Synthesis and characterization of novel sulfonated polyimides from 1,4-bis(4-aminophenoxy)-naphthyl-2,7-disulfonic acid

A novel sulfonated diamine monomer, 1,4-bis(4-aminophenoxy)-naphthyl-2,7-disulfonic acid (BAPNDS), was synthesized. A series of sulfonated polyimide copolymers were prepared from BAPNDS, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and nonsulfonated diamine 4,4'-diaminodiphenyl ether (ODA). Flexible, transparent, and mechanically strong membranes were obtained. The membranes displayed slightly anisotropic membrane swelling. The dimensional change in thickness direction was larger than that in planar. The novel SPI membranes showed higher conductivity, which was comparable or even higher than Nafion 117. Membranes exhibited methanol permeability from 0.24 x 10(-6) to 0.80 X 10(-6) cm(2)/s at room temperature, which was much lower than that of Nafion (2 x 10-6 CM2/s). The copolymers were thermally stable up to 340 degrees C. These preliminary results have proved its potential availability as proton-exchange membrane for PEMFCs or DMFCs.

3{1-[2-(-3-羟基-1-甲基-2-亚丁烯氨基)-苯亚氨基]-乙基}4-甲硫基-2,4-戊二烯-2-醇的不对称Schiff碱镍(Ⅱ)配合物的合成、结构和性质

由 5-(2-乙酰基-1-甲硫基-3-羰基-亚丁基)-丙二酸亚异丙酯 (1)与邻苯二胺及乙酸镍()经一步反应合成了3{1-[2-( -3-羟基-1-甲基-2-亚丁烯氨基)-苯亚氨基 ]-乙基} 4-甲硫基-2,4-戊二烯-2-醇(3)的不对称四齿 Schiff碱镍()配合物(2),X射线衍射结果表明,配合物 2属单斜晶系,P21/C空间群.a=1.1476(2)nm,b=1.1782(2)nm,c=1.4810(3)nm;β=111.73(2)°,V=1.8602(7)nm3,Z=4,Rf=0.0535.电化学(循环伏安)测定结果表明,该配合物在测定条件下(阳极峰电位为1.1)发生了不可逆的氧化-还原反应.

Alkali metal ions transfer across a water/1,2-dichloroethane interface facilitated by a novel monoaza-B15C5 derivative

In this paper, a novel monoaza-B15C5 derivative, N-(2-tosylamino)-isopentyl-monoaza-15-crown-5 (L), is used as an ionophore to facilitate alkali metal cations transfer across a water/1,2-dichloroethane (W/DCE) interface. Well-defined voltammetric behaviors are observed at the polarized W/DCE interfaces supported at micro- and nano-pipets except Cs+. The diffusion coefficient of this ionophore in the DCE phase is calculated to be equal to (3.3+/-0.2) x 10(-6) cm(2) s(-1). The experimental results indicate that a 1:1 (metal: ionophore) complex is formed at the interface with a TIC/TID mechanism. The selectivity of this ionophore towards alkali ions follows the sequence Na+ > Li+ > K+ > Rb+ > Cs+. The logarithm of the association constants (log beta(1)(0)) of the LiL+, NaL+, KL+ and RbL+ complexes in the DCE phase are calculated to be 10.6, 11.6, 9.0 and 7.1, respectively. The kinetic parameters are determined by steady-state voltammograms using nanopipets. The standard rate constants (k(0)) for Li+, Na+, K+ and Rb+ transfers facilitated by L are 0.54+/-0.05, 0.63+/-0.09, 0.51+/-0.04 and 0.46+/-0.06 cm s(-1), respectively. The pH values of aqueous solution have little effect on the electrochemical behaviors of these facilitated processes. The results predicate that this new type of ionophore might be useful to fabricate electrochemical sensor of sodium ion.

The role of redox property of La2-x(Sr,Th)(x)CuO4 +/-lambda playing in the reaction of NO decomposition and NO reduction by CO

