAXS) is used to examine crystalline and locally quasicrystalline 2D photonic structures produced by nanoimprint lithography for photovoltaic applications. Using a hierarchical theoretical description, lattice distortions are quantified from the GISAXS measurements, showing the differences in reproduction quality between the investigated samples. [ABSTRACT FROM AUTHOR]

Functional inactivation of HFE or hemojuvelin ( HJV) is causatively linked to adult or juvenile hereditary hemochromatosis, respectively. Systemic iron overload results from inadequate expression of hepcidin, the iron regulatory hormone. While HJV regulates hepcidin by amplifying bone morphogenetic protein (BMP) signaling, the role of HFE in the hepcidin pathway remains incompletely understood. We investigated the pathophysiological implications of combined Hfe and Hjv ablation in mice. Isogenic Hfe/ and Hjv/ mice were crossed to generate double Hfe/ Hjv/ progeny. Wild-type control and mutant mice of all genotypes were analyzed for serum, hepatic, and splenic iron content, expression of iron metabolism proteins, and expression of hepcidin and Smad signaling in the liver, in response to a standard or an iron-enriched diet. As expected, Hfe/ and Hjv/ mice developed relatively mild or severe iron overload, respectively, which corresponded to the degree of hepcidin inhibition. The double Hfe/ Hjv/ mice exhibited an indistinguishable phenotype to single Hjv/ counterparts with regard to suppression of hepcidin, serum and hepatic iron overload, splenic iron deficiency, tissue iron metabolism, and Smad signaling, under both dietary regimens. We conclude that the hemochromatotic phenotype caused by disruption of Hjv is not further aggravated by combined Hfe/ Hjv deficiency. Our results provide genetic evidence that Hfe and Hjv operate in the same pathway for the regulation of hepcidin expression and iron metabolism. Key messages: [ABSTRACT FROM AUTHOR]

Radial junction solar cells with only ~100 nm thin amorphous Si absorber layer deposited on Si nanowires can be prepared by a relatively simple and low-cost thin film technology. Metal assisted Si nanowire growth leads to a disorder in nanowire orientations, lengths and shapes, which is then preserved by the conformal absorber layer. Interestingly, high conversion efficiencies are reached in spite of the disorder. In this contribution we describe microscopic methods aiming at exploring the role of structural disorder on the local electronic properties of radial junction cells. A method for locating the same nanostructure in different microscopes, using the nanoindentation marks for orientation on the sample, is described. Indents can be easily located by optical microscopy, scanning electron microscopes or scanning probe microscopes. Groups of three indents arranged in triangles can serve as coordinate systems for triangulation on samples, enabling correlative microscopy even in instruments which were not designed for it. This approach also enables localization of the same positions on samples after repeated mounting in various microscopes with a precision better than 50 nm. This is possible even on samples without any structural features, as demonstrated for flat silicon thin films prepared by solid phase crystallization, for which we have correlated crystallographic maps from electron backscattering diffraction and conductivity maps by atomic force microscopy. The technique allows observing the same locations before and after technological steps, as shown for the hot wire chemical vapor deposition of carbon nanowalls. [ABSTRACT FROM AUTHOR]

Abstract: We present a comprehensive theoretical analysis accompanying our experimental development of micro-structured thin film polycrystalline silicon solar cell absorbers. Our focus is on 2D-periodic arrays of holes which do not act as a superficial scattering grating but pierce the entire silicon absorber layer. We deviate from the commonly used model of vertical hole sidewalls by employing conical frustum shaped holes with a range of opening angles. Additionally, an experimentally motivated front texture is applied to the simulated solar cell absorbers and varied in texture aspect. Based on this parametric absorber model, for a single domain period of , we discuss light trapping and optical losses in thin film cells with absorptive front and back contacts and a perfectly transparent glass encapsulation layer. Implications from this study are that light trapping in square periodic arrays with periods larger than the wavelength of light can be enhanced by microholes but that it cannot replace a front texture which provides both antireflection and scattering. [Copyright &y& Elsevier]

