Nanocluster-containing mesoporous magnetoceramics from hyperbranched organometallic polymer precursors

Pyrolysis of hyperbranched poly[1,1'-ferrocenylene(methyl)silyne] (5) yields mesoporous, conductive, and magnetic ceramics (6). Sintering at high temperatures (1000-1200 degrees C) under nitrogen and argon converts 5 to 6N and 6A, respectively, in similar to 48-62% yields. The ceramization yields of 5 are higher than that (similar to 36%) of its linear counterpart poly[1,1'-ferrocenylene(dimethyl)silylene] (1), revealing that the hyperbranched polymer is superior to the linear one as a ceramic precursor. The ceramic products 6 are characterized by SEM, XPS, EDX, XRD, and SQUID. It is found that the ceramics are electrically conductive and possess a mesoporous architecture constructed of tortuously interconnected nanoclusters. The iron contents of 6 estimated by EDX are 36-43%, much higher than that (11%) of the ceramic 2 prepared from the linear precursor 1. The nanocrystals in 6N are mainly alpha-Fe2O3 whereas those in 6A are mainly Fe3Si. When magnetized by an external field at room temperature, 6A exhibits a high-saturation magnetization (M-s similar to 49 emu/g) and near-zero remanence and coercivity; that is, 6A is an excellent soft ferromagnetic material with an extremely low hysteresis loss.

Effect on the property of the photoinduced carrier transport of CdS as sensitizer for TiO2 nanoparticulate thin films

The TiO2 nanoparticle thin films have been sensitized in situ with CdS nanoparticles. The SPS measurement showed that large surface state density was present on the TiO2 nanoparticles and the surface state can be efficiently decreased by sensitization as well as selecting suitable heat treatment, Both the photocurrent response and the charge recombination kinetics in TiO2 thin films were strongly influenced by trapping/detrapping of surface states. The slow photocurrent response of TiO2 nanoparticulate thin films upon the illumination was attributed to the trap saturation effects, The semiconductor sensitization made the slow photoresponse disappeared and the steady-state photocurrent value increased drastically, which suggested that the sensitization of TiO2 thin films with CdS could get a better charge separation and provide a simple alternative to minimize the effect of surface state on the photocurrent response.

Photosensitization of TiO2 nanoparticulate thin film electrodes by CdS nanoparticles

Surface photovoltage spectra (SPS) measurements of TiO2 show that a large surface state density is present on the TiO2 nanoparticles and these surface states can be efficiently decreased by sensitization using US nanoparticles as well as by suitable heat treatment. The photoelectrochemical behavior of the bare TiO2 thin film indicates that the mechanism of photoelectron transport is controlled by the trapping/detrapping properties of surface states within the thin films, The slow photocurrent response upon the illumination can be explained by the trap saturation effect. For a TiO2 nanoparticulate thin film sensitized using US nanoparticles, the slow photocurrent response disappears and the steady-state photocurrent increases drastically, which suggests that photosensitization can decrease the effect of surface states on photocurrent response.

Luminescent properties of Gd3PO7 : Eu in UV/VUV region

The luminescent properties of Gd3PO7:Eu were investigated in W and VUV regions. This phosphor has such strong emissions around 618.5 nn under UV excitation, especially around 209nn, that it has a better colour saturation than that of Y2O3:Eu. It could be a new potential red phosphor for lamp and other applications with W-excitation source or even for displaying devices. In the VUV excitation spectrum of Eu3+ emissions, energy absorptions by Gd3+, Gd-O and PO43- have been observed, on which it can be inferred that there are three kinds of energy transferring processes to Eu-3(+) ions. The energy absorptions of Gd3+, Gd-O and PO43- are induced by 4f --> 4f transitions, a bandgap transition of Gd3PO7 and intramolecular (2t(2) --> 2a, 3t(2)) transition, respectively. The energy transfer efficiency of the PO43- intramolecular transition is lower compared with that of the bandgap transition (Gd-O).

Binuclear lanthanide complexes as catalysts for the hydrolysis of double-stranded DNA

The efficient cleavage of plasmid DNA ( pCAT) by binuclear lanthanide complexes was investigated. At 37 degrees C and neutral pH, both Ho23+L and Er23+L promoted 100% conversion of supercoiled plasmid to the nicked circular form and linear form in 1 h. The corresponding saturation kinetics curve of cleavage of pCAT plasmid by binuclear lanthanide complexes showed the expected increase with catalyst concentration. (C) 1999 Elsevier Science S.A. All rights reserved.

