Local and landscape responses of biodiversity in calcareous grasslands

Biodiversity and Conservation - Across Europe, calcareous grasslands become increasingly fragmented and their quality deteriorates through abandonment and land use intensification, both affecting...     

How calcium signals in myocytes and pericytes are integrated across in situ microvascular networks and control microvascular tone

The microcirculation is the site of gas and nutrient exchange. Control of central or local signals acting on the myocytes, pericytes and endothelial cells within it, is essential for health. Due to technical problems of accessibility, the mechanisms controlling Ca²⁺ signalling and contractility of myocytes and pericytes in different sections of microvascular networks in situ have not been investigated. We aimed to investigate Ca²⁺ signalling and functional responses, in a microcirculatory network in situ. Using live confocal imaging of ureteric microvascular networks, we have studied the architecture, morphology, Ca²⁺ signalling and contractility of myocytes and pericytes. Ca²⁺ signals vary between distributing arcade and downstream transverse and precapillary arterioles, are modified by agonists, with sympathetic agonists being ineffective beyond transverse arterioles. In myocytes and pericytes, Ca²⁺ signals arise from Ca²⁺ release from the sarcoplasmic reticulum through inositol 1,4,5-trisphosphate-induced Ca²⁺ release and not via ryanodine receptors or Ca²⁺ entry into the cell. The responses in pericytes are less oscillatory, slower and longer-lasting than those in myocytes. Myocytes and pericytes are electrically coupled, transmitting Ca²⁺ signals between arteriolar and venular networks dependent on gap junctions and Ca²⁺ entry via L-type Ca²⁺ channels. Endothelial Ca²⁺ signalling inhibits intracellular Ca²⁺ oscillations in myocytes and pericytes via L-arginine/nitric oxide pathway and intercellular propagating Ca²⁺ signals via EDHF. Increases of Ca²⁺ in pericytes and myocytes constrict all vessels except capillaries. These data reveal the structural and signalling specializations allowing blood flow to be regulated by myocytes and pericytes.     

Targeted delivery of doxorubicin: Drug delivery system based on PAMAM dendrimers

Polyamidoamine (PAMAM) dendrimers of the second generation (G2) are branched polymers containing 16 surface amino groups that allow them to be used as universal carriers on creating systems for drug delivery. G2 labeled with fluorescein isothiocyanate (FITC) efficiently bound with the surface of tumor cells at 4°C and was absorbed by the cells at 37°C. The covalent binding to G2-FITC of a vector protein, a recombinant fragment of the human alpha-fetoprotein receptor-binding domain (rAFP3D), increased the binding and endocytosis efficiency more than threefold. Covalent conjugates of G2 with doxorubicin (Dox) obtained by acid-labile linking of cis-aconitic anhydride (CAA) without the vector protein (G2-Dox) and with the vector protein rAFP3D (rAFP3D-G2-Dox) were accumulated by the tumor cells with high efficiency. However, a selective effect was observed only in rAFP3D-G2-Dox, which also demonstrated high cytotoxic activity against the human ovarian adenocarcinoma SKOV3 cells and low cytotoxicity against human peripheral blood lymphocytes. Based on these results, rAFP3D-G2 conjugate is promising for selective delivery of antitumor drugs.     

Validated numerical fluid simulation of a thin‐layer cascade photobioreactor in OpenFOAM

Recently, microalgae have been considered as a promising alternative for the production of biofuels from CO₂. For the efficient cultivation of these microalgae, several types of photobioreactors have been designed and Pilot scale photobioreactors have been used to assess the performance of these reactors. Therein the primarily investigated reactor type is the Raceway Pond. However, the less researched Thin‐Layer Cascade Photobioreactor (TLC) shows a high potential for efficient production processes. Unfortunately, for low‐value products like biofuels costs must be kept to a minimum for an economic operation. To facilitate this, 3D Computational Fluid Dynamic simulations can be employed to estimate performance of reactor variants e.g. with respect to power input and mixing. Since up to now little effort has been put into the modelling of TLC reactors, this report aims to present a simulation approach for these reactors types that allows simple adaptation to different geometric or operational boundary conditions. All models have been generated for a two‐phase mixture in OpenFOAM. To demonstrate its applicability, validation measurements with a physical unit have been performed and were compared to the simulation results. With errors in the order of 10 % a successful simulation of the reactor geometry could be proven.     