The objective was to explore how ferritin-H deletion influences 59Fe-distribution and excretion-kinetics in mice. Kinetics of 59Fe-release from organs, whole-body excretion, and distribution-kinetics of intravenously injected 59Fe trace amounts were compared in iron-deficient and iron-replete mice with (FthΔ/Δ) and without (Fth lox/lox ) conditional Mx-Cre-induced ferritin-H deletion. 59Fe was released from spleen and liver beginning on day 2 and day 5 after ferritin-H deletion, respectively, but was not excreted from the body. Plasma-59Fe was cleared significantly faster in iron-deficient FthΔ/Δ-mice than in iron-adequate Fth lox/lox -controls. 59Fe-distribution showed a transient peak (e.g., in heart, kidney, muscle) in Fth lox/lox control mice, but not in ferritin-H–deleted FthΔ/Δ mice 24 hours after 59Fe injection. 59Fe uptake into the liver and spleen was significantly lower in iron-deficient FthΔ/Δ than in Fth lox/lox mice 24 hours and 7 days after injection, respectively, and rapidly appeared in circulating erythrocytes instead. The rate of 59Fe release after ferritin-H deletion supports earlier data on ferritin turnover in mammals; released 59Fe is not excreted from the body. Instead, 59Fe is channeled into erythropoiesis and circulating erythrocytes significantly more extensively and faster. Along with a lack of transient interim 59Fe storage (e.g., in the heart and kidney), this finding is evidence for ferritin-related iron storage-capacity affecting rate and extent of iron utilization. [Copyright &y& Elsevier]

Abstract: The fabrication of light trapping architectures for electron beam (e-beam) evaporated polycrystalline Si thin film solar cells is investigated based on tailored self-organized light scattering silica nanospheres and 2 dimensional periodic nanoimprinted structures on glass. A microscopic analysis reveals a unique correlation between the microstructure of high-rate e-beam evaporated Si and the substrate topography. These features provide the basis for the design of nanostructured Si that complies with its distinctive growth characteristics. A layer of self-organized nanospheres embedded in a sol–gel matrix and an anti-reflection coating is found to be an e-beam compatible light trapping approach for poly-Si solar cells, contributing to an increase of 50% in current collection. We developed a preparation process for arrays of equidistant free-standing Si crystals with remarkable optical absorption characteristics based on a nanoimprinted glass substrate by selectively etching e-beam evaporated Si. This periodic approach opens design possibilities for effective three-dimensional architectures for advanced photon management. [Copyright &y& Elsevier]

Multi-junction photovoltaics approaches are being explored to mitigate thermalization losses that occur in the absorption of high-energy photons. However, the design of tandem cells faces challenges such as light reflection and parasitic absorption. Nanostructures have emerged as promising solutions due to their anti-reflection properties, which enhances light absorption. III-V nanowires (NWs) solar cells can achieve strong power conversion efficiencies, offering the advantage of potentially integrating tunnel diodes within the same fabrication process. Metal halide perovskites (MHPs) have gained attention for their optoelectronic attributes and cost-effectiveness. Notably, both material classes allow for tunable bandgaps. This study explores the integration of MHPs with III-V NWs solar cells in both two-terminal and three-terminal configurations. Our primary focus lies in the optical analysis of a tandem design using III-V semiconductor nanowire arrays in combination with perovskites, highlighting their potential for tandem applications. The space offered by the compact footprint of NW arrays is used in an interpenetrated tandem structure. We systematically optimize the bottom cell, addressing reflectivity and parasitic absorption, and extend to a full tandem structure, considering experimentally feasible thicknesses. Simulation of a three-terminal structure highlights a potential increase in efficiency, decoupling the operating points of the subcells. The two-terminal analysis underscores the benefits of nanowires in reducing reflection and achieving a higher matched current between the top and the bottom cells. This research provides significant insights into NW tandem solar cell optics, enhancing our understanding of their potential to improve photovoltaic performance.

Perovskite-silicon tandem solar cells offer the possibility of overcoming the power conversion efficiency limit of conventional silicon solar cells. Various textured tandem devices have been presented aiming at improved optical performance, but optimizing film growth on surface-textured wafers remains challenging. Here we present perovskite-silicon tandem solar cells with periodic nanotextures that offer various advantages without compromising the material quality of solution-processed perovskite layers. We show a reduction in reflection losses in comparison to planar tandems, with the new devices being less sensitive to deviations from optimum layer thicknesses. The nanotextures also enable a greatly increased fabrication yield from 50% to 95%. Moreover, the open-circuit voltage is improved by 15 mV due to the enhanced optoelectronic properties of the perovskite top cell. Our optically advanced rear reflector with a dielectric buffer layer results in reduced parasitic absorption at near-infrared wavelengths. As a result, we demonstrate a certified power conversion efficiency of 29.80%., (© 2022. The Author(s).)

