Negative differential resistance and multilevel memory effects in organic devices

Negative differential resistance ( NDR) and multilevel memory effects were obtained in organic devices consisting of an anthracene derivative, 9,10-bis-{ 9,9-di-[ 4-(phenyl-p-tolyl-amino)-phenyl]-9H-fluoren-2-yl}-anthracene ( DAFA), sandwiched between Ag and ITO electrodes. The application of a negative bias voltage leads to negative differential resistance in current-voltage characteristics and different negative voltages produce different conductance currents, resulting in the multilevel memory capability of the devices. The NDR property has been attributed to charge trapping at the DAFA/Ag interface. This opens up a wide range of application possibilities of such organic-based NDR devices in memory and logic circuits.

Electrochemical properties of rare earth AB(3)-type alloy as negative electrode material in MH-Ni battery

Electrochemical properties of rare earth AB(3)-type hydrogen storage alloys as negative electrode material and a polymer instead of 6 M KOH aqueous solution as solid state electrolyte in MH-Ni battery have been investigated at room temperature and 28degreesC first time. The partial replacement of Ni by Al and Mn elements increases the specific capacity and cycle stability of the alloy.

Studies on negative electrospray ionization mass spectrometry on saponins

Two kinds of saponins have been investigated by negative electrospray ionization (NESI) mass spectrometry. Under ESI conditions, the [M - H](-) ions of saponins were observed which provide the molecular weights of saponins. The fragment pathways of [M - H](-) ions of these two saponins depend on their structures. For steroidic saponins, [M - H](-) ion only produces the fragment ions by the losses of sugar units. For oleanolic saponins, [M - H](-) ion yields the cross-ring ions as well as the fragment ions by the losses of sugar units. Moreover, the abundance of the former is higher than that of the latter. The characteristic fragments are used to provide the sequence and some linkage information of sugar moieties of saponins. Especially, their fragment difference strongly depends on the linkage between the aglycone and the sugar moieties.

Positive- and negative-ion matrix-assisted laser desorption/ionization mass spectrometry of saccharides

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) of oligosaccharides and polysaccharides has been investigated in detail, It is demonstrated that cationized species of oligosaccharides, [M+Na](+) and [M+K](+), are dominant products under the MALDI condition, and negative ions of oligosaccharides are not formed to any significant extent in this process, The molecular masses of polysaccharides are similarly determined by positive- and negative-ion MALDI-MS with the help of column chromatography. The distinction between positive- and negative-ion MALDI mass spectra of oligo-and polysaccharides indicates that the MALDI processes for saccharides vary with molecular mass. The matrix plays a more important role in the ionization process for oligosaccharides, while in the desorption process for polysaccharides. (C) 1998 John Wiley & Sons, Ltd.

Color filters with negative birefringence for liquid crystal display use

We have developed a special color film with negative birefringence, which can work as a color filter and a viewing angle extension film for liquid crystal displays (LCDs). A high-performance polyimide (PI), which can be dissolved in the usual organic solvent and shows negative birefringence after lamination, was synthesized to fabricate the film. By mixing PI with suitable proportions of green, blue or red pigment in the solvent, then laminating them onto a glass substrate, we obtained color films with good transmission spectra and suitable chromatic coordinates. The results of our experiments show that the color filters still have negative birefringence but a little lower than that of the pure PI film. and can therefore work as compensation films for normal white twist nematic liquid crystal displays (TN-LCD).

