A polymer electrolyte containing ionic liquid for possible applications in photoelectrochemical solar cells

Various iodide ion conducting polymer electrolytes have been studied as candidate materials for fabricating photoelectrochemical (PEC) solar cells and energy storage devices. In this study, enhanced ionic conductivity values were obtained for the ionic liquid tetrahexylammonium iodide containing polyethylene oxide (PEO)-based plasticized electrolytes. The analysis of thermal properties revealed the existence of two phases in the electrolyte, and the conductivity measurements showed a marked conductivity enhancement during the melting of the plasticizer-rich phase of the electrolyte. Annealed electrolyte samples showed better conductivity than nonannealed samples, revealing the existence of hysteresis. The optimum conductivity was shown for the electrolytes with PEO:salt = 100:15 mass ratio, and this sample exhibited the minimum glass transition temperature of 72.2 °C. For this optimum PEO to salt ratio, the conductivity of nonannealed electrolyte was 4.4 × 10⁻⁴ S cm⁻¹ and that of the annealed sample was 4.6 × 10⁻⁴ S cm⁻¹ at 30 °C. An all solid PEC solar cell was fabricated using this annealed electrolyte. The short circuit current density (I _SC), the open circuit voltage (V _OC), and the power conversion efficiency of the cell are 0.63 mA cm⁻², 0.76 V, and 0.47% under the irradiation of 600 W m⁻² light.     

Neural expression and post-transcriptional dosage compensation of the steroid metabolic enzyme 17β-HSD type 4

Background  

Steroids affect many tissues, including the brain. In the zebra finch, the estrogenic steroid estradiol (E₂) is especially effective at promoting growth of the neural circuit specialized for song. In this species, only the males sing and they have a much larger and more interconnected song circuit than females. Thus, it was surprising that the gene for 17β-hydroxysteroid dehydrogenase type 4 (HSD17B4), an enzyme that converts E₂ to a less potent estrogen, had been mapped to the Z sex chromosome. As a consequence, it was likely that HSD17B4 was differentially expressed in males (ZZ) and females (ZW) because dosage compensation of Z chromosome genes is incomplete in birds. If a higher abundance of HSD17B4 mRNA in males than females was translated into functional enzyme in the brain, then contrary to expectation, males could produce less E₂ in their brains than females.     

Binding Modes of Thioflavin T on the Surface of Amyloid Fibrils Studied by NMR

The mechanism for the interaction of thioflavin T (ThT) with amyloid fibrils at the molecular level is not known. Here, we used ¹H NMR spectroscopy to determine the binding mode of ThT on the surface of fibrils from lysozyme and insulin. Relayed rotating‐frame Overhauser enhancements in ThT were observed, indicating that the orientation of ThT is orthogonal to the fibril surface. Importantly, the assembly state of ThT on both surfaces is different. On the surface of insulin fibrils, ThT is oligomeric, as indicated by rapid ¹H spin‐lattice relaxation rate in the rotating frame (R_1ρ), presumably due to intermolecular dipole–dipole interactions between ThT molecules. In contrast, ThT on the surface of lysozyme fibrils is a monomer, as indicated by slower ¹H R_1ρ. These results shed new light into the mechanism for the enhancement of ThT fluorescence and may lead to more efficient detectors of amyloid assemblies, which have escaped detection by ThT in monomer form.     

An experimental test of the scaling prediction for the spatial distribution of water during the drying of colloidal films

A Peclet number, Pe, for the drying of colloidal films can be used as a predictor of the uniformity of water concentration in the direction normal to the film. Uniform drying is predicted to occur when Pe < 1, whereas with , a layer of packed particles is expected to develop above a more dilute layer. Routh and Zimmerman have more recently proposed that the particle concentration gradient between the packed and dilute layers, , will scale as . Here, this scaling relation is tested experimentally with magnetic resonance profiling data obtained from waterborne colloidal films dried under conditions to yield a range of Pe. It is found that increases with Pe but scales as . This disagreement with the prediction can be attributed to an underestimate of Pe when there are greater non-uniformities of drying, because of an unquantified slowing down of the evaporation rate.     

Effect of nanoporous alumina filler on conductivity enhancement in PEO9(MgClO4)2 polymer electrolyte: a 1H NMR study

Ionic conductivity, differential scanning calorimetry (DSC), and ¹H nuclear magnetic resonance (NMR) measurements have been performed on (PEO)₉Mg(ClO₄)₂ and (PEO)₉Mg(ClO₄)₂ + Al₂O₃ (neutral, nanoporous) polymer electrolyte systems. It is observed that the conductivity enhances due to the presence of filler up to 15 wt.% and then decreases. The NMR results are consistent with the idea that the conductivity enhancement is mainly due to the increase in chain mobility and ionic mobility of the solid polymer electrolyte caused by increased amorphocity of the electrolyte due to the presence of filler. DSC results also demonstrate that the fraction of the amorphous phase has increased due to the addition of the filler.     