Despite a wide array of applications, deep ultra-violet light emitting diodes offer relatively poor efficiencies compared to their optical counterparts. A contributing factor is the lower light extraction efficiency due to both highly absorbing p-contacts and total internal reflection. Here, we propose a structure consisting of a hexagonal periodic array of cylindrical nanoholes in the multi-layered p-contact which are filled with platinum. This nanostructure reduces the absorption of the p-contact layer, leading to a higher emission into the n-contact compared to a planar reference. An optimum geometry of the nanostructure allows a light extraction efficiency of 15.0%, much higher than the typical 4.6% of a planar reference. While the nanostructure strongly decreases the light absorption in the p-contact, it is still not able to considerably reduce the total internal reflection. Consequently, the nanostructured p-contact should be combined with other optical strategies, such as nanopatterned sapphire substrates to increase the efficiency even further. Despite this, the nanostructure described in this work provides a readily realizable path to enhancing the light extraction efficiency of state-of-the-art deep ultra-violet light emitting diodes., (© 2022. The Author(s).)

Multi-junction solar cells allow to utilize sunlight more effectively than single junction solar cells. In this work, we present optical simulations of III-V-on-silicon solar cells with a metal grating at the back, which experimentally have reached more than 33% power conversion efficiency. First, we perform simulations with the finite element method and compare them with experimental data to validate our model. We find that accurately modeling the investigated geometrical structure is necessary for best agreement between simulation and experimental measurements. Then, we optimize the grating for maximized light trapping using a computationally efficient Bayesian optimization algorithm. The photo current density of the limiting silicon bottom cell is improved from 13.48 mA/cm 2 for the experimental grating to 13.85 mA/cm 2 for the optimized metal grating. Investigation of all geometrical optimization parameters of the grating (period, height,…) shows that the structure is most sensitive towards the period, a parameter highly controllable in manufacturing by inference lithography. The results show a pathway to exceed the current world record efficiency of the III-V-on-silicon solar cell technology.

Large-scale nanoimprinted metasurfaces based on silicon photonic crystal slabs were produced and coated with a NaYF 4 :Yb 3+ /Er 3+ upconversion nanoparticle (UCNP) layer. UCNPs on these metasurfaces yield a more than 500-fold enhanced upconversion emission compared to UCNPs on planar surfaces. It is also demonstrated how the optical response of the UCNPs can be used to estimate the local field energy in the coating layer. Optical simulations using the finite element method validate the experimental results and the calculated spatial three-dimensional field energy distribution helps us to understand the emission enhancement mechanism of the UCNPs closely attached to the metasurface. In addition, we analyzed the spectral shifts of the resonances for uncoated and coated metasurfaces and metasurfaces submerged in water to enable a prediction of the optimum layer thicknesses for different excitation wavelengths, paving the way to applications such as electromagnetic field sensors or bioassays.

We present a detailed illumination model for bifacial photovoltaic modules in a large PV field. The model considers direct light and diffuse light from the sky and treats the illumination of the ground in detail, where it discriminates between illumination of the ground arising from diffuse and direct light. The model calculates the irradiance components on arbitrarily many positions along the module. This is relevant for finding the minimal irradiance, which determines the PV module performance for many PV modules. Finally, we discuss several examples. The code for the model is available online (DOI: 10.5281/zenodo.3543570).

Light emitting diodes (LEDs) in the deep ultra-violet (DUV) offer new perspectives for multiple applications ranging from 3D printing to sterilization. However, insufficient light extraction severely limits their efficiency. Nanostructured sapphire substrates in aluminum nitride based LED devices have recently shown to improve crystal growth properties, while their impact on light extraction has not been fully verified. We present a model for understanding the impact of nanostructures on the light extraction capability of DUV-LEDs. The model assumes an isotropic light source in the semiconductor layer stack and combines rigorously computed scattering matrices with a multilayer solver. We find that the optical benefit of using a nanopatterned as opposed to a planar sapphire substrate to be negligible, if parasitic absorption in the p-side of the LED is dominant. If losses in the p-side are reduced to 20%, then for a wavelength of 265 nm an increase of light extraction efficiency from 7.8% to 25.0% is possible due to nanostructuring. We introduce a concept using a diffuse ('Lambertian') reflector as p-contact, further increasing the light extraction efficiency to 34.2%. The results underline that transparent p-sides and reflective p-contacts in DUV-LEDs are indispensable for enhanced light extraction regardless of the interface texture between semiconductor and sapphire substrate. The optical design guidelines presented in this study will accelerate the development of high-efficiency DUV-LEDs. The model can be extended to other multilayer opto-electronic nanostructured devices such as photovoltaics or photodetectors.

