Smart universal multiple-valued logic gates by transferring single electrons

This paper proposes smart universal multiple-valued (MV) logic gates by transferring single electrons (SEs). The logic gates are based on MOSFET based SE turnstiles that can accurately transfer SEs with high speed at high temperature. The number of electrons transferred per cycle by the SE turnstile is a quantized function of its gate voltage, and this characteristic is fully exploited to compactly finish MV logic operations. First, we build arbitrary MV literal gates by using pairs of SE turnstiles. Then, we propose universal MV logic-to-value conversion gates and MV analog-digital conversion circuits. We propose a SPICE model to describe the behavior of the MOSFET based SE turnstile. We simulate the performances of the proposed gates. The MV logic gates have small number of transistors and low power dissipations.

Design of novel three port optical gates scheme for the integration of large optical cavity electroabsorption modulators and evanescently-coupled photodiodes

This paper presents a novel scheme to monolithically integrate an evanescently-coupled uni-travelling carrier photodiode with a planar short multimode waveguide structure and a large optical cavity electroabsorption modulator based on a multimode waveguide structure. By simulation, both electroabsorption modulator and photodiode show excellent optical performances. The device can be fabricated with conventional photolithography, reactive ion etching, and chemical wet etching.

Compact universal logic gates realized using quantization of current in nanodevices

This paper proposes novel universal logic gates using the current quantization characteristics of nanodevices. In nanodevices like the electron waveguide (EW) and single-electron (SE) turnstile, the channel current is a staircase quantized function of its control voltage. We use this unique characteristic to compactly realize Boolean functions. First we present the concept of the periodic-threshold threshold logic gate (PTTG), and we build a compact PTTG using EW and SE turnstiles. We show that an arbitrary three-input Boolean function can be realized with a single PTTG, and an arbitrary four-input Boolean function can be realized by using two PTTGs. We then use one PTTG to build a universal programmable two-input logic gate which can be used to realize all two-input Boolean functions. We also build a programmable three-input logic gate by using one PTTG. Compared with linear threshold logic gates, with the PTTG one can build digital circuits more compactly. The proposed PTTGs are promising for future smart nanoscale digital system use.

Demonstration of directed XOR/XNOR logic gates using two cascaded microring resonators

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Monolithic optical gates based on integration of evanescently-coupled uni-traveling-carrier photodiodes and electroabsorption modulators

We report on chip-scale optical gates based on the integration of evanescent waveguide unitraveling-carrier photodiodes (EC-UTC-PDs) and intra-step quantum well electroabsorption modulators (IQW-EAMs) on n-InP substrates. These devices exhibit simultaneously 2.1 GHz and -16.2 dB RF-gain at 21 GHz with a 450 Omega thin-film resistor and a bypass capacitor integrated on a chip.

Potassium-Lead-Switched G-Quadruplexes: A New Class of DNA Logic Gates

A cation-driven allosteric G-quadruplex DNAzyme (PW17) was utilized to devise a conceptually new class of DNA logic gate based on cation-tuned ligand binding and release. K+ favors the binding of hemin to parallel-stranded PW17, thereby promoting the DNAzyme activity, whereas Pb2+ induces PW17 to undergo a parallel-to-antiparallel conformation transition and thus drives hemin to release from the G-quadruplex, deactivating the DNAzyme. Such a K+-Pb2+ switched G-quadruplex, in fact, functions as a two-input INHIBIT logic gate. With the introduction of another input EDTA, this G-quadruplex can be further utilized to construct a reversibly operated IMPLICATION gate.

Quantum computation based on a quantum switch in cavity QED

A feasible scheme for constructing quantum logic gates is proposed on the basis of quantum switches in cavity QED. It is shown that the light field which is fed into the cavity due to the passage of an atom in a certain state can be used to manipulate the conditioned quantum logical gate. In our scheme, the quantum information is encoded in the states of Rydberg atoms and the cavity mode is not used as logical qubits or as a communicating "bus"; thus, the effect of atomic spontaneous emission can be neglected and the strict requirements for the cavity can be relaxed.

