Synthesis of multiarmed poly(3‐hexyl thiophene) star polymer with microgel core by GRIM and ATRP methods

Regioregular poly(3‐hexyl thiophene) (rr‐P3HT)‐based star polymers were synthesized by a crosslinking reaction of the linear rr‐P3HT macroinitiator and ethylene glycol dimethacrylate (EGDMA) crosslinker through Ru‐based atom transfer radical polymerization (ATRP), where the rr‐P3HT macroinitiator was prepared by Grignard metathesis method (GRIM) followed by end functionalization of the ATRP initiator with chlorophenylacetate (CPA) to the rr‐P3HT. Relatively high molecular weight of the star polymers were obtained (M_p = 8,988,000 g/mol), which consisted of large numbers of the rr‐P3HT arm chains radiating from the EGDMA‐based microgel core. The yield of the star polymers were strongly affected by the added amount of the EGDMA crosslinker. The crystalline structure of the rr‐P3HT by intermolecular π‐π stacking interaction gradually decreased as the star polymer formed, which was confirmed by differential scanning calorimeter (DSC), atomic force microscopy (AFM), and electro‐optical analyses. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Hybrid ring coupler for W-band MMIC applications using MEMS technology

The hybrid ring coupler was designed and fabricated on a GaAs substrate using surface micromachining techniques, which adopted dielectric-supported air-gapped microstrip line (DAML) structure. The fabrication process of DAML is compatible with the standard monolithic microwave integrated circuit (MMIC) techniques, and the hybrid ring coupler can be simply integrated into a plane-structural MMIC. The fabricated hybrid ring coupler shows wideband characteristics of the coupling loss of 3.57 /spl plusmn/ 0.22dB and the transmission loss of 3.80 /spl plusmn/ 0.08dB across the measured frequency range of 85 to 105GHz. The isolation characteristics and output phase differences are -34dB and 180/spl plusmn/1/spl deg/, at 94GHz, respectively.     

Toll-like receptor 9-mediated inhibition of apoptosis occurs through suppression of FoxO3a activity and induction of FLIP expression

Synthetic oligodeoxynucleotides (ODN) with a CpG-motif are recognized by Toll-like receptor 9 (TLR9) and pleiotropic immune responses are elicited. Stimulation of macrophages with TLR9 agonist prevented apoptosis induced by serum deprivation through increased expression of FLICE-like inhibitory protein (FLIP). CpG ODN-mediated anti-apoptosis depended on the TLR9-Akt-FoxO3a signaling pathway. Inhibition of TLR9 by small interfering (si) RNA or an inhibitor suppressed CpG ODN-mediated anti-apoptosis. Analysis of signaling pathways revealed that the anti-apoptotic effect of CpG ODN required phosphorylation of FoxO3a and its translocation from the nucleus to the cytosol. Overexpression of FoxO3a increased apoptosis induced by serum deprivation and CpG ODN blocked these effects through FLIP expression. In contrast, siRNA knock-down of FoxO3a decreased apoptosis by serum deprivation. In addition, Akt activation was involved in CpG ODN-induced phosphorylation of FoxO3a, expression of FLIP, and anti-apoptosis. Taken together, these results demonstrate the involvement of Akt-FoxO3a in TLR9-mediated anti-apoptosis and indicate that FoxO3a is a distinct regulator for FLIP expression.     

Testing a priority-based queue model with Linux command histories

We study human dynamics by analyzing Linux history files. The goodness-of-fit test shows that most of the collected datasets belong to the universality class suggested in the literature by a variable-length queuing process based on priority. In order to check the validity of this model, we design two tests based on mutual information between time intervals and a mathematical relationship known as the arcsine law. Since the previously suggested queuing process fails to pass these tests, the result suggests that the modelling of human dynamics should properly consider the statistical dependency in the temporal dimension.     

Competition Between Radial Expansion and Thickening in the Enlargement of an Intracranial Saccular Aneurysm

Rupture of intracranial saccular aneurysms is the leading cause of spontaneous subarachnoid hemorrhage, which results in significant morbidity and mortality. Although many have suggested that saccular aneurysms enlarge and rupture due to mechanical instabilities, our recent nonlinear analyses suggest that at least certain classes of aneurysms do not exhibit a quasi-static limit point instability or dynamic instabilities in response to periodic loading. Based on an increased understanding of the ubiquitous role of growth and remodeling within the vasculature and recent histopathological data on saccular aneurysms, it is hypothesized that a stress-mediated regulation of collagen turnover causes their enlargement. There is a need, however, for a theoretical framework to explore this and competing hypotheses. In this paper, we present a 2-D constrained mixture model for growth and remodeling of an ellipsoidally shaped saccular aneurysm and numerically simulate enlargement and changes in material symmetry in the aneurysmal wall. Results suggest that ellipsoidal aneurysms tend toward spherical shapes, and a competition between radial expansion and wall thickening plays a critical role in determining the stability of an enlarging lesion.     

