Femtosecond pump and probe experiments on thiophene-based polymersby a hybridly mode-locked cavity-dumped dye laser

Results on the bleaching decay observed in low-band gap thiophene-based polymers by femtosecond pump and probe experiments are presented. The laser used for excitation and probe is a newly developed cavity dumped femtosecond dye laser. The excited state kinetics of these materials presents a fast biexponential time behavior that may be related to the formation and decay of self-trapped excitons     

Study of yeast DNA topoisomerase II and its truncation derivatives by transmission electron microscopy

The 1429-amino acid residue long yeast DNA topoisomerase II and three of its deletion derivatives, a C-terminal truncation containing residues 1-1202, a 92-kDa fragment spanning residues 410-1202, and an A'-fragment spanning residues 660-1202, were examined by transmission electron microscopy. Analysis of rotary-shadowed images of these molecules shows that the full-length enzyme assumes a tripartite structure, in which a large globular core comprising the carboxyl parts of the dimeric enzyme is connected to a pair of smaller spherical masses comprising the ATPase domains of the enzyme. The linkers bridging the large globular structure and each of the smaller spheres are not visible in most of the images but appear to be sufficiently stiff to keep the relative positions of the connected parts. The angle extended by the pair of spherical masses is variable and falls in a range of 50-100 degrees for the majority of the images. On binding of a nonhydrolyzable ATP analog to the enzyme, this angle is significantly reduced as the two spherical masses swing into contact. These observations, together with results from previous biochemical and x-ray crystallographic studies of the enzyme, provide a sketch of the molecular architecture and conformational states of a catalytically active type II DNA topoisomerase.     

Suppression of corner effects in wide-channel triple-gate bulk FinFETs

This paper presents a method of eliminating corner effects in triple-gate bulk FinFETs. The parasitic device in FinFET’s corners can be turned off by increasing body doping in corner regions by corner implantation. Corner implantation described in this work does not require additional masks, rotation or tilt. This method is investigated in idealized (with rectangular cross-section of the fin) and realistic (with rounded top corners of the fin) triple-gate bulk FinFETs and has shown considerable improvements: kink effect in transfer characteristics is completely eliminated, threshold voltage increased by up to 0.43 V, subthreshold swing and drain-induced barrier-lowering decreased to values under 95 mV/dec and 16 mV/V, respectively. Optimization is performed on the realistic rounded-corner FinFET structure to find the proper body doping and corner implantation peak values for acceptable threshold voltage and on-state current.     

Modeling the fabrication process of micropatterned macromolecular scaffolds for peripheral nerve regeneration

Tubular scaffolds demonstrated to be able to reconnect the proximal and distal stumps of transected peripheral nerves and induce regeneration of the lost nerve trunk. Recently, a spinning technique has been developed, able to produce tubular collagen‐based scaffolds characterized by a radially patterned microporosity. The technique is based on the centrifugal sedimentation of collagen taking place when a cylinder, containing an aqueous collagen suspension, is rotated rapidly around its axis. In this work, the centrifugation process was modeled by means of the Lamm differential equation for collagen concentration, with the assumption that sedimentation and diffusion coefficients were dependent on the local concentration, according to appropriate scaling laws. With such assumptions, the model was able to predict the actual tube formation and its inner radius, in good agreement with the experimental results. The possibility to predict the final scaffold inner diameter as a function of the processing parameters has a fundamental importance for the set up of a precise fabrication method, which does not make use of any complex mold. This would significantly reduce the production complexity and the extent of scaffold manipulation during production, resulting in a cleaner production process and safety of the device. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microwave Cavity Perturbation as a Tool for Laboratory In Situ Measurement of the Oxidation State of Three Way Catalysts

Three-way catalyst-based automotive exhaust gas aftertreatment is of high importance to meet today’s emission standards. To determine in situ the oxygen loading state of three-way catalysts, a microwave cavity perturbation method is used. In this study, it is investigated whether this measurement setup that had originally been described for full-sized catalysts can be transferred to a lab test bench using cores of 1″ diameter. The initial tests were successful and a high correlation between the oxygen loading degree dependent resonance frequency and the conversion was found. As an application example of the new in situ characterization technique, the steady state degree of oxidation of a three way catalyst was measured as a function of the exhaust stoichiometry. The experimental results are compared with the prediction of a recently published improved kinetic model that takes into account the oxidation of reduced ceria by H₂O and CO₂. It is shown that the experimental observations agree very well with this improved model. This result provides evidence that under typical operating conditions, the degree of oxidation of the three way catalyst is controlled by equilibrium effects.     