Two systems of mixed oxides, La2-xSrxCuO4 +/- lambda (0.0 less than or equal to x less than or equal to 1.0) and La(2-x)Tn(x)CuO(4 +/-) (lambda) (0.0 less than or equal to x less than or equal to 0.4), with K2NiF4 structure were prepared. The average valence of Cu ions and oxygen nonstoichiometry (lambda) were determined by means of chemical analysis. Meanwhile, the adsorption and activation of nitrogen monoxide (NO) and the mixture of NO + CO over the mixed oxide catalysts were studied by means of mass spectrometry temperature-programmed desorption (MS-TPD). The catalytic behaviors in the reactions of direct decomposition of NO and its reduction by CO were investigated, and were discussed in relation with average valence of Cu ions, A and the activation and adsorption of reactant molecules. It has been proposed that both reactions proceed by the redox mechanism, in which the oxygen vacancies and the lower-valent Cu ions play important roles in the individual step of the redox cycle. Oxygen vacancy is more significant for NO decomposition than for NO + CO reaction. For the NO + CO reaction, the stronger implication of the lower-valent Cu ions or oxygen vacancy depends on reaction temperature and the catalytic systems (Sr- or Th-substituted). (C) 2000 Elsevier Science B.V. All rights reserved.

Relationship between the structure and catalytic activity of La2-xSrxNiO4-lambda(0<=x<=1) mixed oxides for NH3 oxidation

A series of samples having the composition of La2-xSrxNiO4(0 less than or equal to x less than or equal to 1) were prepared and used as catalysts for NH3 oxidation. It was found that the La and oxygen vacancies exist in the La2-xSrxNiO4-lambda(0 less than or equal to x less than or equal to 1). The unit cell volume decreases with the increase of x. For bath c and a parameters there appeared a turning point at x = 0.5. Doping with a lower valence cation Sr2+ in the case of La2NiO4 resulted in an increase of Ni3+, consequently the formation of oxygen vacancies, the increase of reducing ability and the increase of catalytic activity. In the oxygen TPD of La2-xSrxNiO4(0 less than or equal to x less than or equal to 1) appeared three peaks, the alpha' peak at about 400K was attributed to the surplus oxygen desorption, the a peak at 700K which approaches to a maxium at x = 0.6 was attributed to the oxygen adsorbed at oxygen vacancies. The beta peak at about 1000K which depends closely on the x and favors the catalytic activity was attributed to the reduction of Ni3+. The catalytic activity of La-2-x SrxNiO4 mixed oxides in the NH3 oxidation in general could be attributed to the extent of the redox reaction: 2Ni(2+) + O-2 + V-0(..) reversible arrow 2Ni(3+) + 20(-) where V-0(..) representes the oxygen vacancies and O- the oxygen species adsorbed at the vacancies.

pCO(2) and carbon fluxes across sea-air interface in the Changjiang Estuary and Hangzhou Bay

Partial pressure of CO2 (pCO(2)) was investigated in the Changjiang (Yangtze River) Estuary, Hangzhou Bay and their adjacent areas during a cruise in August 2004, China. The data show that pCO(2) in surface waters of the studied area was higher than that in the atmosphere with only exception of a patch east of Zhoushan Archipelago. The pCO(2) varied from 168 to 2 264 mu atm, which fell in the low range compared with those of other estuaries in the world. The calculated sea-air CO2 fluxes decreased offshore and varied from -10.0 to 88.1 mmol m(-2) d(-1) in average of 24.4 +/- 16.5 mmol m(-2) d(-1). Although the area studied was estimated only 2 x 10(4) km(2), it emitted (5.9 +/- 4.0) x 10(3) tons of carbon to the atmosphere every day. The estuaries and their plumes must be further studied for better understanding the role of coastal seas playing in the global oceanic carbon cycle.

Capillary zone electrophoresis characterization of low molecular weight heparin binding to interleukin 2

A method based on capillary zone electrophoresis (CZE) was used to study the interaction between low molecular weight heparin (LMWH) and interleukin 2 (IL-2). The results showed that the increase of the concentration of LMWH led to the decrease of the peak height and the increase of the peak width of IL-2, but the peak areas were kept constant. The binding constant of IL-2 with LMWH was calculated as 1.2 x 10(6) M(-1) by Scatchard analysis, which is in good agreement with the results found in the references using enzyme-linked immunosorbent assay (ELISA). The results demonstrated that the interaction between IL-2 and LMWH is of fast on-and-off kinetic binding reaction. CZE might be used to study not only slow on-and-off rates interactions, but also fast on-and-off rates ones. The binding constant can be calculated easily, and the method can be applied to study a wide range of heparin-protein interactions. (c) 2005 Elsevier B.V. All rights reserved.

Detection of amino-terminal extracellular domain of somatostatin receptor 2 by specific monoclonal antibodies and quantification of receptor density in medulloblastoma.

