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The electronic structures and optical properties of cubic ZrO 2 are investigated by means of generalized gradient approximation (GGA) + U approach. By including the Coulomb interaction of 4 d orbitals on Zr atom ( U d ), as well as of 2 p orbitals on O atom ( U p ), the experimental value of the band gap can be reproduced when U d =8.25 eV, and U p =4.6 eV. With these U values, the electronic structure and optical properties are calculated, in comparison to experiments and other theoretical results, e.g., by scissor operations. Our results are found to be in good agreement with available experimental data, and more accurate than those obtained by a scissor operation.

A di-nuclear compound, [(CoTPA)2(1,4-BQ)][AsF6]3 (1) (TPA = tris(2-pyridylmethyl)amine, 1,4-BQ = deprotonated 2,5-dihydroxy-1,4-benzoquinone), was formed by one electron oxidation of [(CoTPA)2(1,4-BQ)]2+ cations. The compound was characterized by X-ray diffraction, electrochemistry, ESR, thermal- and photo-induced magnetic measurements. Variable temperature magnetic measurements have demonstrated that valence tautomeric transition with a small hysteresis around room temperature and photo-excited phenomenon is exhibited. In addition, temperature-dependent hs–ls relaxation of the converted high-spin fraction after irradiation was also studied.

The LaFeO 3 modified by silver (Ag–LaFeO 3 ) further modified by single-walled carbon nanotubes (SWCNTs–Ag–LaFeO 3 ) with different weight ratio were prepared using a sol–gel method combined with the microwave chemical synthesis. The phase structures and micro-morphology of SWCNTs–Ag–LaFeO 3 were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. Indirect-heating sensors using SWCNTs–Ag–LaFeO 3 sensitive materials were fabricated on an alumina tube with Au electrodes and platinum wires. Gas-sensing characteristic of SWCNTs–Ag–LaFeO 3 to formaldehyde was investigated. It is found that the structure of SWCNTs–Ag–LaFeO 3 is of orthogonal perovskite. The gas-sensing properties of the Ag–LaFeO 3 sample modified by SWCNTs with 0.75% weight ratio (0.75%SWCNTs–Ag–LaFeO 3 ) are the best. The response of 0.75%SWCNTs–Ag–LaFeO 3 powder to 0.5 ppm formaldehyde is 23 at 86 °C. The detect limit to formaldehyde is 0.2 ppm. The response and recovery times are 6 s and 20 s, respectively. Those good properties make them the promising candidates for practical detectors to formaldehyde.

The gas-sensing properties of silver doped lanthanum ferrite (Ag–LaFeO 3 ) compounds for formaldehyde were investigated in this paper. Ag–LaFeO 3 powders were prepared using sol–gel method combined with microwave chemical synthesis. The powders were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The formaldehyde gas-sensing characteristics for the sample were examined between 65 °C and 220 °C. The experimental results indicate that the sensor based on the sample Ag–LaFeO 3 shows excellent gas-sensing properties to formaldehyde gas and the operating temperature is very low. At the optimal operating temperature of 90 °C, the response of the sensor based on Ag–LaFeO 3 to 1 ppm formaldehyde is 25, while to other test gases, the response is all lower than 6. With increasing concentration of formaldehyde, the resistance of the sensor based on the sample Ag–LaFeO 3 increases. The response and recovery times for the sample to formaldehyde gas are 65 s and 60 s, respectively.

A new mononuclear Fe(III)–catecholate complex, which exhibits an incomplete spin transition without hysteresis, had been synthesized and structurally characterized. Analyzed from the structural characteristics, the tripodal ligand must play the important role in affecting the spin crossover (SCO) behavior. The larger steric strain effect and weak cooperativity existed in the crystal lattice are inclined to favor the incomplete transition.

article i nfo Article history: Zirconia coated carbon fiber for thermal and oxidation protection was prepared through a sol-gel technique. A zirconia sol was synthesized with the zirconium oxychloride, ammonia and polyethylene glycol, each of them acting as the zirconium resource, precipitant and surfactant. The morphology, phase composition and thermal properties of the zirconia coated carbon fiber were evaluated by SEM, EDS, XRD and TG-DTA. The increase of dipping cycles can raise the thickness of the coating, while attaching more ZrO2 crystals on the coating surface. Mass variations of the 3 mol% YSZ and 2 mol% YSZ coated carbon fibers at 800 °C are 20% and 40%, less than the 70% of the uncoated carbon fiber.

