Structural variations among the aporphine-benzylisoquinoline dimers

$\text{Thalictrum}$$\text{minus}$ L. var. $\text{microphyllum}$ Boiss. (Ranunculaceae) has yielded (+)-istanbulamine ($\text{5}$) which is the first aporphine-benzylisoquinoline formed from one (+)-reticuline-type unit linked to a (+)-N-methylcoclaurine moiety. Other new dimers also present are (+)-bursanine ($\text{6}$) and (+)-iznikine ($\text{7}$).     

Photoactivity passivation of TiO<Subscript>2</Subscript> nanoparticles using molecular layer deposited (MLD) polymer films

Pigment-grade anatase TiO₂ particles (160 nm) were passivated using ultra-thin insulating films deposited by molecular layer deposition (MLD). Trimethylaluminum (TMA) and ethylene glycol (E.G) were used as aluminum alkoxide (alucone) precursors in the temperature range of 100–160 °C. The growth rate varied from 0.5 nm/cycle at 100 °C to 0.35 nm/cycle at 160 °C. Methylene blue oxidation tests indicated that the photoactivity of pigment-grade TiO₂ particles was quenched after 20 cycles of alucone MLD film, which was comparable to 70 cycles of Al₂O₃ film deposited by atomic layer deposition (ALD). Alucone films would decompose in the presence of water at room temperature and would form a more stable composite containing aluminum, which decreased the passivation effect on the photoactivity of TiO₂ particles.     

Hybrid measurement of auditory steady-state responses and distortion product otoacoustic emissions using an amplitude-modulated primary tone

A maximum auditory steady-state response (ASSR) amplitude is yielded when the ASSR is elicited by an amplitude-modulated tone (f(c)) with a fixed modulation frequency (f(m) = 40 Hz), whereas the maximum distortion product otoacoustic emission (DPOAE) level is yielded when the DPOAE is elicited using a fixed frequency ratio of the primary tones (f2/f1 = 1.2). When eliciting the DPOAE and ASSR by the same tone pair, optimal stimulation is present for either DPOAE or ASSR and thus adequate simultaneous DPOAE/ASSR measurement is not possible across test frequency f2 or f(c), respectively. The purpose of the present study was to determine whether the ASSR and DPOAE can be measured simultaneously without notable restrictions using a DPOAE stimulus setting in which one primary tone is amplitude modulated. A DPOAE of frequency 2f1-f2 and ASSR of modulation frequency 41 Hz were measured in ten normal hearing subjects at a test frequency between 0.5 and 8 kHz (f2 = f(c)). The decrease in the DPOAE level and the loss in ASSR amplitude during hybrid mode stimulation amounted, on average, to only 2.60 dB [standard deviation (SD) = 1.38 dB] and 1.83 dB (SD = 2.38 dB), respectively. These findings suggest simultaneous DPOAE and ASSR measurements to be feasible across all test frequencies when using a DPOAE stimulus setting where the primary tone f2 is amplitude modulated.     

Anomalous bias dependence of spin torque in magnetic tunnel junctions

We predict an anomalous bias dependence of the spin transfer torque parallel to the interface, Tparallel, in magnetic tunnel junctions, which can be selectively tuned by the exchange splitting. It may exhibit a sign reversal without a corresponding sign reversal of the bias or even a quadratic bias dependence. We demonstrate that the underlying mechanism is the interplay of spin currents for the ferromagnetic (antiferromagnetic) configurations, which vary linearly (quadratically) with bias, respectively, due to the symmetric (asymmetric) nature of the barrier. The spin transfer torque perpendicular to interface exhibits a quadratic bias dependence.     

Complexes of 1,2-bis(aryl-imino)acenaphthene (Ar-BIAN) ligands with some heavy p-block elements

The new Ar-BIAN complexes [(mes-BIAN)InCl(3)(THF)] (1), [(mes-BIAN)(2)Tl][PF(6)] (2), [(dipp-BIAN)SnCl(4)] (3), [(dipp-BIAN)SbCl(3)] (4), [(dipp-BIAN)BiCl(3)] (5) and [(mes-BIAN)BiCl(3)] (6) have been prepared by treatment of the neutral mes- and dipp-substituted BIAN ligands with the p-block reagents InCl(3), TlPF(6), SnCl(4), SbCl(3), and BiCl(3). The molecular structures of complexes 1-6 have been determined by single-crystal X-ray diffraction methods. However, only the atom connectivity was established for 5.     