Somatostatin receptor 2 (SSTR2) is expressed by most medulloblastomas (MEDs). We isolated monoclonal antibodies (MAbs) to the 12-mer (33)QTEPYYDLTSNA(44), which resides in the extracellular domain of the SSTR2 amino terminus, screened the peptide-bound MAbs by fluorescence microassay on D341 and D283 MED cells, and demonstrated homogeneous cell-surface binding, indicating that all cells expressed cell surface-detectable epitopes. Five radiolabeled MAbs were tested for immunoreactive fraction (IRF), affinity (KA) (Scatchard analysis vs. D341 MED cells), and internalization by MED cells. One IgG(3) MAb exhibited a 50-100% IRF, but low KA. Four IgG(2a) MAbs had 46-94% IRFs and modest KAs versus intact cells (0.21-1.2 x 10(8) M(-1)). Following binding of radiolabeled MAbs to D341 MED at 4 degrees C, no significant internalization was observed, which is consistent with results obtained in the absence of ligand. However, all MAbs exhibited long-term association with the cells; binding at 37 degrees C after 2 h was 65-66%, and after 24 h, 52-64%. In tests with MAbs C10 and H5, the number of cell surface receptors per cell, estimated by Scatchard and quantitative FACS analyses, was 3.9 x 10(4) for the "glial" phenotype DAOY MED cell line and 0.6-8.8 x 10(5) for four neuronal phenotype MED cell lines. Our results indicate a potential immunotherapeutic application for these MAbs.

Influencia de distintas citocininas en el cultivo in vitro de apices caulinares de Fragaria x ananassa y F. virginiana

p.65-70

Electrochemical oxidation of nitrite and the oxidation and reduction of NO2 in the room temperature ionic liquid [C(2)mim][NTf2]

The electrochemical oxidation of potassium nitrite has been studied in the room temperature ionic liquid (RTIL) [C(2)mim][NTf2] by cyclic voltammetry at platinum electrodes. A chemically irreversible oxidation peak was observed, and a solubility of 7.5(+/- 0.5) mM and diffusion coefficient of 2.0(+/- 0.2) x 10(-11) m(2) s(-1) were calculated from potential step chronoamperometry on the microdisk electrode. A second, and sometimes third, oxidation peak was also observed when the anodic limit was extended, and these were provisionally assigned to the oxidation of nitrogen dioxide (NO2) and nitrate (NO3-), respectively. The electrochemical oxidation of nitrogen dioxide gas (NO2) was also studied by cyclic voltammetry in [C(2)mim][NTf2] on Pt electrodes of various size, giving a solubility of ca. 51(+/- 0.2) mM and diffusion coefficient of 1.6(+/- 0.05) x 10(-10) m(2) s(-1) (at 25 degrees C). It is likely that NO2 exists predominantly as its dimer, N2O4, at room temperature. The oxidation mechanism follows a CE process, which involves the initial dissociation of the dimer to the monomer, followed by a one-electron oxidation. A second, larger oxidation peak was observed at more positive potentials and is thought to be the direct oxidation of N2O4. In addition to understanding the mechanisms of NO2- and NO2 oxidations, this work has implications in the electrochemical detection of nitrite ions and of NO2 gas in RTIL media, the latter which may be of particular use in gas sensing.

An electrochemical study of PCl3 and POCl3 in the room temperature ionic liquid [C(4)mpyrr][N(Tf)(2)]

Voltammetric studies of PCl3 and POCl3 have not been reported in the literature to date, probably due to the instability of these molecules in conventional aprotic solvents giving unstable and irreproducible results. From a previous study [Amigues et al. Chem. Commun. 2005, 1-4], it was found that ionic liquids have the ability to offer a uniquely stable solution phase environment for the study of these phosphorus compounds. Consequently, the electrochemistry of PCl3 and POCl3 has been studied by cyclic voltammetry on a gold microelectrode in the ionic liquid [C(4)mpyrr][N(Tf)(2)] (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide). For both compounds, reduction and oxidation waves were observed and a tentative assignment of the waves is given. For PCl3, the reduction was thought to proceed via the following mechanism: PCl3 + e(-) h reversible arrow PCl3-, PCl3- reversible arrow Cl- + (PCl2)-Cl-center dot, (and) Cl- + PCl3 h PCl4-. For POCl3, the suggested reduction mechanism was analogous to that of PCl3: POCl3 + e(-) reversible arrow POCl3-, POCl3- reversible arrow Cl- + (POCl2)-O-center dot, and Cl- + POCl3 h POCl4-. In both cases (PCl2)-Cl-center dot and (POCl2)-O-center dot are likely to engage in further reactions. Potential step microdisk chronoamperometry was carried out on the reductive waves of PCl3 and POCl3 to measure diffusion coefficients and number of electrons transferred. It was found that the diffusion of PCl3 was unusually slow (3.1 x 10(-12) m(2) s(-1)): approximately 1 order of magnitude less than that for POCl3 (2.2 x 10(-11) m(2) s(-1)). For both PCl3 and POCl3, a

