Quasi-Baer Rings with Essential Prime Radicals

A ring R is called “quasi-Baer” if the right annihilator of every right ideal is generated, as a right ideal, by an idempotent. It can be seen that a quasi-Baer ring cannot be a right essential extension of a nilpotent right ideal. Birkenmeier asked: Does there exist a quasi-Baer ring which is a right essential extension of its prime radical? We answer this question in the affirmative. Moreover, we provide an example of a quasi-Baer ring in which the right essentiality of the prime radical does not imply the left essentiality of the prime radical.     

Dynamical analysis of an anemoscope in the phase plane

We study the dynamical aspects of an anemoscope indicating a wind direction by constructing a model in the discrete view of fluid. Due to the non-linearity of the rotational equation, the geometrical method is applied for the qualitative analysis. For a given wind direction, there are two fixed points of the parallel and anti-parallel configurations. Near the anti-parallel configuration of the stable fixed point, the anemoscope performs a damped harmonic oscillation. It can be noteworthy that there is always the damping term for both the configurations even in the absence of the non-aerodynamic frictional force from, for example, the axis of rotation. The argument using the index of a closed curve in the phase portrait seems to support the non-existence of periodic solution.     

Synthesis of phenanthro[1,10,9,8‐cdefg]carbazole‐based conjugated polymers for organic solar cell applications

Low bandgap polymers with dithienylquinoxaline moieties based on 6H‐phenanthro[1,10,9,8‐cdefg]carbazole were synthesized via the Suzuki coupling reaction. Alkoxy groups were substituted at two different positions on the phenyl groups of the quinoxaline units of these polymers: in the para‐position (PPQP) and in the meta‐position (PPQM). The two polymers showed similar physical properties: broad absorption in the range of 400–700 nm, optical bandgaps of ～1.8 eV, and the appropriate frontier orbital energy levels for efficient charge transfer/separation at polymer/PC₇₁BM interfaces. However, the PPQM solar cell achieved a higher PCE due to its higher J_sc. Our investigation of the morphologies of the polymer:PC₇₁BM blend films and theoretical calculations of the molecular conformations of the polymer chains showed that the polymer with the meta‐positioned alkoxy group has better miscibility with PC₇₁BM than the polymer with the para‐positioned alkoxy group because the dihedral angle of its phenyl group with respect to the quinoxaline unit is higher. This higher miscibility resulted in a polymer:PC₇₁BM blend film with a better morphology and thus in a higher PCE. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 796–803     

Photogenerated polyelectrolyte bilayers from an aqueous-processible photoresist for multicomponent protein patterning

A novel photoresist (PR) that can be processed under mild aqueous conditions was synthesized and used to create photogenerated polyelectrolyte bilayers. Thin films of the PR cast on polycation-coated substrates were exposed to UV irradiation to generate carboxylate groups in the photoresist. The bulk of the UV-exposed PR film was dissolved by rinsing with pH 7.4 phosphate-buffered saline, but a polyelectrolyte bilayer formed in situ at the PR/polycation interface on exposure remained bound to the substrate. The UV-exposed photoresist also exhibited pH-dependent solubility; it was soluble in water above pH 6.6, but insoluble at lower pHs. Using these unique properties, two-component protein patterning was achieved using biotinylated PR films under conditions that avoid exposing the proteins to conditions outside the narrow range of physiological pH, ionic strength, and temperature where their stability is greatest.     

239+240Pu concentrations of sediments and seawater in the coastal sea of Korea

Summary The ^239+240Pu content of the marine sediments and seawater of the costal sea of Korea was measured. In marine sediments the ^239+240Pu concentrations were in the range of 0.11-1.91 Bq/kg dry weight and in the coastal sea of Korea the ratio of ^239+240Pu/¹³⁷Cs was 0.27. The correlations between ^239+240Pu and ¹³⁷Cs concentrations and the content of organic matter (C, O, H, N, S) as well as the grain size of marine sediment were investigated by regression analysis. The distribution coefficient of ^239+240Pu was 1.22^. 10⁵. The ^239+240Pu concentration in seawater increased with seawater depth. However, the ¹³⁷Cs concentration in seawater did not change considerably with depth.     

Variable energy gap of SiCN nanopowders

SiCN and SiC nanopowders were prepared by infrared laser pyrolysis of gaseous precursors starting from a SiH₄C₂H₂NH₃ gas mixture. The SiCN powders were composed of an amorphous phase ascribed to the ternary compound with a β-SiC crystalline phase, while the SiC powders consisted of β phase only. The chemical bonding and the local atomic order in the SiCN powders are much more complicated than those of pure SiCSi₃N₄ mixtures and are strongly dependent on the variation in the initial gas composition. The average grain size was estimated from X-raydiffraction (XRD) patterns and atomic force microscopy (AFM). The UV-VIS transmittance data were used for the bandgap determination in these new materials. Absorption studies suggested that the direct energy gap is more favourable in SiCN and SiC nanoparticles and is blueshifted with regard to the crystalline bulk (SiC). The change of type of band-to-band transition in SiC nanopowders, due to the size effects, and increasing of the energy gap value in SiCN powders with different local atomic arrangement, makes them attractive for blue-UV optoelectronic applications. PACS 61.46.+w; 78.70.Ck; 68.3.Ps; 78.40.-q     

Visualizations of the transitional flow patterns at the mid-span between shrouded co-rotating disks

Transitional air flow patterns at the mid-plane of gap between co-rotating disks in a stationary cylindrical enclosure are visualized under the acceleration condition of disks. The flow visualization is performed using olive oil particles with a laser sheet and CCD camera. On disk spinning-up, the transition flow patterns are clearly observed. The affect of magnitude of acceleration on the onset of transition and the relations of the number of vortex cells in fully turbulent regime of the flow in an outer region of the flow field to the rotating speed are also investigated. The centrifugal effect of particle is evaluated from the comparison with visualization results using hollow glass spheres.     

Nematic domains and resistivity in an itinerant metamagnet coupled to a lattice

The nature of the emergent phase near a putative quantum critical point in the bilayer ruthenate Sr3Ru2O7 has been a recent subject of intensive research. It has been suggested that this phase may possess electronic nematic order (ENO). In this work, we investigate the possibility of nematic domain formation in the emergent phase, using a phenomenological model of electrons with ENO and its coupling to lattice degrees of freedom. The resistivity due to the scattering off the domain walls is shown to closely follow the ENO parameter. Our results provide qualitative explanations for the dependence of the resistivity on external magnetic fields in Sr3Ru2O7.     

Simultaneous synthesis and consolidation of nanostuctured MgAl2O4 compound by high-frequency induction heated sintering

The rapid sintering of a nanostuctured MgAl₂O₄ compound in a short time was investigated with high-frequency induction heating sintering process. The advantage of this process is that it allows very quick densification to near theoretical density and prohibition of grain growth in nanostuctured materials. A highly dense nanostructured MgAl₂O₄ compound was produced with simultaneous application of 80 MPa pressure and induced current with output of total power capacity (15 kW) within 2 min. The sintering behavior, grain size, and mechanical properties of the MgAl₂O₄ compound were investigated.