Structure and Reactivity of Iron(0)-Phenyltellurolate [PPN][PhTeFe(CO)4]

Anionic iron(0) tetracarbonyl with terminal phenyltellurolate ligand PhTe^?, [PhTeFe(CO)₄]^?, has been synthesized and characterized. The title compound was obtained by addition of (PhTe)₂ to [PPN][HFe(CO)₄] THF solution dropwise. [PPN][PhTeFe(CO)₄] crystallizes in the monoclinic space group C c, with a = 16.119(4) Å, b = 13.141(3) Å, c = 19.880(8) Å, β = 93.04(3)°, V = 4205(2) ų, and Z = 4. The [PhTeFe(CO)₄]^? anion is a trigonal-bipyramidal complex in which the phenyltellurolate ligand occupies an axial position with Fe-Te bond length 2.630(5) Å and the Fe-Te-C(Ph) angle is 103.4(5)°. The neutral iron(0)-telluroether compound, (PhTeMe)Fe(CO)₄, was prepared by alkylation of the [PhTeFe(CO)₄]^?. Protonation of [PhTeFe(CO)₄]^?and reaction of H₂Fe(CO)₄ and PhTe)₂ ultimately lead to formation of the known dimer Fe₂(μ-TePh)₂(CO)₆ and H₂.     

Time-resolved spectroscopy of energy transfer and trapping upon selective excitation in membranes of Heliobacillus mobilis at low temperature

Transient absorption difference spectra in the Qy absorption band of bacteriochlorophyll (BChl) g and in the 670 nm absorption band of the primary acceptor A0 in membranes of Heliobacillus mobilis (Hc. mobilis) were measured at 20 K upon selective excitation at 668, 793, 810, and 815 nm with a 5 nm spectral bandwidth. When excited at 793 nm, the spectral equilibration of excitations from shorter to longer wavelength-absorbing pigments occurred within 3 ps and mostly localized at the band centered around 808 nm. When excited at 668 nm, the excitation energy transfer from the 670 nm absorbing pigment to the Qy band of BChl g took less than 0.5 ps, and the energy redistribution occurred and localized at 808 nm as in the case of the 793 nm excitation. All of the excitations were localized at the long wavelength pigment pool centered around 810 or 813 nm when excited at 810 or 815 nm. A slower energy transfer process with a time constant of 15 ps was also observed within the pool of long wavelength-absorbing pigments upon selective excitation at different wavelengths as has been observed by Lin et al. (Biophys. J. 1994, 67, 2479) when excited at 590 nm. Energy transfer from long wavelength antenna molecules to the primary electron donor P798 followed by the formation of P+ took place with a time constant of 55-70 ps for all excitations. Direct excitation of the primary electron acceptor A0, which absorbed at 670 nm, showed the same kinetic behavior as in the case when different forms of antenna pigments were excited in the Qy region. This observation generally supports the trapping-limited case of energy transfer in which the excitations have high escape probability from the reaction center (RC) until the charge separation takes place. Possible mechanisms to account for the apparent "uphill" energy transfer from the long wavelength antenna pigments to P798 are discussed.     

Staged Development of Modified Silicon Dioxide Films

The hydrolytic generation of SiO₂ films from chlorosilanes or alkoxysilanes is interrupted by incorporating labile organic groups which stop SiO₂ formation at a processable prepolymer stage. The monomers for the prepolymer have electron withdrawing substituents in the -position. The organic groups are removed from the prepolymer at low temperature, extruding ethylene. The formation of SiO₂ proceeds by intramolecular condensation of the electronegative substituents which are now in a hydrolytically unstable bond with silicon and hydroxyl groups or ambient moisture. Films of the prepolymer spun onto silicon wafers are converted into uniform SiO₂-rich films at temperatures between 150–400°C.     

Crystallization behavior and morphological development of isotactic polypropylene blended with nanostructured polyhedral oligomeric silsesquioxane molecules

The thermal properties and morphological development of isothermally crystallized isotactic polypropylene (iPP) blended with nanostructured polyhedral oligomeric silsesquioxane (POSS) molecules at very small loading of POSS were studied with differential scanning calorimeter (DSC), thermal gravimetric analysis, dynamic mechanical analysis, polarized optical microscopy (POM), and wide‐angle X‐ray diffraction (WAXD). The result of DSC indicated that the crystallization rate of iPP increases with the increase in POSS contents during crystallization; moreover, the melting temperature of iPP/POSS nanocomposites slightly decreases, while the heat of fusion increases with the addition of POSS molecules at melting and remelting traces. The storage modulus and thermal stability, respectively, remarkably decrease, while the glass transition temperature of isothermally crystallized iPP/POSS nanocomposites increases slightly with the increase in POSS contents. The morphologies results of WAXD and POM show that the POSS molecules form about 35 nm sized nanocrystals and aggregate to form thread‐like and network structure morphologies, respectively, in the molten state even when the POSS content is very small. These results, therefore, suggest that the interaction force between the POSS molecules should be larger than the force between POSS molecules and iPP matrix; however, those interactions depend on the chain length of functionalized substituents on the POSS cage. Therefore, the POSS molecules aggregate forming nanocrystals and act as an effective nucleating agent for iPP and influence the thermal properties of iPP/POSS nanocomposites due to the shorter chain length of functionalized substituents, methyl, on the POSS cage. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2122–2134, 2006     

Reserve capacity of signal-controlled road network

For a signal control road network subject to equilibrium flows, the maximum possible increase in travel demands is considered in this paper. Using the concept of reserve capacity of signal-controlled junctions, the problem of finding the maximum increase in traffic demands can be formulated as a mathematical program with equilibrium constraints (MPEC). In this paper, we present a projected gradient approach to obtain the maximum increase in travel demands based on the TRANSYT traffic model. Numerical computations are made on a grid network where good results are obtained.     