栉孔扇贝免疫致敏（immune priming)现象及其机制的初步研究

栉孔扇贝是我国重要的海水养殖品种，自1997年以来陆续爆发的大规模死亡，不仅造成了巨大的经济损失，而且直接威胁到现有产业的生存和发展。本研究通过比较扇贝在连续刺激条件下的不同免疫反应，推测栉孔扇贝中有无免疫致敏和记忆现象，观察短期免疫刺激对扇贝再次遇到相同病原物刺激时死亡率的影响，探讨栉孔扇贝的免疫致敏作用，并对其机制进行初步探讨，以期更好地了解扇贝的免疫防御机制，为扇贝病害防治提供参考。 利用荧光实时定量PCR技术检测了扇贝受到鳗弧菌连续等量刺激后两种重要病原识别受体（PRR）基因的表达。结果显示，在受到连续两次刺激后CfPGRP-S1、LGBP基因的表达量均有不同程度的增加。其中CfPGRP-S1基因在受到第二次刺激后表达量增加的幅度高于第一次，且基因表达显著性增加的时间比第一次提前；LGBP基因在第二次刺激后，表达量显著性增加的时间也比第一次提前。同时，对同批处理的扇贝进行重要免疫指标的检测分析发现两次刺激后吞噬率变化不显著，而第二次刺激后吞噬指数的最大峰值高于第一次，并且最大峰值出现的时间比第一次提前；血淋巴中的抗菌活力和肝胰腺中SOD、MDA含量在两次刺激前后的变化不显著。在脊椎动物中，识别能力和抗菌能力的提高是免疫记忆的两个重要特点，栉孔扇贝在第二次免疫刺激后PRR识别能力的提高和吞噬作用的增强，说明扇贝中可能存在类似脊椎动物免疫记忆的免疫致敏作用。对扇贝进行两次鳗弧菌浸泡刺激，第一次为短期浸泡刺激，第二次为长期浸泡刺激。结果发现，第一次浸泡过的扇贝在遭受相同病原第二次刺激时，在一定时间段内其死亡率比未受第一次刺激的扇贝极显著降低，表明第一次的短期病原刺激增强了扇贝对第二次刺激的抵抗能力。同时比较第二次刺激过程中扇贝免疫指标的变化发现经过短期刺激扇贝的吞噬作用、ACP和AKP活性比未受过刺激的扇贝显著增强，而其他指标包括POL、SOD则差异不显著，说明增强的吞噬作用、ACP和AKP活性与扇贝的死亡率下降有关。研究结果表明栉孔扇贝中存在免疫致敏（immune priming）现象，短期刺激可以提高扇贝的免疫反应能力，增强扇贝机体对相同病原物的抵抗能力。

Global negative vegetation feedback to climate warming responses of leaf litter decomposition rates in cold biomes

Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warming-induced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.

学习不良少年的污名效应研究

Stigma is defined as a sign of disgrace or discredit that sets a person apart from others. Stigmatized individuals had been significantly influenced by their group-based stigma. Through the methods of laboratory experiment and questionnaire surveys, the current study started with examining the attitudes of middle school students to the students with learning disabilities (LD), systemly explored the characteristics of perceived stigma and self-stigma of LD students, the mechanism that the influences of stigma on students with LD, and the mental control required to cope with the stigma. The results of the present studies had significant implications for the understanding of the LD phenomenon and the intervention of LD adolescents. The results indicate that: 1. Generally, middle school students had negative implicit attitude and negative explicit attitudes towards the LD students. The effect size of the phenomenon of this study is large. The LD students showed a more positive attitude than others on the explicit attitude measure; all students consistently had negative attitudes toward LD students on the implicit attitude indices, in addition, no group differences and gender differences were observed in the implicit attitude. 2. Eight hundred and seventy two students were surveyed to test the reliability and validity of the new developed perceived stigma scale and self-stigma scale. Both questionnaires showed sufficient content validity, construct validity, criterion-related validity and adequate internal consistency reliability. Then, both questionnaires were administered to student with high academic achievement (high achiever), students with middle academic achievement (middle achiever), and LD students. Results revealed that the LD students mildly stigmatized by the social culture. The LD students had more stigma perception and self-stigma than the middle achievers and high achievers. The results also indicated that there were more stigma perception and self-stigma for LD students in grade two than that of LD students in grade one and grade three; meanwhile, male LDstudent hade more stigma perception and self-stigma than female LD students in all grades. 3. A latent variable path analysis was conducted to investigate how the stigma affect the academic goals using the data collected from 186 LD students. The results suggested that the LD-related stigma did not have direct influence on academic goals. The LD-related stigma indirectly influenced the academic goals through mediating effects of self-stigma and academic efficacy. 4. Stereotype threat could have some influences on the relationship between the task feedback and self-esteem. The results of study using eighty-four LD students showed that: when the negative stereotype was not primed, the self-esteem of the LD students was significantly influenced by the feedback of the task: an enhance self-esteem following a positive feedback and a lower self-esteem following a negative feedback. When the negative stereotype was primed, there was no significantly difference between the positive feedback group and negative feedback group. All the results showed that priming the negative stereotype could weaken the influence of feedback to the self-esteem of LD students. 5. There was more cognitive and behavioral control when LD students tried to cope with the stigma by concealing negative academic achievement during an individual interview with an unfamilar expert. The LD students whose academic achievements could be concealed had more thought suppression and thought intrusion and reported more self-monitoring behavior than the participants in the other experimental conditions.