Monte Carlo simulation of phase separation of A/B/A-B ternary mixtures

Monte Carlo simulations were used to model A/B/A-B ternary mixtures with different AB diblock copolymer volume fractions for which both the dispersed and continuous phase volume fractions were kept constant. For concentrations of the diblock copolymer below a critical value, the domain size increment of the dispersed phase decreases linearly with the copolymer concentration. This is in agreement with the predictions of Noolandi and Hong. The dependence of the domain size as a function of the copolymer volume fraction can also be fitted by the equation of Tang and Huang. Our simulations indicate, for the first time, that the micelles form before saturation of the interface occurs. This means that the formation of the micelles is not a result of the saturation of the interface.

Lanthanide binuclear macrocyclic complexes as synthetic enzymes for the cleavage of DNA

Lanthanide binuclear complexes can accelerate the cleavage of pUC19 plasmid DNA, yielding predominantly linear form. The saturation kinetics of the cleavage of pUC19 was studied. The observed rates with lanthanide binuclear complexes showed the expected increase with the catalyst concentration. The rate of cleavage is greater than that of lanthanide ions alone. (C) 1998 Elsevier Science B.V. All rights reserved.

Studies on synergistic extraction of rare earths(III) with HBTMPTP and primary amine N1923

The synergistic extraction of rare earths(III) with binary systems containing HBTMPTP and primary amine N1923 from sulfuric acid medium was observed, The syner gistic extraction factor(R) decreased with increasing atomic number of lanthanides. Through the methods of slope analysis, constant mole and saturation titration, the synergistic extraction stoichiometry was obtained, The thermodynamic function was calculated, The IR spectra of the saturated synergistic extraction completely confirmed the mechanism.

AN EXPERIMENTAL-STUDY ON MEMBRANE DISTILLATION CRYSTALLIZATION FOR TREATING WASTE-WATER IN TAURINE PRODUCTION

The solution of non-volatile solutes can be concentrated to saturation by membrane distillation. If the solute is easy to crystalize, the membrane distillation-crystallization phenomenon will appear during the membrane distillation of saturated solutions. It is possible that crystalline products are separated from concentrated solutions by a membrane process. In this work the PVDF capillary membrane, which was improved on hydrophobicity by using LiCl instead of a water-soluble polymer as an additive, has been used for treating the waste water of taurine. The crystalline product has been obtained from the waste water by the membrane distillation-crystallization technique. The results have shown good prospects for a membrane distillation application for treatment of industrial waste water.

Effects of Irradiance and Temperature on the Photosynthesis and Vegetative Propagation of Caulerpa serrulata

The photosynthetic oxygen evolution of Caulerpa serrulata was determined with oxygen electrodes. The effects of light and temperature on the growth and regeneration of fragmented C. serrulata thalli were analyzed. The regenerating rate and establishment of different sizes and portions of C. serrulata were studied. The results showed that the light saturation point of C. serrulata was 200 mu mol photons/m(2) per s and the optimum growth temperature was 25-30 degrees C. Under these conditions, the maximum photosynthetic oxygen evolution rate was 15.1 +/- 0.29 mg O-2/mg Chl a/h, the growth rate and elongation rate reached the highest values, 4.67 +/- 0.09 mg FW/d and 0.78 +/- 0.01 mm/d, respectively. The fragmented C. serrulata thalli was regenerated at 20-35 degrees C and survived at 15 degrees C and 200 mu mol photons/m(2) per s. A different survival rate was detected according to fragment size. All of these results indicated that C. serrulata was a candidate to become an invasive species if introduced into a new place. Therefore, we should pay more attention to C. serrulata for its potential threat to marine ecosystem when it is sold for aquarium use.

Study on the GABA gated channels in the neurosecretory cells of MTXO in the eyestalks of Eriocheir sinensis