Advance in next Century nanoCMOSFET research

It is well known that Taiwan's IC industry is in the very leading front of the world, and production of 65 nm devices was launched in 2006. Within a few years, the need of high-k dielectrics and metal gates is eminent and truly indispensable. Professor H.L. Hwang (the author) organized 12 professors and 50 graduate students of National Tsing Hua University and Chiao Tung University, and executed this particular project, which is sponsored by the Ministry of Economic Affairs of Republic of China, and is aimed at treating efficiently this problem and transferred the critical technologies to industry in a time frame of 3 years.     

Scalable and Systolic Architecture for Computing Double Exponentiation Over GF(2 m )

Double-exponentiation is a crucial arithmetic operation for many cryptographic protocols. Several efficient double-exponentiation algorithms based on systolic architecture have been proposed. However, systolic architectures require large circuit space, thus increasing the cost of the protocol. This would be a drawback when designing circuits in systems requiring low cost and low power consumption. However, some cost savings can be attained by compromising speed, as in portable devices and many embedded systems. This study proposes a scalable and systolic AB ² and a scalable and systolic A × B, which are the core circuit modules of double-exponentiation. A scalable and systolic double-exponentiation can thus be obtained based on the proposed scalable AB ² and A × B architecture. Embedded system engineers may specify a target double-exponentiation with appropriate scaling systolic circuits. The proposed circuit has lower circuit space/cost and low time/propagation than other circuits.     

Nanoscale deformation measurement by using the hybrid method of gray-level and holographic interferometry

This study extends the use of holographic interferometry to measure the nanoscale out-of-plane displacement with high surface resolution. It is noted that if the deformation is less than half of the optical wavelength, it is hard to find an obvious fringe pattern. Under such a situation, in general, the phase shift method is used. However, it needs to take more than 3 images for phase shifting and phase reconstruction In this paper, a more simple hybrid method of gray-level and holographic interferometry is used to extract fringe skeletons, in which it just needs to take one or two images for the normal deformation measurement directly, even if there exists no obvious fringe pattern. The displacement field with high surface resolution can also be obtained. The proposed method yielded a theoretical precision of 0.15 nm for out-of-plane displacement with a monochromatic CCD camera of 10-bit gray scale (1024 gray scales) sensitivity and microscale surface resolution for millimeter scale object with 640×480 pixels image resolution by an He–Ne LASER (632.8 nm wavelength) light source. The gray-level method is proposed to calculate the non-obvious interferometry fringe by traditional holographic interferometry hologram, and the result showed that this method works for this purpose.     

Electronic Structure of EuMo6Se8 Studied by X-Ray Absorption Spectroscopy

The rare-earth based molybdenum chalcogenides, REMo₆Se₈ (RE = rare-earth metals) have been extensively studied because of their unique crystal structure based on Mo₆Se₈ clusters and their outstanding properties involving coexistence of superconductivity and magnetism. Among all these compounds, Ce and Eu based chalcogenides are magnetic and non-superconductors and possess many novel properties. Understanding their electronic structure is likely to provide valuable information about these materials. We employ X-ray absorption near-edge structure (XANES) spectroscopy at Mo and Se K-edges of EuMo₆Se₈ to identify the local environment respectively around Mo and Se ions and XANES spectra at L₃-edge of Eu ion to identify their valence state. Results from this study demonstrate that Se ions in EuMo₆Se₈ are in two inequivalent sites and the valency of Eu is divalent.     

Crystallinity and electrical properties of (Pb,Sr)TiO<Subscript>3</Subscript> films enhanced by laser-assisted low-thermal-budget annealing

The physical and electrical properties of (Pb,Sr)TiO₃ (PSrT) films annealed by various techniques are systematically investigated in this study. The crystallinity and ferroelectricity of PSrT films can be enhanced by excimer laser annealing (ELA), but the effect only works on the upper region of films. On the other hand, PSrT films treated by rapid thermal annealing (RTA) can also improve crystallinity and ferroelectricity. However, the leakage current of films is seriously increased due to defects and interfacial diffusion induced by post-RTA at high temperature. As a result, the laser-assisted two-step annealing (post-ELA+RTA) is proposed in this work. It is found that PSrT films treated by post-ELA+RTA show improved crystallinity, better ferroelectric properties, higher dielectric constant, and lower leakage currents, which bring out the longer lifetime and higher breakdown field. PACS 77.84.-s; 81.40.Ef; 42.62.-b