植物结构专题研究

1． 裸子植物次生韧皮部中晶体的分布类型及其意义 应用偏光镜检术和扫描电境一一能谱分析等手段对1 1科30种裸子植物次生韧皮部中晶体的形状、大小、分布类型和化学成分进行了系统研究。结果发现，所有的观察种类都具有晶体，钙是晶体的主要成分。在苏铁科、银杏科和松科，晶体存在于韧皮薄壁组织细胞的胞腔中：在其他各科，晶体则主要存在于韧皮细胞的胞壁上;通常胞腔中的晶体通常比胞壁上的大．苏铁科、银杏科和松科的晶体形状分别足棱形晶体、晶簇和柱状晶体或方形晶体．其他各科的晶体形状均为沙晶，但分布的部位各不相同。在杉科、柏科、和罗汉松科的韧皮部中，品体主要嵌埋在各类细胞的径向壁上：在三尖杉科的韧皮部，晶体主要存在于部分薄壁组织细胞的弦向壁上：在红豆杉科（澳洲红豆杉属除外），晶体嵌埋在韧皮纤维的外侧壁上;在麻黄科、买麻藤科，晶体主要存在于薄壁细胞间的胞间隙中，偶尔也在薄壁组织细胞的内侧，但在裸子植物的韧皮部，未见典型的针晶。根据晶体的上述变化，将晶体分布类型分成棱形晶体在薄壁组织细胞腔内、簇晶在溥壁组织细胞腔内、柱形晶体在薄壁组织细胞腔内、沙品在韧皮细胞壁上、沙品在韧皮纤维壁上和沙晶在韧皮薄壁组织细胞间的胞间隙内等六大类型，并依此讨论了它们在裸予植物各类群中的分类意义． 在红豆杉科中，晶体仪存在于厚壁组织细胞类的韧皮纤维上。根据该五属韧皮纤维．L晶体的比较观察，发现红豆杉属、白豆杉属的韧皮纤维具六角形和方形两种晶体，穗花杉属和榧树属仅具方形一种晶体，澳洲红豆杉属不具晶体．从晶体的有无和晶体的类型，讨论了它们在红豆杉科各属间的分类意义． 2． 长苞铁杉的结构及其系统发育的研究 长苞铁杉足我国特有的珍稀濒危植物。自发现以来，其分类位置曾几度变迁．1931年，郑万钧将其归属于铁杉属。1948年，Gaussen ＆van Campo-Duplan认为它是云南油杉和铁杉的杂交种，主张建立铁油杉属(Ts uga -Keteleeria). 1951年，胡先驌认为长苞铁杉与其他铁杉区别明显，提出建立新属- Nothotsuga. 1957年，喻诚鸿根据木材解剖的结果，认为长苞铁杉木质部缺乏正常树脂道，与铁杉属没有本质上的区别，建议将它归人铁杉属．<<中国植物志>>第七卷设长苞铁杉组(Sect. Heopeuce)，与铁杉组(Sect. Tsuga)平行，同归于铁杉属。 本课题对长苞铁杉营养器官的结构做了研究，发现长苞铁杉成熟部位的次生木质部具正常树脂道，创伤树脂道除切向连续分布外还有单个独生的现象，早晚材过渡不明显，射线管胞不发达，交叉场纹孔以杉木型为主，韧皮部中具树脂腔(Resin caviLy)。叶片气孔雨面生，维管束鞘明显，细胞大小均匀，树脂道1个边生。 上述特征都与铁杉属存在明显区别，因而作者支持胡先驌(1951)、Frankis(1989)、Faljon(1990)等关于建立长苞铁杉属的主张。 3． 白皮松的结构及其系统发育的研究 按<<中国植物志>>第七卷的分类系统，白皮松隶属单维管束亚属白皮松组，但其对分类位置曾有不同看法． 本课题通过白皮松营养体结构的研究，发现它在许多方面与单维管束亚属的其他种类有显著差异，白皮松针叶的气孔分布于背腹雨面，气孔间连结细胞的雨侧具石细胞，副卫细胞为近四方形且数目比较恒定，角质层内表面具深波浪状的胞间凸缘：次生木质部的射线管胞内壁具微锯齿状突起，交叉场纹孔松木型，管胞内表面及纹孔部分具明显的瘤层结构;树皮薄，其最外侧仅保留一层周皮，无内皮外皮之分，外侧的韧皮薄壁组织细胞与射线有明显的扩展与弯曲现象，韧皮薄壁组织细胞中的晶体有长柱形和短柱形雨种类型．依据上述结构特征结合前人从染色体、心边材抽提物化学成分析的研究结果，作者支持将白皮松从单维管束亚属中独立出来，成立白皮松亚属的主张。 4． C02浓度升高对植物生长的影响 大气中C02浓度的升高以及所引起的温室效应已成为了人们普遍关注的焦点。预计到21世纪下半叶，C02浓度将增加一倍(Gates，1983).由于C02是植物光合作用的重要原料， 它的变化将直接影响植物的生长和发育，进而引起生物圈乃至整个生态系统的变化。 本项目通过在人工气候室内增加C02浓度，观察大豆与黄麻的生长及其内部结构的影响。结果表明：在短期内，C02浓度升高对两种植物的生长有促进作用，对植物内部结构也有较明显的影响。其中包括种子的发芽率提高，幼苗生长加快，植株明显增高，叶面积增大，叶片加厚（栅栏组织层数增加），根系数量增多，气孔数量减少，茎干增粗、生长轮加宽，韧皮纤维和木纤维增长、大豆结实率增高。但C02浓度升高对两种植物的长期作用仍有待于进一步研究。 本项目还在进行之中。

