High retention of polarization in polycrystalline M/PZT/M capacitors in the presence of depolarization field near grain boundaries

Recently, we reported on the photovoltaic current observed in poled capacitors with polycrystalline Pb(ZrTi)O(3) (PZT) films, where (111)-oriented PZT grains are separated by an ultrathin semiconductor PbO phase. This photocurrent is driven by the depolarization field, which is generated by residual uncompensated polarization charge located on grain boundaries near electrodes. We showed that the photocurrent can serve as a criterion of existence of the depolarization field and demonstrated that this field is retained in the film for at least one year. Here, we present new experimental and numerical results which confirm the proposed conception of the photovoltaic effect. We study the photocurrent depending on the kind of electrodes, preliminary illumination in an open-circuit regime, and light intensity of LED, and give evidence of retention of the depolarization field in the films for at least for one and one-half years. The numerical study of the photovoltaic effect at extremely high photogeneration rate shows that total compensation of the polarization charge by photoexcited carriers in these structures is impossible. This photovoltaic effect can be used for nondestructive readout in ferroelectric memory.     

The raison d'être of constitutively active protein kinases: the lesson of CK2

Protein kinases generally are tightly controlled signaling molecules that are switched on only in response to specific stimuli. Exceptionally few protein kinases are constitutively active, the most striking example being provided by CK2 (formerly "casein kinase 2"). Owing to unique structural features, the catalytic activity of CK2 is constantly on, although its targeting can be deeply influenced by the association of its two catalytic subunits (alpha and/or alpha') with a dimeric non catalytic beta subunit. Constitutive activity of CK2 reflects its extraordinary pleiotropy documented by its growing list of >300 protein substrates and is consistent with emerging evidence that CK2 plays an essential role in the cell by counteracting premature and/or unscheduled apoptosis, thus ensuring cell survival under stress conditions.     

Photonic page buffer based on GaAs multiple-quantum-well modulators bonded directly over active silicon complementary-metal-oxide-semiconductor (CMOS) circuits

We present a 2-kbit, 50-Mpage/s, photonic first-in, first-out page buffer based on gallium arsenide/aluminium-gallium arsenide multiple-quantum-well diodes that are flip-chip bonded to submicrometer silicon complementary-metal-oxide-semiconductor circuits. This photonic chip provides nonvolatile storage (buffering), asynchronous-to-synchronous conversion, bandwidth smoothing, tolerance to jitter or skew, spatial format conversion, wavelength conversion, and independent flow control for the input and the output channels. It serves as an interface chip for parallel-accessed optical bit-plane data. It represents the first smart-pixel array that accomplishes the vertical integration of multiple-quantum-well modulators and detectors directly over active silicon VLSI circuits and provides over 340 transistors per optical input-output. Results from high-speed single-channel testing and real-time array operation of the photonic page buffer are reported.     

我在哪 它知道 想去哪 我做主

向北望 在何方? 春节去南方小城游玩，古老街道，沿着崎岖的路悠然信步，好不自在。可每每问路时，总是尴尬无比。“请问，这镇子上哪里有比较有特色的饭馆？”“哦，你从前面路口向西，走过两条巷子再朝北走，会看到一个帆布招牌，那是我们镇上最有名的小吃店了。”     

重质油在CoMo／碳载体催化剂上的加氢处理

本研究以阿拉伯３４５℃＋常压重油为原料油，对几种ＣｏＭｏ／活性炭催化剂进行了约１７天的加氢工业实验研究，着重考察了所用催化剂的活性，并将实验结果与传统的ＣｏＭｏ／Ａｌ２Ｏ３催化剂的实验研究结果作了比较。主要研究结果如下：ＣｏＭｏ／活性炭催化剂的脱金属活性与所选择的活性炭的物性及Ｃｏ、Ｍｏ金属在活性炭上的担载方式有关；在压力１０ＭＰａ下采用ＣｏＭｏ／Ｄａｒｅｏ活性炭催化剂和ＣｏＭｏ／Ａｌ２Ｏ３催化剂     

在原子阱内外玻色凝聚物都相干

最近WolfgangKetterle及其同事在麻省理工学院演示了“原子激光器”，对这件事的报导使物理界人士为之兴奋，自然也吸引了大众媒体的关注。激光的基本特征之一是其相干性，该组提供的证据是惊人的：两团玻色一爱因斯坦凝聚物在从同一陷欧中的捕获态释放出后发生膨胀和重叠，形成高锐度干涉条纹。这种条纹使人联想到双缝相干光波的干涉（见图1）。恐怕不会有人对上述玻色一爱因斯坦凝聚物相干性的证明感到意外。说到底，它是处于量子力学基态的一群原子，可用单一的宏观波函数来描写。但若无实验验证，某些理论研究者会提出以下疑问：谁能确…     

Preparation, characterization, and topical delivery of paromomycin ion pairing

Topical chemotherapy with paromomycin (PA) has been used as an alternative for the treatment of cutaneous leishmaniasis; however, poor skin penetration of this drug limits the efficacy of formulations. The objective of this work was to study the ability of the PA free base to form ion pairing with organic acids, as well as evaluate the effect of these compounds on the topical delivery of PA. PA permeation across intact skin was low, while drug penetration into skin from PA ion pairing was the higher than that observed for the PA base. Data obtained on the stripped skin, a damaged skin model, clearly showed that the ion pairing presented a potential to improve PA skin permeation.