Investigating the Role of 4‐Tert Butylpyridine in Perovskite Solar Cells

The majority of hole‐transporting layers used in n‐i‐p perovskite solar cells contain 4‐tert butylpyridine (tBP). High power‐conversion efficiencies and, in particular, good steady‐state performance appears to be contingent on the inclusion of this additive. On the quest to improve the steady state efficiencies of the carbon nanotube‐based hole‐transporter system, this study has found that the presence of tBP results in an extraordinary improvement in the performance of these devices. By deconstructing a prototypical device and investigating the effect of tBP on each individual layer, the results of this study indicate that this performance enhancement must be due to a direct chemical interaction between tBP and the perovskite material. This study proposes that tBP serves to p‐dope the perovskite layer and investigates this theory with poling and work function measurements.     

Elucidating the Role of a Tetrafluoroborate‐Based Ionic Liquid at the n‐Type Oxide/Perovskite Interface

Halide perovskites are currently one of the most heavily researched emerging photovoltaic materials. Despite achieving remarkable power conversion efficiencies, perovskite solar cells have not yet achieved their full potential, with the interfaces between the perovskite and the charge‐selective layers being where most recombination losses occur. In this study, a fluorinated ionic liquid (IL) is employed to modify the perovskite/SnO₂ interface. Using Kelvin probe and photoelectron spectroscopy measurements, it is shown that depositing the perovskite onto an IL‐treated substrate results in the crystallization of a perovskite film which has a more n‐type character, evidenced by a decrease of the work function and a shift of the Fermi level toward the conduction band. Photoluminescence spectroscopy and time‐resolved microwave conductivity are used to investigate the optoelectronic properties of the perovskite grown on neat and IL‐modified surfaces and it is found that the modified substrate yields a perovskite film which exhibits an order of magnitude lower trap density than the control. When incorporated into solar cells, this interface modification results in a reduction in the current–voltage hysteresis and an improvement in device performance, with the best performing devices achieving steady‐state PCEs exceeding 20%.     

Doubletten von Vogel-Eiern

Ohne Zusammenfassung     

Current Concepts of the Pathogenesis and Pathology of Inflammatory Lesions of the Intestine

The histopathologic lesions of regional enteritis and ulcerative colitis, particularly in their early stages, are distinct and distinguishable, irrespective of the sites that are involved. Regional enteritis is characterized by lymphangiectasis, lymphedema, lymphoid hyperplasia, and granulomatous inflammation of the submucosal and subserosal layers of intestine, whereas chronic ulcerative colitis is an exudative, ulcerative disorder of the mucosal layer that commences with “crypt abscesses” and only in its later stages progresses to deeper coats of the wall.Electron microscopy of a rectal biopsy from a juvenile patient with chronic ulcerative colitis for five years disclosed a labyrinthine system of clefts and compartments between columnar, mucosal epithelial cells. Regenerated colonic epithelial cells were of primitive, germinal type and featured a “vesicular” rather than a “goblet” pattern of mucus secretion. Clusters of small “clavate fimbriae” projected from the tips of microvilli. Each of these newly recognized substructures measured 30 to 60 mμ. in diameter, and was enclosed by a tri-laminar “unit membrane”, derived from the surface plasma membrane of the cell.     

Stringent response leads to continued cell division and a temporal restart of DNA replication after initial shutdown in Vibrio cholerae

Vibrio cholerae is an aquatic bacterium with the potential to infect humans and cause the cholera disease. While most bacteria have single chromosomes, the V. cholerae genome is encoded on two replicons of different size. This study focuses on the DNA replication and cell division of this bi‐chromosomal bacterium during the stringent response induced by starvation stress. V. cholerae cells were found to initially shut DNA replication initiation down upon stringent response induction by the serine analog serine hydroxamate. Surprisingly, cells temporarily restart their DNA replication before finally reaching a state with fully replicated single chromosome sets. This division‐replication pattern is very different to that of the related single chromosome model bacterium Escherichia coli. Within the replication restart phase, both chromosomes of V. cholerae maintained their known order of replication timing to achieve termination synchrony. Using flow cytometry combined with mathematical modeling, we established that a phase of cellular regrowth be the reason for the observed restart of DNA replication after the initial shutdown. Our study shows that although the stringent response induction itself is widely conserved, bacteria developed different ways of how to react to the sensed nutrient limitation, potentially reflecting their individual lifestyle requirements.