Light Emission in the Unipolar Regime of Ambipolar Organic Field‐Effect Transistors

Light emission from ambipolar organic field‐effect transistors (OFETs) is often observed when they are operated in the unipolar regime. This is unexpected, the light emission should be completely suppressed, because in the unipolar regime only one type of charge carrier is accumulated. Here, an electroluminescent diketopyrrolopyrrole copolymer is investigated. Local potential measurements by scanning Kelvin probe microscopy reveal a recombination position that is unstable in time due to the presence of injection barriers. The electroluminescence and electrical transport have been numerically analyzed. It is shown that the counterintuitive unipolar light emission is quantitatively explained by injection of minority carriers into deep tail states of the semiconductor. The density of the injected minority carriers is small. Hence they are relatively immobile and they recombine close the contact with accumulated majority carriers. The unipolar light output is characterized by a constant efficiency independent of gate bias. It is argued that light emission from OFETs predominantly originates from the unipolar regime when the charge transport is injection limited.     

High Speed and High Resolution Measurements on Submicron Capacitors for FeRAM Application

Ferroelectric capacitors of submicron size for nonvolatile memory applications are entering the structure size of nanotechnology. Therefore the signal level for hysteresis measurements is getting much smaller than the influence of the parasitic capacitance of the measurement setup, e.g. caused by the cantilever of a scanning force microscope (SFM) used for contacting. A novel compensation method significantly increases the signal to noise ratio by active cancellation of the parasitic capacitance of the setup during the measurement.     

Differential susceptibility of primary and established human glioma cells to adenovirus infection: targeting via the epidermal growth factor receptor achieves fiber receptor-independent gene transfer

Adenovirus (Ad) vectors are promising for gene therapy of glioma due to their ability to achieve efficient gene transfer upon intratumoral administration. Yet in this context, Ad mediates widespread gene transfer to both tumor and surrounding parenchyma. Ad entry is dependent upon the expression of fiber receptors, such as coxsackie/adenovirus receptor, and alpha(v) integrins on the target cells for binding and internalization, respectively. We hypothesized that the susceptibility of human gliomas to Ad would likely be heterogeneous due to variable expression of these receptors. It was found that established human glioma cell lines exhibited differential susceptibility to Ad-mediated gene transfer, which correlated directly with the level of radiolabeled Ad binding and with the expression of coxsackie/adenovirus receptor but not with the expression of alpha(v) integrins. To circumvent the lack of fiber receptors and to target Ad gene transfer specifically to tumor cells, we used a bispecific antibody conjugate to ablate Ad binding to fiber receptors and retarget binding to the epidermal growth factor receptor (EGFR), a tumor-associated marker negligibly expressed in normal, mitotically quiescent neural tissues. The results demonstrate that EGFR-targeted Ad gene transfer was EGFR specific and independent of fiber-fiber receptor interactions. Furthermore, EGFR targeting significantly enhanced Ad gene delivery to 7 of 12 established glioma cell lines and to 6 of 8 cultured primary gliomas. Interestingly, EGFR-targeted Ad gene transfer did not correlate with EGFR expression across cell lines, suggesting the importance of other factors. This study establishes that fiber receptor expression limits the utility of Ad vectors for gene transfer to glioma cells and suggests that targeting Ad via EGFR may prove valuable for tumor-specific gene transfer to high-grade gliomas. These findings have key relevance in the context of Ad vector-based approaches for glioma gene therapy.     

有限精度时间自动机的可达性检测

为了缓解状态空间爆炸问题,减小模型检测过程中生成的状态空间,加快模型检测速度,引入有限精度时间自动机(finite precision timed automata,简称FPTA)作为实时系统的形式模型,并提出了一种数据结构SDS(series of delay sequence)符号化表示状态空间中的状态集.FPTA只记录时钟变量的整数值及时钟变化的先后次序,从而减小生成的状态空间.在一定的时间约束下,Alur与Dill提出的时间自动机的可达性检测可简化为FPTA的可达性检测.举例描述了状态空间的生成过程和表示方法.最后,列出部分初步的实验结果,分析了SDS的特点及不足.     

Synthetic speech in practice: acceptance and efficiency

The aim of this study was to determine the degree of acceptance of synthetic speech in a practical application and to clarify some of the factors which are important for its acceptance. Synthetic speech was used in two simulated telephone services. The availability of interrrupt facilities, the speaking rate and service type were varied. The performance (success in writing down the requested data) and some subjective reactions were recorded. Performance was worse with synthetic speech in comparison with normal speech. Neither the interrupt facilities nor the speaking rate had any influence on performance. The interrupt facilities were appreciated, although they were hardly used. Having the possibility of interrupting the synthetic speech caused the subjects to judge the system as more flexible and to rate the experienced tempo as slower. The answers on the questions about acceptance suggested a positive effect of the interrupt variable, but this was not significant. Suggestions concerning the use of synthetic speech are given.     

Evidence of platelet activation in hypertension

To test the hypothesis that platelet activation is present in hypertension, we measured plasma markers beta thromboglobulin and soluble P-selectin in hypertensive patients and normotensive controls. Both markers were raised in the patients (P < 0.05), and in a subgroup of patients, beta thromboglobulin was reduced with successful treatment of hypertension with the ACE inhibitor quinapril. We suggest that reversible platelet activation is present in hypertension. This may be a contributing factor to the link between this risk factor and the development of thrombotic disease such as stroke.     

Sex pheromone biosynthesis in the red-banded leafroller moth,studied by mass-labeling with stable isotopes and analysis with mass spectrometry

A technique for mass-labeling was developed to study sex pheromone biosynthesis in the red-banded leafroller moth,Argyrotaenia velutinana. With this technique, the pheromone components and all fatty acyl groups in the pheromone gland were analyzed for incorporation of label in the same analytic ran with gas chromatography-mass spectrometry, using chemical ionization and selected ion monitoring (GC-SIM-CI-MS). Sex pheromone glands were incubated with fatty acids or triacylglycerols labeled with at least three deuterium atoms or carbon-13 atoms. The results of these incubations support an interpretation in which hexadecanoate is chain shortened to tetradecanoate, which is desaturated to produce (E)- and (Z)-11-tetradecenoate precursors for the sex pheromone components (E)- and (Z)-11-tetradecen-1-yl acetate. Labeled (E)- and (Z)-11-tetradecenoyl groups in synthetic triacylglycerols were not incorporated into the sex pheromone components, perhaps indicating that this lipid class is not a donor of the immediate fatty acyl precursors in sex pheromone biosynthesis.