A new heptanuclear compound [{Co(TPA)CN}6Fe][PF6]8 (1) (TPA = tris(2-pyridylmethyl)amine) was constructed by the reaction of [Co(TPA)]2 + cations and K3Fe(CN)6. The cyanometalate core is capped by six mono-nuclear cobalt units via the cyanides. 1 crystallizes in triclinic space group C2 with a = 19.5720 A, b = 26.2450 A, c = 16.3820 A, β = 118.500° and Z = 2. Variable temperature magnetic measurements have demonstrated that very weak antiferromagnetic interaction between the nearest paramagnetic CoII centers is exhibited. Thus weak antiferromagnetic coupling might be transferred by NC Fe CN bridging units.

In this paper, dense short carbon fiber reinforced silicon carbide matrix composites had been fabricated by hot-pressed (HP) sintering using Al2O3 and La2O3 as sintering additives. The results showed that the combination of Al2O3 and La2O3 system was effective to promote densification of short cut carbon fiber reinforced silicon carbide composites (Cf/SiC). The whisker structure of silicon carbide was formed during the annealed treatment at 2023 K for 1 h. However, it was noted that this structure was not observed in the as-received HP material. The mechanism of forming whisker structure was not clear, but this kind of whisker structure was helpful to improve mechanical properties. The combination of grain bridging, crack deflection and whisker debonding would improve the fracture toughness of the Cf/SiC composites.

A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (>75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature.

An optimal fault tolerant control (FTC) scheme using output probability density functions (PDFs) is studied for the general stochastic continuous time systems. Being different from the classical FTC problems, the measured information is the stochastic distribution of the system output rather than its value. The control objective is to use the output PDFs to design control schemes that can compensate the fault and attenuate the disturbance. A multi-layer perceptron (MLP) neural network is applied to approximate the output PDFs, with which nonlinear principal component analysis (NLPCA) can be used to reduce the model order. For the established continuous-time weighting system with disturbances and uncertainties which is used to link the input and the weights, an LMI-based feasible FTC method is presented to assure that the fault can be well measured and compensated, where the H"~ performance index for the uncertain error systems is optimized.

Specific accumulation of radiolabeled antisense oligonucleotides as a result of binding by an antisense mechanism to target mRNAs in tumor has been repeatedly observed. However, the mechanisms responsible for nonspecific cellular accumulation remain almost completely unexplored. We have occasionally observed in cell culture nonspecific accumulations of 99m Tc-labeled sense, scrambled or random control oligonucleotides in tumor cells comparable to or even higher than those of the corresponding antisense oligonucleotides. We have also observed that these nonspecific accumulations of control oligonucleotides are sequence dependent. To explore the influence of base composition on nonspecific accumulation, we used MCF-7 breast cancer cells, along with 10 uniform phosphorothioates and 5 uniform phosphodiesters oligonuc leotides. Three of the phosphorothioates were antisense against different sites within the survivin mRNA, and two were the corresponding sense and scrambled controls. In addition, the accumulations in MCF-7 cells of radiolabeled poly A, poly C, poly T and poly GGGA phosphorothioate oligonucleotides were also studied to explore the influence of each nitrogenous base on the nonspecific cell accumulations of phosphorothioate oligonucleotides. Our results show that guanine content is an important determinant of nonspecific cellular accumulations under the conditions of this investigation. If this observation can be shown to be universally applicable to other cell types, then the selection of control sequences in studies of antisense tumor targeting should avoid those that are guanine rich, if possible.

The attempt to target the limited copies of messenger RNA (mRNA) in vivo with radiolabeled nucleobase oligomers as antisense probes is challenging. Selecting an antisense molecule with superior properties, enhancing the cellular kinetics, and improving the radiolabeling chemistry would be the reasonable approach to accomplish this goal. The present study reports a method to construct a chimera of phosphorodiamidate morpholino nucleobase oligomer (MORF) covalently conjugated to a peptide containing a cell membrane transduction Tat peptide and an N 2 S 2 chelator for technetium-99m ( 99m Tc) radiolabeling (N 2 S 2 -Tat-MORF). The radiolabeling properties and cellular kinetics of 99m Tc-N 2 S 2 -Tat-MORF were measured. As hypothesized, the preparation of 99m Tc-N 2 S 2 -Tat-MORF could be achieved by an instant one-step method with labeling efficiency greater than 95%, and the 99m Tc-N 2 S 2 -Tat-MORF showed distinct properties in cell culture from those of a control, the same MORF sequence without Tat but with mercaptoacetyltriglycine (MAG 3 ) as chelator for 99m Tc ( 99m Tc-MAG 3 -MORF). 99m Tc-N 2 S 2 -Tat-MORF achieved maximum accumulation of about 35% within 2 h, while 99m Tc-MAG 3 -MORF showed lower and steadily increasing accumulations but of less than 1% in 24 h. These preliminary results demonstrated that the proposed chimera has properties for easy labeling, and 99m Tc-N 2 S 2 -Tat-MORF prepared by this method possesses enhanced cellular kinetics and merits further investigation for in vivo mRNA targeting.

