Unidirectional broadband light emission from supported plasmonic nanowires

Metal nanowires are thought to become key elements in future nanophotonics applications. Here we show that single crystal silver nanowires supported on a dielectric interface behave similar to broadband unidirectional antennas for visible light. The degree of directionality can be controlled through the nanowire radius and its dielectric environment and the effect can be interpreted in terms of so-called leakage radiation from surface plasmons propagating in a single direction along a wire. We measure a forward-to-backward emission ratio exceeding 15 dB and an angular spread of 4° for wires with radii of the order 150 nm on glass in air. These findings could pave the way for development of metal nanowires as subwavelength directors of light in solar, sensor, and spectroscopy applications.     

Structure of Urethane Copolymers of 3,3‐Bis(azidomethyl)oxetane and 3‐Azidomethyl‐3‐methyloxetane

Polyurethane copolymers of 3,3‐bis (azidomethyl) oxetane (BAMO) and 3‐azidomethyl‐3‐methyloxetane (AMMO) with molecular structures of types B(AB)n, A(AB)n, (BB)n and ABn with different ratios of oligomeric units were investigated, where A is the non‐crystallizable “soft” block of oligoAMMO and B is the “hard” block of oligoBAMO and the included urethane diol fragments. The amorphous‐crystalline structures of copolymers BAMO and AMMO were elucidated by wide angle X‐ray diffraction measurements. The influences of the molecular structure and the ratio of oligomeric units on the structural parameters were identified. The degree of crystallinity is in a range from 8 to 22 % and sizes of the crystallites were determined. The defectivenesses of first and second kind in the structure were evaluated, which show high values of the first kind defectiveness (approx. 20 %), which describes the displacement of theoretical lattice sites and the existence of unequal sizes of the lattice sites, and minor values for the second kind defectiveness (approx. 3 %), which describes the lattice site disorder in large distances. Small‐angle X‐ray diffraction measurements were used to investigate the domain structures of copolymers BAMO and AMMO. The distribution and sizes of the crystallites in the structures of the copolymers were calculated.     

Ni and Cu incorporated mesoporous nanocomposite catalytic materials

Nickel and copper incorporated MCM-41-like mesoporous nanocomposite materials prepared by the direct hydrothermal synthesis and the impregnation procedures showed highly attractive pore structure and surface area results for catalytic applications. The XRD patterns showed that characteristic MCM-41 structure was preserved for the materials synthesized following an impregnation procedure before the calcination step. The surface area of the Cu impregnated material with a quite high Cu/Si atomic ratio (0.19) was 631 m2/g. Very narrow pore size distributions with an average pore diameter of about 2.7 nm were obtained as a result of plugging of some of the smaller pores by Cu nanoballs. For lower metal to Si ratios (for instance for Ni/Si = 0.06) much higher surface area values (1130 m2/g) were obtained. In the case of nanocomposite materials synthesized by the direct hydrothermal route, MCM-41 structure was not destroyed for samples containing metal to Si atomic ratios as high as 0.12. In the case of materials containing Cu/Si and Ni/Si ratios over 0.2 wider pore size distributions and some decrease of surface area were observed.     

Stability of phase-contrast tomography

Phase-contrast tomography (PCT) allows three-dimensional imaging of objects that display insufficient contrast for conventional absorption-based tomography. We prove that PCT is stable with respect to high-frequency noise in experimental phase-contrast data, unlike conventional tomography, which is known to be mildly unstable. We use known properties of the three-dimensional x-ray transform and transport-of-intensity equation to construct a matrix representation of the forward PCT operator. We then invert this formula to show that, under natural boundary conditions, the PCT reconstruction operator exists and leads to a unique solution. We show that the singular values s(n) of the reconstruction operator have asymptotic behavior s(n)=O(n(-3/2)), guaranteeing the mathematical stability of the reconstruction process.     