The responses to rapid application of gamma-aminobutyric acid (GABA) and the GABA receptor characteristics of MTXO neurosecretory cells in the eyestalks of Chinese mitten-handed crab (Eriocheir sinensis) were examined by whole-cell patch clamp. Under current clamp mode, the depolarization and hyperpolarization were evoked from the three types of neurosecretory cells in response to the GABA (0.1 mmol/L) depending on the Nernst Cl- potential. Under voltage clamp mode, the inward Cl- channel currents (I-GABA) were resolved from all three types of neurosecretory cells in response to GABA (0.01similar to5 mmol/L). The GABA currents were activated within 1 200 ms and peaked within 800 ms. No obviously desensitization was observed during GABA application. The dose-response curve showed usual S-shape, with a just-discernible effect at 0.01 mmol/L and near-saturation at 0.5 mmol/L. The GABA currents had reversal potentials that followed Nernst Cl- potentials when [Cl-] was varied. The pharmacological results revealed that the GABA receptor of the crab neurosecretory cells was sensitive to the Cl- channel blockers picrotoxin and niflumic acid (0.5 mmol/L), insensitive to GABA(A) receptor antagonist bicuculline and GABA(C) receptor agonist cis-4-aminocrotonic acid (CACA 1 mmol/L) and trans-4-aminocrotonic (TACA 1 mmol/L).

Effects of cell density, light intensity and mixing on Undaria pinnatifida gametophyte activity in a photobioreactor

An on-line controlled 7 1 sterilizable photobioreactor was used for the optimisation of a culture of gametophytes of Undaria pinnatifida. The gametophytes, which had been stored for three years in a culture cabinet at 16 degreesC, could rapidly grow in the photobioreactor under controlled conditions. The rate of increase of dissolved oxygen and pH were used to monitor the photosynthetic activity. Optimal gametophytes density changed varying the light intensity. The optimal cell densities were 3.24 and 3.45 g FW l(-1) when the cultures were exposed to 61.7 and 82.3 muE m(-2) s(-1), respectively. The optimal cell density was higher under a high photon flux density (PFD) than under low PFD. On the other hand, the optimal light intensities were different for different cell density cultures. The light saturation point was higher at high cell density cultures than at low cell density cultures. The optimal rotational speed was 150 rpm for high cell density culture in the photobioreactor. (C) 2003 Elsevier B.V. All rights reserved.

Relative paleointensity of the geomagnetic field during the past 200 ka from the West Philippine Sea and its chronological significance

Our rock magnetic analysis of core Ph05 from the West Philippine Sea demonstrates that the core preserves a strong, stable remanent magnetization and meets the magnetic mineral criteria for relative paleointensity (RPI) analyses. The magnetic minerals in the sequence are dominated by pseudosingle-domain magnetite, and the concentration of magnetic minerals is at the same scale. Both the conventional normalizing method and the pseudo-Thellier method were used in conjunction with the examination of the rock magnetic properties and natural remanent magnetization. Susceptibility (chi), anhysteretic remnant magnetization (ARM) and saturation isothermal remnant magnetization (SIRM) were used as the natural remanent magnetization normalizer. However, coherence analysis indicated that only ARM is more suitable for paleointensity reconstruction. The age model of core is established based on oxygen isotope data and AMS(14)C data, which is consistent with the age model estimated from RPI records. The relative paleointensity data provide a continuous record of the intensity variation during the last 200 ka, which correlates well with the global references RPI stacks. Several prominent low paleointensity values are identified and are correlated to the main RPI minima in the SINT-200 record, suggesting that the sediments have recorded the real changes of geomagnetic field.

Low-amplitude BSRs and gas hydrate concentration on the northern margin of the South China Sea

The passive northern continental margin of the South China Sea is rich in gas hydrates, as inferred from the occurrence of bottom-simulating reflectors (BSR) and from well logging data at Ocean Drilling Program (ODP) drill sites. Nonetheless, BSRs on new 2D multichannel seismic reflection data from the area around the Dongsha Islands (the Dongsha Rise) are not ubiquitous. They are confined to complex diapiric structures and active fault zones located between the Dongsha Rise and the surrounding depressions, implying that gas hydrate occurrence is likewise limited to these areas. Most of the BSRs have low amplitude and are therefore not clearly recognizable. Acoustic impedance provides information on rock properties and has been used to estimate gas hydrate concentration. Gas hydrate-bearing sediments have acoustic impedance that is higher than that of the surrounding sediments devoid of hydrates. Based on well logging data, the relationship between acoustic impedance and porosity can be obtained by a linear regression, and the degree of gas hydrate saturation can be determined using Archie's equation. By applying these methods to multichannel seismic data and well logging data from the northern South China Sea, the gas hydrate concentration is found to be 3-25% of the pore space at ODP Site 1148 depending on sub-surface depth, and is estimated to be less than values of 5% estimated along seismic profile 0101. Our results suggest that saturation of gas hydrate in the northern South China Sea is higher than that estimated from well resistivity log data in the gas hydrate stability zone, but that free gas is scarce beneath this zone. It is probably the scarcity of free gas that is responsible for the low amplitudes of the BSRs.

