Enhanced stability of 1D molecular lines on the H-terminated Si(001) surface

We present a facile method for the self-directed growth of 1D molecular lines on the H-terminated Si(001) surface. Instead of a previously employed single dangling bond, we here employ a single H-free Si dimer as a reaction site, resulting in an enhanced stability of the radical intermediate for the O-phthalaldehyde (OP) molecule containing two carbonyl groups. This radical intermediate easily abstracts two H atoms from a neighboring Si dimer, thereby allowing the chain reaction for a 1D molecular line. Such a fabricated OP line will be stable at higher temperatures compared to previously reported alkene lines because of its enhanced stability.     

Investigation of proton-proton short-range correlations via the 12C(e,e'pp) reaction

We investigated simultaneously the 12C(e,e'p) and 12C(e,e'pp) reactions at Q2=2 (GeV/c)2, xB=1.2, and in an (e, e'p) missing-momentum range from 300 to 600 MeV/c. At these kinematics, with a missing momentum greater than the Fermi momentum of nucleons in a nucleus and far from the delta excitation, short-range nucleon-nucleon correlations are predicted to dominate the reaction. For (9.5+/-2)% of the 12C(e,e'p) events, a recoiling partner proton was observed back-to-back to the 12C(e,e'p) missing-momentum vector, an experimental signature of correlations.     

Josephson-vortex-flow terahertz emission in layered high-Tc superconducting single crystals

We report on the successful terahertz emission (0.6-1 THz) that is continuous and tunable in its frequency and power, by driving Josephson vortices in resonance with the collective standing Josephson plasma modes excited in stacked Bi2Sr2CaCu2O8+x intrinsic Josephson junctions. Shapiro-step detection was employed to confirm the terahertz-wave emission. Our results provide a strong feasibility of developing long-sought solid-state terahertz-wave emission devices.     

Three-dimensional viscoelastic simulation of coextrusion process: comparison with experimental data

 Three-dimensional numerical simulation of viscoelastic coextrusion process has been performed and numerical results were compared with the experimental data of Karagiannis et al. (1990). By varying the magnitude of the second normal stress difference and its ratio of Fluid I and Fluid II, we were able to control the interface profile and the degree of encapsulation along the downstream direction. By increasing the parameter α (α_Fluid I=α_Fluid II) from 0.1 to 0.4 in the Giesekus model and increasing the α ratio (α_Fluid Iα_Fluid II) between Fluid I and Fluid II from 2.0 to 4.0 in the permissible range of realistic polymeric systems, the interface profile and the degree of encapsulation along the downstream direction were fitted with the experimental results. There was little difference between the numerical results and the experimental data in the interface profile and the degree of encapsulation along the downstream direction when the α ratio was set to 3.0 (0.3:0.1). Fluid I with larger magnitude of the second normal stress difference protrudes into Fluid II with smaller magnitude of the second normal stress difference around the symmetric plane, while Fluid II wraps around Fluid I near the side walls. As the ξ ₁ ratio (ξ _{1 ,Fluid I}ξ _{1 ,Fluid II}) increases from 1.0 to 3.0 for the two-mode Phan-Thien and Tanner model, it was found that the curvature of the interface profile increased, and the difference between the numerical results and the experimental data in the interface profile and the degree of encapsulation along the downstream direction was almost negligible when the ξ ₁ ratio was set to 3.0 (0.54:0.18). Although the parameters of viscoelastic models were fitted by using the shear viscosity data only, quantitative agreements between the numerical results and the experimental coextrusion data were quite satisfactory. Received: 24 April 2001 Accepted: 5 June 2001     

Strain hardening behavior of polymer blends with fibril morphology

We investigate the rheological behavior of the polymer blends with fibril morphology, with special focus on the effect of fibril morphology on the extensional properties under uniaxial extension. We add a small amount of the dispersed phase to the matrix, and control the blend morphology by changing the viscosity ratio. When the fibril morphology is maintained, the blend shows not only a significant increase of the extensional viscosity but the strain hardening behavior. The extensional viscosity increases depending on the aspect ratio of the fibers, while the strain hardening behavior originates from the restricted stretching of deformable fibers, which has been confirmed theoretically by introducing the concept of rigidity of the fiber. It suggests a way to induce the strain hardening behavior by introducing deformable fibrils into the matrix, that is, by the design of polymer blends with a small amount of dispersed phase such that the fibril structure is maintained.     