Activity Comparison of Different Solid Acid Catalysts in Etherification of Glycerol with tert-Butyl Alcohol in Flow and Batch Reactors

In the presented work, etherification of glycerol with TBA was investigated in a continuous flow and also in a batch reactor using nine different commercial solid acid catalysts, namely Amberlyst-15, Amberlyst-36, Amberlyst-35, Amberlyst-16, Relite EXC8D, Lewatit K2629, H-Beta, H-Mordenite and Nafion SAC-13. Results proved the advantages of flow reactor to achieve quite high glycerol conversion values in very short residence times, due to efficient contact of reactants with the solid catalyst, which was caused by higher catalyst to reactant ratio within the reactor. Results of batch reactor experiments obtained in the temperature range of 80–200 °C proved the importance of operating temperature on the catalytic performance of these materials. Amberlyst-15, which has the highest Brønsted acidity, gave the highest glycerol conversion at 90–100 °C. However, this material is unstable at temperatures higher than 110 °C. Performances of Amberlyst-36 and Relite EXC8D were the best in the range of 110–150 °C, which started to become unstable at 150 °C. Although the catalytic performance of Nafion-SAC-13 was not as good as Amberlyst type resins at temperatures up to 150 °C, its thermal stability was higher and could be used up to 200 °C. Although Brønsted acidity was the most important property of these materials in the etherification reaction of glycerol, results also proved the importance of diffusion resistance on the observed conversion values, which limited the penetration of glycerol to the active acid sites, especially in the catalysts with smaller pore diameters and at lower temperatures. Increased significance of swelling at higher temperatures, especially with Amberlyst-36 which had lower cross-linking in its structure and less rigidity, contributed to the penetration of the reactants to the active sites. Water produced during the etherification reaction was also shown to cause deactivation of the catalysts by reversible adsorption on the acid sites.     

PAMAM-calix-dendrimers: Synthesis and Thiacalixarene Conformation Effect on DNA Binding

A convenient method for the synthesis of the first generation PAMAM dendrimers based on the thiacalix[4]arene has been developed for the first time. Three new PAMAM-calix-dendrimers with the macrocyclic core in cone, partial cone, and 1,3-alternate conformations were obtained with high yields. The interaction of the obtained compounds with salmon sperm DNA resulted in the formation of the associates of the size up to 200 nm, as shown by the UV-Vis spectroscopy, DLS, and TEM. It was demonstrated by the CD method that the structure of the DNA did not undergo significant changes upon binding. The PAMAM-calix-dendrimer based on the macrocycle in cone conformation stabilized DNA and prevented its degradation.     

New class of 2,5-di(2-thienyl)pyrrole compounds and novel optical properties of its conducting polymer

New type 2,5-di(2-thienyl)pyrrole derivative namely 4-amino-N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzamide (HKCN) have been synthesized via reaction of 1,4-di(2-thienyl)-1,4-butanedione and p-aminobenzoyl hydrazide. Using hydrazide instead of amine not only increases product yield but also improves properties of the corresponding polymer. Spectroelectrochemical investigations revealed that P(HKCN) is more stable and it has lowest band gap and better long-term stability compared with other SNS derivatives. Chronoamperometry experiment showed that P(HKCN) polymer film has excellent redox stability, moderate switching time and high optical contrast. Electrochemical copolymerization of HKCN with EDOT was performed in DCM/TBP₆ solution for different feed ratios of monomers. We describe a proposal to determination copolymer composition by means of the optical properties of conducting copolymers.     