海相碳酸盐－稀土元素共沉淀过程中的分异作用研究

本文主要运用稳定加液－反应系统对海水中方解石和文石形成时稀土元素的共沉淀现象进行了分析，研究了稀土元素在固-液体系中的迁移、转化和分配。进而在对其定量描述的前提下，研究了稀土元素共沉淀对各种反应条件的响应，并对共沉淀行为的机制进行了探讨。 本实验首先运用pH测试、高精度滴定分析等手段测定了实验中的一些基本参数，如[H+]、碱度和[Ca2+]，根据计算结果获得了各碳酸体系要素，并以此为基础建立了5℃、15℃和25℃及pCO2=0.003atm下海水中方解石或文石的沉淀动力学方程。实验结果表明： 1）在各条件下，方解石或文石的沉淀速率（R）和其在海水中过饱和度（Ω）存在很好的线性相关性，即海相碳酸盐的沉淀动力学方程可以通过下面的基本表达式来表示：LogR=k*Log(Ω-1)+b ； 2）过高的稀土元素浓度会对文石或方解石的沉淀产生抑制作用，进而对共沉淀过程中YREEs的分异和分馏产生一定的影响。相比方解石而言，文石的沉淀动力学过程承受稀土元素的干扰能力更强； 3）不同温度下得到的方解石或文石各自的沉淀动力学方程存在明显的差异，表明这一过程受热力学因素控制。相对于方解石而言，温度对文石的沉淀动力学的影响更为显著。 与前人研究不同的是，本实验中YREEs的浓度设定在非常低的范围内，从而避免了过高浓度YREEs对方解石或文石沉淀动力学过程的干扰。在最终的反应液中，各种实验条件非常接近自然环境。有关稀土元素的共沉淀行为主要得出以下定性或定量化结论： 1）YREEs在随方解石或文石的共沉淀过程中，均发生了强烈的分异作用。在方解石实验中，稀土元素的分异系数分布曲线呈凸状分布；而在文石实验中，稀土元素的分异系数随原子序数的增加逐渐减小，遵循镧系收缩的规律。总的来说，稀土元素，尤其轻稀土元素在文石中的分异作用要强于方解石。 2）无论是方解石还是文石，沉淀速率对YREEs的分异作用都有着明显的影响。在方解石中，YREEs的分异系数随沉淀速率的增加呈一致性递减趋势；而在文石中，其分异系数对文石沉淀速率有着截然不同的响应：轻稀土元素（La, Ce, Nd, Sm, Eu, Gd）的分异系数随文石沉淀速率的增加而下降，而重稀土元素（Ho, Y, Tm, Yb , Lu）的分异系数则随文石沉淀速率的增加呈上升趋势。 3）在方解石中YREEs的分异系数之间存在非常好的相互关系，表明这些元素是以成比例的方式参与共沉淀。整个谱系呈现中等强度的分馏，MREE相对于LREE和HREE要更为富集；在文石中由于沉淀速率的作用不同，只有Y、Ho、Yb、Lu等元素的分异系数之间有较好的相互关系。YREEs出现了差异性的强烈分馏，在新生成沉淀中轻稀土元素相对于重稀土元素强烈富集。 4）YREEs在溶液中和碳酸盐晶体表面的碳酸根配位形式对YREEs在共沉淀过程中的分异作用极为重要，YREEs在碳酸盐晶体表面的吸附是整个谱系发生分馏效应的关键环节。对于文石来讲，晶体中有效YREE离子和Ca离子半价大小之间的相近程度是其分馏效应的关键因素；而对于方解石来说，YREEs在方解石晶格中的安置就是其分馏效应的关键控制因子，但在晶格安置中起到关键作用的是YREEs和方解石中O原子之间离子键M-O的键长，而非离子半径。 5）综合YREEs在方解石中的分异作用和分馏效应，我们认为M2(CO3)3-CaCO3和MNa(CO3)2-CaCO3是最为可能的两种固体溶液形成模式。 最为重要的是，对比我们的实验结果与前人在灰岩、叠层石、微生物成因碳酸盐等方解石质载体中的研究成果，两者之间出现了非常好的一致性。我们认为方解石质载体将是重建古海水中稀土元素相关信息的重要工具。相比之下，文石质载体不适合作为类似的载体。