Conductivity‐Dependent Completion of Oxygen Reduction on Oxide Catalysts

The electric conductivity‐dependence of the number of electrons transferred during the oxygen reduction reaction is presented. Intensive properties, such as the number of electrons transferred, are difficult to be considered conductivity‐dependent. Four different perovskite oxide catalysts of different conductivities were investigated with varying carbon contents. More conductive environments surrounding active sites, achieved by more conductive catalysts (providing internal electric pathways) or higher carbon content (providing external electric pathways), resulted in higher number of electrons transferred toward more complete 4e reduction of oxygen, and also changed the rate‐determining steps from two‐step 2e process to a single‐step 1e process. Experimental evidence of the conductivity dependency was described by a microscopic ohmic polarization model based on effective potential localized nearby the active sites.     

Dually Electroactive Disulfide‐Confined Aryldiazonium Salt Used as a Linker Molecule for Preparing Immunosensor Platforms

A new electroactive disulfide‐confined aryl diazonium (DSAD) salt was synthesized and used as a linker for biomolecules immobilization to prepare two kinds of immunoassay platforms. DSAD was electrodeposited on ITO electrode surfaces by cyclic voltammetry. Disulfide group of DSAD attached on the surfaces were electrochemically oxidized into thiosulfinate or thiosulfonate groups. For the first work, a detection of rabbit antigen was performed on ITO microelectrodes array by spatially‐selective approach. In the second work, DSAD was deposited on electrochemically reduced graphene oxide‐modified ITO surfaces, which were used as a platform for electrochemical sandwich immunoassay for detecting mouse antigen.     

Scoparone interferes with STAT3-induced proliferation of vascular smooth muscle cells

Scoparone, which is a major constituent of Artemisia capillaries, has been identified as an anticoagulant, hypolipidemic, vasorelaxant, anti-oxidant and anti-inflammatory drug, and it is used for the traditional treatment of neonatal jaundice. Therefore, we hypothesized that scoparone could suppress the proliferation of VSMCs by interfering with STAT3 signaling. We found that the proliferation of these cells was significantly attenuated by scoparone in a dose-dependent manner. Scoparone markedly reduced the serum-stimulated accumulation of cells in the S phase and concomitantly increased the proportion of cells in the G0/G1 phase, which was consistent with the reduced expression of cyclin D₁, phosphorylated Rb and survivin in the VSMCs. Cell adhesion markers, such as MCP-1 and ICAM-1, were significantly reduced by scoparone. Interestingly, this compound attenuated the increase in cyclin D promoter activity by inhibiting the activities of both the WT and active forms of STAT3. Similarly, the expression of a cell proliferation marker induced by PDGF was decreased by scoparone with no change in the phosphorylation of JAK2 or Src. On the basis of the immunofluorescence staining results, STAT3 proteins phosphorylated by PDGF were predominantly localized to the nucleus and were markedly reduced in the scoparone-treated cells. In summary, scoparone blocks the accumulation of STAT3 transported from the cytosol to the nucleus, leading to the suppression of VSMC proliferation through G1 phase arrest and the inhibition of Rb phosphorylation. This activity occurs independent of the form of STAT3 and upstream of kinases, such as Jak and Src, which are correlated with abnormal vascular remodeling due to the presence of an excess of growth factors following vascular injury. These data provide convincing evidence that scoparone may be a new preventative agent for the treatment of cardiovascular diseases.     

Analyses of the TCR repertoire of MHC class II-restricted innate CD4+ T cells

Analysis of the T-cell receptor (TCR) repertoire of innate CD4⁺ T cells selected by major histocompatibility complex (MHC) class II-dependent thymocyte–thymocyte (T-T) interaction (T-T CD4⁺ T cells) is essential for predicting the characteristics of the antigens that bind to these T cells and for distinguishing T-T CD4⁺ T cells from other types of innate T cells. Using the TCR^mini Tg mouse model, we show that the repertoire of TCRα chains in T-T CD4⁺ T cells was extremely diverse, in contrast to the repertoires previously described for other types of innate T cells. The TCRα chain sequences significantly overlapped between T-T CD4⁺ T cells and conventional CD4⁺ T cells in the thymus and spleen. However, the diversity of the TCRα repertoire of T-T CD4⁺ T cells seemed to be restricted compared with that of conventional CD4⁺ T cells. Interestingly, the frequency of the parental OT-II TCRα chains was significantly reduced in the process of T-T interaction. This diverse and shifted repertoire in T-T CD4⁺ T cells has biological relevance in terms of defense against diverse pathogens and a possible regulatory role during peripheral T-T interaction.