The Role of Glycogen Synthase Kinase-3 in the Regulation of Ribosome Biogenesis in Rat Soleus Muscle under Disuse Conditions

It is well-established that prolonged exposure to real or simulated microgravity/disuse conditions results in a significant reduction in the rate of muscle protein synthesis (PS) and loss of muscle mass. Muscle protein synthesis is largely dependent upon translational capacity (ribosome content), the regulation of which is poorly explored under conditions of mechanical unloading. Glycogen synthase kinase-3 (GSK-3) (a negative regulator of PS) is known to be activated in rat soleus muscle under unloading conditions. We hypothesized that inhibition of GSK-3 activity under disuse conditions (hindlimb suspension, HS) would reduce disuse-induced downregulation of ribosome biogenesis in rat soleus muscle. Wistar rats were randomly divided into four groups: (1) vivarium control (C), (2) vivarium control + daily injections (4 mg/kg) of AR-A014418 (GSK-3 inhibitor) for 7 days, (3) 7-day HS, (4) 7-day HS + daily injections (4 mg/kg) of AR-A014418. GSK-3beta and glycogen synthase 1 (GS-1) phosphorylation levels were measured by Western-blotting. The key markers of ribosome biogenesis were assessed via agarose gel-electrophoresis and RT-PCR. The rate of muscle PS was assessed by puromycin-based SUnSET method. As expected, 7-day HS resulted in a significant decrease in the inhibitory Ser9 GSK-3beta phosphorylation and an increase in GS-1 (Ser641) phosphorylation compared to the C group. Treatment of rats with GSK-3 inhibitor prevented HS-induced increase in GS1 (Ser641) phosphorylation, which was indicative of GSK-3 inhibition. Administration of GSK-3 inhibitor partly attenuated disuse-induced downregulation of c-Myc expression as well as decreases in the levels of 45S pre-rRNA and 18S + 28S rRNAs. These AR-A014418-induced alterations in the markers of ribosome biogenesis were paralleled with partial prevention of a decrease in the rate of muscle PS. Thus, inhibition of GSK-3 during 7-day HS is able to partially attenuate the reductions in translational capacity and the rate of PS in rat soleus muscle.     

Structure-Functional Characteristics of the Svx Protein—The Virulence Factor of the Phytopathogenic Bacterium Pectobacterium atrosepticum

The Svx proteins are virulence factors of phytopathogenic bacteria of the Pectobacterium genus. The specific functions of these proteins are unknown. Here we show that most of the phytopathogenic species of Pectobacterium, Dickeya, and Xanthomonas genera have genes encoding Svx proteins, as well as some plant-non-associated species of different bacterial genera. As such, the Svx-like proteins of phytopathogenic species form a distinct clade, pointing to the directed evolution of these proteins to provide effective interactions with plants. To get a better insight into the structure and functions of the Svx proteins, we analyzed the Svx of Pectobacterium atrosepticum (Pba)—an extracellular virulence factor secreted into the host plant cell wall (PCW). Using in silico analyses and by obtaining and analyzing the recombinant Pba Svx and its mutant forms, we showed that this protein was a gluzincin metallopeptidase. The 3D structure model of the Pba Svx was built and benchmarked against the experimental overall secondary structure content. Structure-based substrate specificity analysis using molecular docking revealed that the Pba Svx substrate-binding pocket might accept α-glycosylated proteins represented in the PCW by extensins—proteins that strengthen the PCW. Thus, these results elucidate the way in which the Pba Svx may contribute to the Pba virulence.     

Alcohol breeds empty goal commitments.

According to alcohol-myopia theory (C. M. Steele & R. A. Josephs, 1990), alcohol leads individuals to disproportionally focus on the most salient aspects of a situation and to ignore peripheral information. The authors hypothesized that alcohol leads individuals to strongly commit to their goals without considering information about the probability of goal attainment. In Study 1, participants named their most important interpersonal goal, indicated their expectations of successfully attaining it, and then consumed either alcohol or a placebo. In contrast to participants who consumed a placebo, intoxicated participants felt strongly committed to their goals despite low expectations of attaining them. In Study 2, goal-directed actions were measured over time. Once sober again, intoxicated participants with low expectations did not follow up on their strong commitments. Apparently, when prospects are bleak, alcohol produces empty goal commitments, as commitments are not based on individuals’ expectations of attaining their goals and do not foster goal striving over time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)