The optical response of periodically nanotextured layer stacks with dimensions comparable to the wavelength of the incident light can be computed with rigorous Maxwell solvers, such as the finite element method (FEM). Experimentally, such layer stacks are often prepared on glass superstrates with a thickness, which is orders of magnitude larger than the wavelength. For many applications, light in these thick superstrates can be treated incoherently. The front side of thick superstrate is located far away from the computational domain of the Maxwell solvers. Nonetheless, it has to be considered in order to achieve accurate results. In this contribution, we discuss how solutions of rigorous Maxwell solvers can be corrected for flat front sides of the superstrates with an incoherent a posteriori approach. We test these corrections for hexagonal sinusoidal nanotextured silica-silicon interfaces, which are applied in certain silicon thin-film solar cells. These corrections are determined via a scattering matrix, which contains the full scattering information of the periodically nanotextured structure. A comparison with experimental data reveals that higher-order corrections can predict the measured reflectivity of the samples much better than an often-applied zeroth-order correction.

The change from a mainly vegetarian fare to meat consumption went along with brain growth and increased insulin resistance to improve brain's glucose supply. Meat consumption increased iron bioavailability and, thus, physical and mental fitness. The "predation-release-hypothesis" proposes that group coordination, arms and fire abolished the survival advantage of lean individuals from predation. The "thrifty gene-hypothesis", in contrast, proposes that surviving repeated episodes of starvation increased efficiency of food utilization in the offspring; they learned to utilize every available calorie. As a consequence of either mechanism, improved food security will increase prevalence of obesity along with that of its fatal consequences, such as diabetes, hypertension, heart diseases, and cancer. Thus, improved food security collides with the biologically evolved mechanisms to store excessive calories in preparation for a famine that never came. The crash between homoeostatic mechanisms and human intervention caused the presently observed pandemia of obesity and explains why it is so difficult to avoid, in spite of its well known and often fatal consequences., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

Adipose tissue plasticity mediated by inflammation is an important evolutionary achievement to survive seasonal climate changes. It permits to store excessive calories and to release them if required, using inflammatory cells to remove the debris. This process is regulated by a complex interaction of cytokines (TNF-α, IL-6), adipokines (adiponectin, apelin, liptin), adhesion molecules (ICAM-1, VCAM-1, E-selectin) and transcription factors (NF-κB, HIF-1α). Iron mediates electron transfer as an essential component of e.g. myeloperoxidase, hemoglobin, cytochrome C and ribonucleotide reductase. Conversely, unbound iron can catalyze oxidation of lipids, proteins, and DNA. To balance the essential with the potentially toxic function requires an efficient iron homoeostasis. This is mediated by hepcidin's interaction with the iron-exporter ferroportin, to adapt intestinal iron absorption and body iron-sequestration to changes in demand. In addition, the interaction of iron-responsive elements (IRE) and iron-responsive proteins (IRP), the IRE/IRP-mechanism, regulates cellular iron homoeostasis. Obesity-induced inflammation interacts with both these mechanisms and disturbs iron availability by impairing its absorption, and by sequestering it in the reticuloendothelial system. Both mechanisms lead to anemia and reduce physical fitness which, in a vicious cycle, can support the development of pathological obesity. Thus, interaction between these two sets of beneficial regulatory mechanisms can become detrimental in situations of ample calorie supply., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

The objective was to explore how ferritin-H deletion influences (59)Fe-distribution and excretion-kinetics in mice. Kinetics of (59)Fe-release from organs, whole-body excretion, and distribution-kinetics of intravenously injected (59)Fe trace amounts were compared in iron-deficient and iron-replete mice with (Fth(Δ/Δ)) and without (Fth(lox/lox)) conditional Mx-Cre-induced ferritin-H deletion. (59)Fe was released from spleen and liver beginning on day 2 and day 5 after ferritin-H deletion, respectively, but was not excreted from the body. Plasma-(59)Fe was cleared significantly faster in iron-deficient Fth(Δ/Δ)-mice than in iron-adequate Fth(lox/lox)-controls. (59)Fe-distribution showed a transient peak (e.g., in heart, kidney, muscle) in Fth(lox/lox) control mice, but not in ferritin-H-deleted Fth(Δ/Δ) mice 24 hours after (59)Fe injection. (59)Fe uptake into the liver and spleen was significantly lower in iron-deficient Fth(Δ/Δ) than in Fth(lox/lox) mice 24 hours and 7 days after injection, respectively, and rapidly appeared in circulating erythrocytes instead. The rate of (59)Fe release after ferritin-H deletion supports earlier data on ferritin turnover in mammals; released (59)Fe is not excreted from the body. Instead, (59)Fe is channeled into erythropoiesis and circulating erythrocytes significantly more extensively and faster. Along with a lack of transient interim (59)Fe storage (e.g., in the heart and kidney), this finding is evidence for ferritin-related iron storage-capacity affecting rate and extent of iron utilization., (Copyright © 2014 ISEH - Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.)