Electronic structure and polymerization of a self-assembled monolayer with multiple arene rings

We find evidence of intermolecular interactions for a self-assembled monolayer (SAM) formed from a large molecular adsorbate, [1,1′;4′,1′′-terphenyl]-4,4′′-dimethanethiol, from the dispersion of the molecular orbitals with changing wave vector k. With the formation self-assembled molecular (SAM) layer, the molecular orbitals hybridize to electronic bands, with indications of significant band dispersion of the unoccupied molecular orbitals. The electronic structure is also seen to be dependent upon temperature, and cross linking between the neighbor molecules, indicating that the electronic structure may be subtly altered by changes in molecular conformation and packing

The anomalous stiffness of biphenydimethyldithiol

Although organic adsorbates and thin films are generally regarded as soft materials, the effective Debye temperature, indicative of the dynamic motion of lattice normal to the surface, can be very high. For biphenyldimethyldithiol, the effective Debye temperature, determined from core level photoemission from the all carbon arene rings, is comparable to that of graphite. We associate this rigidity to the stiffness of the benzene rings, and the ordering in the molecular thin film. Measurements on the sulfur of poly(hexylthiophene) show that sulfur in an arene ring is less dominated by soft modes than the pendant sulfur of biphenyldimethyldithiol on the time scale of photoemission. ©2005 American Institute of Physic

A study of magnetic interactions of Ni\u3csub\u3e80\u3c/sub\u3eFe\u3csub\u3e20\u3c/sub\u3e arrays using ultrasensitive microcantilever torque magnetometry

We have successfully fabricated single and paired 300 nm×1.5 µm×32 nm Ni80Fe20 bars on a microcantilever using focused ion beam milling. Magnetic interactions of the paired bars were studied by using magnetic force microscopy, microcantilever torque magnetometry, and micromagnetic simulation. Our results clearly indicate that the magnetic switching behavior of the paired Ni80Fe20 bars is affected by magnetostatic interactions. The magnetic hysteresis curves for a sample with eight pairs of Ni80Fe20 bars consist of a series of stable switching states that are related to the domain wall motion in the bars

Stress State Analysis of Iosipescu Shear Specimens for Aerogel Composite with Different Properties in Tension and Compression

AbstractThe objective of present research is to establish guidelines for preparing shear tests of ceramic-fiber-reinforced aerogel. The aerogel composite prepared by Sol-gel methods exhibits bi-modulus properties under tension and compression loadings. Bi- modulus constitutive model of the aerogel composite was built, and then verified by analysis of bending test. Finite element analysis (FEA) was presented on Iosipescu specimens with different V-notch and Round-notch configurations. Several trends have become evident: stress state of bi-modulus aerogel is different from that of isotropic material; stress concentration is a strong function of V-notch tip radius, and increasing V-notch tip radius can effectively reduce normal stress concentration at notch tips; shear stress distribution in the test region can be modified by varying notch angle when V-notch tip radius≤1.3mm; increasing the Round-notch radius can also effectively reduce the normal stress concentration at notch tips. Based on these observations, Round-notch specimen seems to be a favorable choice for reducing the normal stress concentration at notch tips, especially the longitudinal tensile stress concentration. Round-notch specimen with r=4mm is favorable for the uniformly distributed shear stress in the test region. Digital image correlation (DIC) was suggested for shear strain measuring

Isospin effects on the GDR in Vlasov Method

The systematics of the isovector Giant Dipole Resonance (GDR) is studied via the microscopic semi-classical Vlasov method. The calculated results of the peak energy and the widths (FWHM) of the GDR strength distribution can reproduce the experimental data and follow the empirical formula. The isospin effects on the peak energy and the widths of the GDR strength distribution are found small and these effects increase slightly with the $(N-Z)/A$. The characteristics of the GDR have been studied as a function of the temperature in very heavy compound systems $(A>300)$. The interplay between one-body damping and two-body damping is also discussed