Diffusive limit of a tagged particle in asymmetric simple exclusion processes

Invariance principles are proved under diffusive scaling for the centered position of a tagged particle in the simple exclusion process with asymmetric nonzero drift jump probabilities in dimensions d ≥ 3. The method of proof is by martin‐gale techniques which rely on the fact that symmetric random walks are transient in high dimensions. © 2000 John Wiley & Sons, Inc.     

Synthesis and optical and electrochemical properties of copolymers containing 9,9‐dihexylfluorene and 9‐dimethylaminopropylcarbazole chromophores

Soluble and well‐defined 9,9‐dihexylfluorene and 9‐dimethylaminopropylcarbazole based copolymers PFCN and 5PFCN have been prepared by Suzuki coupling polymerization. For comparison, alternate copolymer of 9,9‐dihexylfluorene and 9‐hexylcarbazole (PFC) was also prepared with the same method. Furthermore, alternate copolymer of 9,9‐dihexylfluorene and 9‐dimethylethylammoniumpropylcarbazole (PFCNE) was prepared from PFCN by the ethylation of its dimethylaminopropyl groups with bromoethane. These copolymers were soluble in organic solvents and showed high glass‐transition temperatures (75–160 °C). The optimized architecture of PFCN from a simulation was a spiral, which was different from the linear structure of poly(9,9‐dihexylfluorene) (PFO). Thermogravimetric analysis showed that the residual weights of 5PFCN, PFCN, PFC, and PFCNE at 800 °C were all greater then 50%, whereas PFO showed complete thermal decomposition. Both the absorption and photoluminescence emission peaks of these copolymers showed blueshifts after the introduction of the carbazole units because of reduced conjugation. Moreover, the introduction of 9‐hexylcarbazole and 9‐dimethylamionpropylcarbazole moieties into copolymers PFC and PFCN, respectively, effectively prevented the excimer formation of PFO. According to cyclic voltammetry results, PFCNE containing quaternary amino pendant groups exhibited the most stable reduction–oxidation cycles. The turn‐on electric fields of their electroluminescence devices decreased with increasing carbazole content because of the more balanced carrier injection. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 3882–3895, 2006     

Economic optimization of off-line inspection with rework consideration

This paper addresses issues relating to off-line inspection with rework consideration. We develop a mathematical model to determine the first unit inspected and the average number to be inspected in a batch, assuming the involvement of a quality-control department with a standard procedure. Numerical analyses are used to simulate the effect of changes in the various parameters on the optimal solution when the probability of a transition between states follows the discrete Weibull distribution.     

Synthesis,photophysics, and electroluminescent performance of stable blue‐light‐emitting copoly(9,9‐diarylfluorene)s

A series of fluorene derivatives containing nonsymmetric and bulky aromatic groups at C‐9 position were synthesized and used for the preparation of blue‐light‐emitting copolyfluorenes ( P1 – P4 ) by the Suzuki coupling polycondensation. The copolymers were characterized by molecular weight determination, elemental analysis, differential scanning calorimeter, thermogravimetric analysis, absorption and emission spectroscopy, cyclic voltammetry, and differential pulse voltammetry. Their decomposition temperatures and glass transition temperatures are 423–441 °C and >120 °C, respectively. In film state, the copolyfluorenes exhibit blue photoluminescence at 425–450 nm, which remains almost unchanged after annealing at 200 °C in air for 60 min. Polymer light‐emitting diodes [ITO/PEDOT:PSS/ P1 – P4 /Ca(50 nm)/Al(100 nm)] show stable blue‐light emission under device operation with the CIE co‐ordinates being between (0.16, 0.07) and (0.17, 0.09). The light‐emitting diodes devices from P1 and P3 containing electron‐deficient oxadiazole units display enhanced performance, with the maximum brightness and maximum current efficiency being (4510 cd/m² and 2.40 cd/A) and (2930 cd/m², 1.19 cd/A), respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2821–2834, 2009     

Photochemical Activities of N‐Nitroso Carboxamides and Sulfoximides and Their Application to DNA Cleavage

N‐Nitroso compounds containing benzene, fluorene or fluorenone rings were synthesized. Photolysis of these compounds with 312‐nm UV light provided the NO ^. species, the presence of which was corroborated by use of an EPR method and of 2‐phenyl‐4,4,5,5‐tetramethylimidazolin‐1‐oxyl 3‐oxide (PTIO) as a trapping agent. During irradiation of N‐methyl‐N‐nitroso‐9‐fluorenone carboxamide ( 14 c ) in the absence of PTIO, it underwent decomposition followed by recombination to give the heterocyclic nitric oxide radical 15 . Incorporation of intercalating moieties endowed the N‐nitroso compounds with DNA‐cleaving ability through single‐strand scission upon UV irradiation in a phosphate buffer (pH 5.0–8.0) under aerobic conditions.     

Design of optimal observers with specified eigenvalues via shifted Legendre polynomials

The quadratic performance measure of estimation errors in approximated by using the Legendre polynomial approach for the design of optimal observers with specified distinct and multiple eigenvalues. This method is simple as compared with other design techniques of optimal observers. One example is illustrated, and only a small number (m=6) of shifted Legendre series are needed to produce a much better result than that obtained by the convenient block-pulse function.     

Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes

The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-independent value 3 at intermediate field but is reduced to about 2 for higher field.     

Biomolecular interactions of selected buffers with hemoglobin

Journal of Thermal Analysis and Calorimetry - To elucidate the influence of commonly used biological buffers on the hemoglobin (Hb) structure, biomolecular interactions between Hb and the selected...     

Crystal Structure Analysis of the Repair of Iron Centers Protein YtfE and Its Interaction with NO

Molecular mechanisms underlying the repair of nitrosylated [Fe–S] clusters by the microbial protein YtfE remain poorly understood. The X‐ray crystal structure of YtfE, in combination with EPR, magnetic circular dichroism (MCD), UV, and ¹⁷O‐labeling electron spin echo envelope modulation measurements, show that each iron of the oxo‐bridged Fe^II–Fe^III diiron core is coordinatively unsaturated with each iron bound to two bridging carboxylates and two terminal histidines in addition to an oxo‐bridge. Structural analysis reveals that there are two solvent‐accessible tunnels, both of which converge to the diiron center and are critical for capturing substrates. The reactivity of the reduced‐form Fe^II–Fe^II YtfE toward nitric oxide demonstrates that the prerequisite for N₂O production requires the two iron sites to be nitrosylated simultaneously. Specifically, the nitrosylation of the two iron sites prior to their reductive coupling to produce N₂O is cooperative. This result suggests that, in addition to any repair of iron centers (RIC) activity, YtfE acts as an NO‐trapping scavenger to promote the NO to N₂O transformation under low NO flux, which precedes nitrosative stress.     

Magnetic nanoparticles for high-sensitivity detection on nucleic acids via superconducting-quantum-interference-device-based immunomagnetic reduction assay

In this work, we investigate the feasibility of detecting quantitatively DNA molecules utilizing the technology named after the immunomagnetic reduction (IMR) assay. Magnetic nanoparticles dispersed in a phosphate buffer saline solution were bio-functionalized with probing single-strand DNA. A superconducting quantum interference device (SQUID) ac magnetosusceptometer was employed to detect IMR signals related to the concentration of the target DNA. The results reveal that use of IMR assay had merits such as a high convenience level, e.g. wash-free processes and high sensitivity, down to pM, for DNA detection.