Enhancing Light Emission in Interface Engineered Spin‐OLEDs through Spin‐Polarized Injection at High Voltages

The quest for a spin‐polarized organic light‐emitting diode (spin‐OLED) is a common goal in the emerging fields of molecular electronics and spintronics. In this device, two ferromagnetic (FM) electrodes are used to enhance the electroluminescence intensity of the OLED through a magnetic control of the spin polarization of the injected carriers. The major difficulty is that the driving voltage of an OLED device exceeds a few volts, while spin injection in organic materials is only efficient at low voltages. The fabrication of a spin‐OLED that uses a conjugated polymer as bipolar spin collector layer and ferromagnetic electrodes is reported here. Through a careful engineering of the organic/inorganic interfaces, it is succeeded in obtaining a light‐emitting device showing spin‐valve effects at high voltages (up to 14 V). This allows the detection of a magneto‐electroluminescence (MEL) enhancement on the order of a 2.4% at 9 V for the antiparallel (AP) configuration of the magnetic electrodes. This observation provides evidence for the long‐standing fundamental issue of injecting spins from magnetic electrodes into the frontier levels of a molecular semiconductor. The finding opens the way for the design of multifunctional devices coupling the light and the spin degrees of freedom.     

Exploiting Unique Alignment of Cobalt Ferrite Nanoparticles,Mild Hyperthermia,and Controlled Intrinsic Cobalt Toxicity for Cancer Therapy

Nanoparticle-based magnetic hyperthermia is a well-known thermal therapy platform studied to treat solid tumors, but its use for monotherapy is limited due to incomplete tumor eradication at hyperthermia temperature (45 °C). It is often combined with chemotherapy for obtaining a more effective therapeutic outcome. Cubic-shaped cobalt ferrite nanoparticles (Co–Fe NCs) serve as magnetic hyperthermia agents and as a cytotoxic agent due to the known cobalt ion toxicity, allowing the achievement of both heat and cytotoxic effects from a single platform. In addition to this advantage, Co–Fe NCs have the unique ability to form growing chains under an alternating magnetic field (AMF). This unique chain formation, along with the mild hyperthermia and intrinsic cobalt toxicity, leads to complete tumor regression and improved overall survival in an in vivo murine xenograft model, all under clinically approved AMF conditions. Numerical calculations identify magnetic anisotropy as the main Co–Fe NCs’ feature to generate such chain formations. This novel combination therapy can improve the effects of magnetic hyperthermia, inaugurating investigation of mechanical behaviors of nanoparticles under AMF, as a new avenue for cancer therapy.     

An Experimental and Computational Modeling Study on Additively Manufactured Micro-Architectured Ti–24Nb–4Zr–8Sn Hollow-Strut Lattice Structures

Herein, the design, manufacturing, and mechanical testing of hollow-strut lattice structures of the metastable β-titanium alloy Ti–24Nb–4Zr–8Sn (Ti2448) are performed. Due to the absence of studies in the literature, this study focusses on two important aspects: 1) the designing of micro-architectured lattice structures and 2) metastable β-titanium alloy. Face-centered cubic (FCC) and body-centered cubic (BCC) hollow-strut lattices are designed by computer-aided design and manufactured by laser powder bed fusion. The microstructure of the hollow lattices shows plates of α″-martensite phase within the β phase. The FCC hollow lattice structure shows higher tensile strength compared to the BCC hollow lattice structure, while the load-bearing capability of the FCC hollow lattice structure is lower than that of the BCC hollow lattice structure. At lower strains, the tensile force-displacement curve of the hollow lattice structure matches the simulated tensile force-displacement curve. At higher strains, a large deviation in the force-displacement curve is observed in the hollow lattices.     

Some properties of solutions of the semi-state model for nonlinear nonstationary systems

Certain properties of solutions similar to set invariance, set attractivity, boundedness, BIBO stability, etc. are investigated for the semistate model $$P(t)\dot x = M(t,x)x + D(t,x)u,y = q(t,x,u).$$ For systems considered, it is assumed that the reduction to a normal form of lower order is not possible. Using the direct method of Liapunov, the properties of solutions are investigated without actual knowledge of solutions.