Technetium-99m labeled ubiquicidin peptide 29-41 ((99m)Tc-UBI) is a cationic human antimicrobial peptide fragment that has been shown to bind bacteria in vitro and accumulates at sites of infection in experimental animals. To help determine if (99m)Tc-UBI is bound to the bacterial cell envelope by a simple nonspecific electrostatic interaction, a comparative study of the in vitro binding of (99m)Tc-UBI and two different (99m)Tc labeled cationic peptides ((99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr) to bacteria and to two tumor cell line (LS174T and ACHN) was performed. The in vivo specificity of (99m)Tc-UBI for infection in mice was also evaluated using dual labels in the same animal and comparing the target/non-target ratio for (67)Ga-citrate and (99m)Tc-UBI at sites of induced infection and sterile inflammation. Under conditions of this study, the in vitro binding of (99m)Tc-UBI, (99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr to S. aureus was 35, 78 and 87% respectively. While the binding of (99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr was 37 and 33% to colon tumor cells (LS174T) and 39 and 41% to renal tumor cells (ACHN) respectively, the binding of (99m)Tc-UBI to both cell types was much lower at less than 4%. In vivo studies revealed that there is a significant difference (p < 0.05) in the radioactive accumulation of (99m)Tc-UBI between the sites of infection and inflammation compared to (67)Ga-citrate. Thus, (99m)Tc-UBI showed an average infection/inflammation ratio of 2.08 +/- 0.49 compared to 1.14 +/- 0.45 for (67)Ga-citrate. In conclusion, the in vitro and in vivo results provide evidence that a specific mechanism is responsible of the (99m)Tc-UBI bacterial intracellular accumulation.

An important limitation restricting antisense nuclear medicine imaging is low radioactivity accumulations in target cells. The Tat peptide (Tat), a basic domain of the HIV Tat protein, has been shown to enhance cell accumulation of various biomolecules. PURPOSE: The influence of Tat, as a cationic carrier, on the accumulation in cell culture of anionic antisense DNAs bound electrostatically rather than covalently was investigated. To establish specificity of the accumulation, antisense DNA and control sequence were studied along with four different peptides. The technique of in situ reverse transcription was used to assay the in vivo hybridization of antisense DNA to the target mRNA in cultured live cells when transducted with the Tat peptide. METHODS: Uniform phosphorothioated DNAs were radiolabeled with 99mTc via Hynic/tricine. This 18 mer antisense DNA against RIα mRNA along with its sense and random control was studied in ACHN cells with the four peptides as carriers. RESULTS: The addition of Tat significantly increased cell accumulations. At 12 hours accumulations went from 14% to 45% for the antisense DNA and from 4% to 12% for control. Furthermore, an antisense effect was again suggested, now with the Tat carrier, by the significantly higher accumulation of 99mTc on both antisense DNAs vs. controls. Moreover, the accumulated antisense DNA enhanced with the Tat carrier was capable of priming reverse transcription as determined by an in situ assay suggesting that the DNA could escape from entrapment in endosome or lysosome vesicles for hybridization. However, differences in cellular accumulation with either Tat compared to either scrambled peptide were not significant, showing that the Tat in this study was functioning merely as a cationic carrier. CONCLUSIONS: Although electrostatic binding of antisense DNA to Tat is convenient, the association may mask the unique transduction properties of the peptide. Nevertheless, a promising improvement in cellular accumulation of antisense DNA was observed through the use of these carriers. In addition, at least a fraction of the transducted DNA appears to be free of entrapment to hybridize to its mRNA target in live cells.

By considering the time variation of band-edge profile arising from the decay of injected charge in quantum wells(QWs), we employ a wave packet method to verify that the actual escape time of certain amount of electrons from QWs could be much larger than that for a single electron. The theoretical result is also in agreement with our measurement of escape time, performed by using a newly developed method--transient current response.