Direct glycosylation with anomeric hydroxy sugars by activation with 3-fluorophthalic anhydride and trifluoromethanesulfonic anhydride

An efficient and direct one-pot glycosylation method using anomeric hydroxy sugars as glycosyl donors, employing 3-fluorophthalic anhydride and triflic anhydride as activating agents, has been developed. The present glycosylation utilizing 3-fluorophthalic anhydride resulted in few to no undesired self-condensed esters than the glycosylation using phthalic anhydride. Intermediates in the present glycosylation were identified by an NMR study.     

A Fully-Differential Complementary Hartley VCO in 0.18 m CMOS Technology

In this letter, a new complementary Hartley (C-Hartley) voltage controlled oscillator (VCO) with fully differential outputs is proposed, in which the self-biasing configuration is introduced to solve the biasing difficulty of a Hartley VCO by employing a five-port transformer. The proposed C-Hartley VCO with the center frequency of 5.6 GHz is implemented in a 1P6M 0.18 $mu$m CMOS process. The measurement result shows that the phase noise is ${-}123.6$ dBc/Hz at 1 MHz offset frequency, while dissipating 6.5 mA from 1.6 V supply with the FOM of ${-}188.5$ dBc.      

Electromigration-Induced Plastic Deformation in Cu Interconnects: Effects on Current Density Exponent, <Emphasis Type="Italic">n</Emphasis>, and Implications for EM Reliability Assessment

While Black’s equation for electromigration (EM) in interconnects with n = 1 is rigorously based on the principles of electrotransport, n > 1 is more commonly observed empirically. This deviation is usually attributed to Joule heating. An alternative explanation is suggested by the recent discovery of EM plasticity. To examine this possibility, we have retested samples that had been previously subjected to a predamaging phase of high temperature and current densities to determine whether the loss of median time to failure (MTF) is retained. We find that the predamaged samples exhibit MTFs that are permanently reduced, which is a characteristic of EM plasticity.     

Sub-iteration leads to accuracy and stability enhancements of semi-implicit schemes for the Navier–Stokes equations

We present an iterative semi-implicit scheme for the incompressible Navier–Stokes equations, which is stable at CFL numbers well above the nominal limit. We have implemented this scheme in conjunction with spectral discretizations, which suffer from serious time step limitations at very high resolution. However, the approach we present is general and can be adopted with finite element and finite difference discretizations as well. Specifically, at each time level, the nonlinear convective term and the pressure boundary condition – both of which are treated explicitly in time – are updated using fixed-point iteration and Aitken relaxation. Eigenvalue analysis shows that this scheme is unconditionally stable for Stokes flows while numerical results suggest that the same is true for steady Navier–Stokes flows as well. This finding is also supported by error analysis that leads to the proper value of the relaxation parameter as a function of the flow parameters. In unsteady flows, second- and third-order temporal accuracy is obtained for the velocity field at CFL number 5–14 using analytical solutions. Systematic accuracy, stability, and cost comparisons are presented against the standard semi-implicit method and a recently proposed fully-implicit scheme that does not require Newton’s iterations. In addition to its enhanced accuracy and stability, the proposed method requires the solution of symmetric only linear systems for which very effective preconditioners exist unlike the fully-implicit schemes.     

RKKY ferromagnetism with Ising-like spin states in intercalated Fe(1/4)TaS2

We investigated the magnetic nature of Fe(1/4)TaS2 using x-ray absorption spectroscopy, photoemission spectroscopy, and first principles band calculations. The results show a large unquenched orbital magnetic moment (～1.0 μ(B)/Fe) at intercalated Fe sites, resulting in a gigantic magnetic anisotropy (H(A)?60 T). The magnetic coupling is well understood in terms of the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, suggesting a novel RKKY ferromagnet with Ising-type spin states. We also found that this indirect exchange coupling between the neighboring Fe spins is ferromagnetic and maximized at the Fe-Fe distance of 2×2 superstructure.