Aspects of an inventory control study

A case study for the design of a spare parts inventory control system is described. The main emphasis is given to the problems of applying and tailoring forecasting and inventory control theory to suit the needs of a particular problem. In the main, well established methods were used and these are not described in detail. New developments arising in the course of the study have been described elsewhere.     

Model transition states for methane diazonium ion methylation of guanine runs in oligomeric DNA

The DNA reaction pattern of the methane diazonium ion, which is the reactive intermediate formed from several carcinogenic methylating agents, was examined at N7 and O(6) sites in guanine runs occurring in oligonucleotides and model oligonucleotides. Density functional B3LYP/6-31G*, and SCF 3-21G and STO-3G energies of model transition states were calculated in the gas phase and in the CPCM reaction field. For nucleotides containing two, three, and four stacked guanines with counterions in the gas phase, O(6) reactivity is greater than N7 reactivity. In the reaction field, N7 reactivity is 9.0 to 9.8 times greater than O(6) reactivity. For a double-stranded oligonucleotide containing two stacked guanines with counterions in the reaction field, the N7 and O(6) reactivities of the 3'-guanine are 3.9 times greater than the corresponding sites in the 5'-guanine. For double-stranded oligonucleotides with three or four stacked guanines and counterions, the reactivities of the interior guanines are higher than corresponding reactivities of guanines at the ends. These reaction patterns agree with most of the available experimental data. Activation energy decomposition analysis for gas-phase reactions in a double-stranded dinucleotide containing two stacked guanines with counterions indicates that selectivity at O(6) is almost entirely due to electrostatic forces. Selectivity at N7 also has a large electrostatic interaction. However, the orbital interaction also contributes significantly to the gas-phase selectivity, accounting for 32% of the total interaction energy difference between the 3'- and 5'-guanine reactions. In aqueous solution, the relative orbital contribution to N7 selectivity is likely to be larger.     

Free‐electron laser multiplex driven by a superconducting linear accelerator

Free‐electron lasers (FELs) generate femtosecond XUV and X‐ray pulses at peak powers in the gigawatt range. The FEL user facility FLASH at DESY (Hamburg, Germany) is driven by a superconducting linear accelerator with up to 8000 pulses per second. Since 2014, two parallel undulator beamlines, FLASH1 and FLASH2, have been in operation. In addition to the main undulator, the FLASH1 beamline is equipped with an undulator section, sFLASH, dedicated to research and development of fully coherent extreme ultraviolet photon pulses using external seed lasers. In this contribution, the first simultaneous lasing of the three FELs at 13.4 nm, 20 nm and 38.8 nm is presented.     

Diverse Coordination Geometries Derived from Trisaminocyclohexane Ligands with Appended Outer-Sphere Hydrogen Bond Donors

With the aim of constructing hydrogen-bonding networks in synthetic complexes, two new ligands derived from cis,cis-1,3,5-triaminocyclohexane (TACH) have been prepared that feature pendant pyrrole or indole rings as outer-sphere H-bond donors. The TACH framework offers a facial arrangement of three N-donors, thereby mimicking common coordination motifs in the active sites of nonheme Fe and Cu enzymes. X-ray structural characterization of a series of Cu^I-X complexes (X=F, Cl, Br, NCS) revealed that these neutral ligands (H₃L^R, R=pyrrole or indole) coordinate in the intended facial N₃ manner, yielding four-coordinate complexes with idealized C₃ symmetry. The N−H units of the outer-sphere heterocycles form a hydrogen-bonding cavity around the axial (pseudo)halide ligand, as verified by crystallographic, spectroscopic, and computational analyses. Treatment of H₃L^pyrrole and H₃L^indole with divalent transition metal chlorides (M^IICl₂, M=Fe, Cu, Zn) causes one heterocycle to deprotonate and coordinate to the M(II) center, giving rise to tetradentate ligands with two remaining outer-sphere H-bond donors. Further ligand deprotonation is observed upon reaction with Ni(II) and Cu(II) salts with weakly coordinating counteranions. The reported complexes highlight the versatility of TACH-based ligands with pendant H-bond donors, as the resulting scaffolds can support multiple protonation states, coordination geometries, and H-bonding interactions.