Image subtraction approach to screening one-bead-one-compound combinatorial libraries with complex protein mixtures

To screen one-bead-one-compound (OBOC) combinatorial bead libraries,(1) one generally uses tagged purified protein as the screening probe. Compound beads that interact with the purified protein are then identified, for example, via an enzyme-linked colorimetric assay, and isolated for structure determination. In this report, we demonstrate a rapid and efficient method to screen OBOC combinatorial libraries utilizing two protein mixtures as screening probes, and by comparing optical images of the beads stained by one protein mixture but not the other, ligand beads unique to one of the two protein mixtures can be identified. The significance of this method is that it allows for rapid selection of ligands directed against proteins unique to one mixture while screening out positive beads resulting from proteins common to both mixtures as well as beads that are positive as a result of interactions with chemical and protein components found in the assay itself. The method is fast, efficient, and uses off-the-shelf equipment.     

Chemically stable films for combinatorial fluorosensor arrays

Sensor arrays are useful for many purposes. Our interests include quasi-distributed intrinsic fiber optic arrays, those distributed along the length of an optical fiber. We have demonstrated an optical time-of-flight approach to distinguishing the fluorescence output of such arrays, as well as a synthesis of combinatorial libraries that takes advantage of a support of linear morphology to make numerous compounds in a simple manner without information loss in the synthesis. To unite these research areas, we needed an optical fiber cladding material that meets demanding synthetic and optical requirements. We have chosen the Meldal SPOCC polymer support as the best candidate for such a material and report here our initial results with this material.     

Investigation of free base, Mg, Sn, and Zn substituted porphyrin LB films as gas sensors for organic analytes

The visible absorption spectra of various substituted porphyrin compounds both in chloroform solution and as Langmuir-Blodgett (LB) solid-state films have been investigated. The porphyrin compounds examined were the Zn, Sn, Mg, and free base derivatives of 5,10,15,20-tetrakis[3,4-bis(2-ethylhexyloxy)phenyl]-21H,23H-porphine (EHO). Changes in the absorption spectra of these materials induced by their exposure to various organic compounds are reported with a view toward determining whether this is a useful approach toward an optical gas sensor.     

Large-area highly-oriented SiC nanowire arrays: synthesis, Raman, and photoluminescence properties

Large-area highly oriented SiC nanowire arrays have been fabricated by chemical vapor reaction using an ordered nanoporous anodic aluminum oxide (AAO) template and a graphite reaction cell. Their microstructures were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy. The results show that the nanowires are single-crystalline beta-SiC's with diameters of about 30-60 nm and lengths of about 8 microm, which are parallel to each other, uniformly distributed, highly oriented, and in agreement with the nanopore diameter of the applied AAO template. The nanowire axes lie along the [111] direction and possess a high density of planar defects. Some unique optical properties are found in the Raman spectroscopy and photoluminescence emission from oriented SiC nanowire arrays, which are different from previous observations of SiC materials. The growth mechanism of oriented SiC nanowire arrays is also analyzed and discussed.     

On closures of cycle spaces of flag domains

Open orbits D of noncompact real forms G ₀ acting on flag manifolds Z = G/Q of their semisimple complexifications G are considered. Given D and a maximal compact subgroup K ₀ of G ₀, there is a unique complex K ₀–orbit in D which is regarded as a point in the space of q-dimensional cycles in D. The group theoretical cycle space is defined to be the connected component containing C ₀ of the intersection of the G–orbit G(C ₀) with . The main result of the present article is that is closed in . This follows from an analysis of the closure of the universal domain in any G-equivariant compactification of the affine symmetric space G/K, where K is the complexification of K ₀ in G.