Creation of persistent, straight, 2 mm long laser driven channels in underdense plasmas

The experimental study of the behavior of deuterium plasma with densities between 2 X 1018 and 2 x 10(20) cm(-3), subjected to a 6 TW, 30 ps, 3 X 10(18) W cm(-2) laser pulse, is presented Conclusive experimental proof that a single straight channel is generated when the laser pulse interacts with the lowest densities is provided This channel shows no small-scale longitudinal density modulations, extends up to 2 mm in length and persists for up to 150 ps after the peak of the interaction Bifurcation of the channel after 1 mm propagation distance is observed for the first time For higher density interactions, above the relativistic self-focusing threshold, bubblelike structures are observed to form at late times These observations have implications for both laser wakefield accelerators and fast ignition inertial fusion studies (C) 2010 American Institute of Physics [doi 10 1063/1 3505305]

DNA double-strand break distributions in X-ray and alpha-particle irradiated V79 cells: Evidence for non-random breakage

Many studies have shown that with increasing LET of ionizing radiation the RBE (relative biological effectiveness) for dsb (double strand breaks) induction remains around 1.0 despite the increase in the RBE for cell killing. This has been attributed to an increase in the complexity of lesions, classified as dsb with current techniques, at multiply damaged sites. This study determines the molecular weight distributions of DNA from Chinese hamster V79 cells irradiated with X-rays or 110 keV/mu m alpha-particles. Two running conditions for pulsed-field gel-electrophoresis were chosen to give optimal separation of fragments either in the 225 kbp-5.7 Mbp range or the 0.3 kbp to 225 kbp range. Taking the total fraction of DNA migrating into the gel as a measure of fragmentation, the RBE for dsb induction was less than 1.0 for both molecular weight regions studied. The total yields of dsb were 8.2 x 10(-9) dsb/Gy/bp for X-rays and 7.8 x 10(-9) dsb/Gy/bp for a-particles, measured using a random breakage model. Analysis of the RBE of alpha-particles versus molecular weight gave a different response. In the 0.4 Mbp-57 Mbp region the RBE was less than 1.0; however, below 0.4 Mbp the RBE increased above 1.0. The frequency distributions of fragment sizes were found to differ from those predicted by a model assuming random breakage along the length of the DNA and the differences were greater for alpha-particles than for X-rays. An excess of fragments induced by a single-hit mechanism was found in the 8-300 kbp region and for X-rays and alpha-particles these corresponded to an extra 0.8 x 10(-9) and 3.4 x 10(-9) dsb/bp/Gy, respectively. Thus for every alpha-particle track that induces a dsb there is a 44% probability of inducing a second break within 300 kbp and for electron tracks the probability is 10%. This study shows that the distribution of damage from a high LET alpha-particle track is significantly different from that observed with low LET X-rays. In particular, it suggests that the fragmentation patterns of irradiated DNA may be related to the higher-order chromatin repealing structures found in intact cells.

BUCKLED LAYER STRUCTURE FOR ATOMIC ADSORPTION ON W(100) - THE (ROOT-2X-ROOT-2)R45-DEGREES NITROGEN STRUCTURE FROM ATLEED

Adsorption of 0.5 monolayer of N adatoms on W{100} results in a sharp (root 2 X root 2)R45 degrees LEED pattern. The only previous quantitative LEED study of this system gave a simple overlayer model with a Pendry R-factor of 0.55. An exhaustive search has been made of possible structures, including a novel vacancy reconstruction, displacive reconstructions and underlayer adsorption. From this work a new overlayer structure is derived with an R(p) value of 0.22, displaying a considerable buckling of 0.27 +/- 0.05 Angstrom within the second W layer and consequently involving large changes in the interlayer spacings of the surface. The N adatom is pseudo-five-fold coordinated to the W surface, bonding to a second-layer W atom with a nearest-neighbour bond length of 2.13 Angstrom and with the four next-nearest-neighbour W atoms in the surface plane at 2.27 Angstrom. The structure does not resolve the work function anomaly observed on this surface.