Compact Reconfigurable Binary-Decision-Diagram Logic Circuit on a GaAs Nanowire Network

We describe a reconfigurable binary-decision-diagram logic circuit based on Shannon's expansion of Boolean logic function and its graphical representation on a semiconductor nanowire network. The circuit is reconfigured by using programmable switches that electrically connect and disconnect a small number of branches. This circuit has a compact structure with a small number of devices compared with the conventional look-up table architecture. A variable Boolean logic circuit was fabricated on an etched GaAs nanowire network having hexagonal topology with Schottky wrap gates and SiN-based programmable switches, and its correct logic operation together with dynamic reconfiguration was demonstrated.

Compact voltage-mode multi-valued literal gate using nanoscale ballistic MOSFETs

A CMOS voltage-mode multi-valued literal gate is presented. The ballistic electron transport characteristic of nanoscale MOSFETs is smartly used to compactly achieve universal radix-4 literal operations. The proposed literal gates have small numbers of transistors and low power dissipations, which makes them promising for future nanoscale multi-valued circuits. The gates are simulated by HSPICE.

Fabrication and characterization of active and sequential circuits utilizing Schottky-wrap-gate-controlled GaAs hexagonal nanowire network structures

For realization of hexagonal BDD-based digital systems, active and sequential circuits including inverters, flip flops and ring oscillators are designed and fabricated on GaAs-based hexagonal nanowire networks controlled by Schottky wrap gates (WPGs), and their operations are characterized. Fabricated inverters show comparatively high transfer gain of more than 10. Clear and correct operation of hexagonal set-reset flip flops (SR-FFs) is obtained at room temperature. Fabricated hexagonal D-type flip flop (D-FF) circuits integrating twelve WPG field effect transistors (FETs) show capturing input signal by triggering although the output swing is small. Oscillatory output is successfully obtained in a fabricated 7-stage hexagonal ring oscillator. Obtained results confirm that a good possibility to realize practical digital systems can be implemented by the present circuit approach.

Resonant tunneling through S- and U-shaped graphene nanoribbons

We theoretically investigate resonant tunneling through S- and U-shaped nanostructured graphene nanoribbons. A rich structure of resonant tunneling peaks is found emanating from different quasi-bound states in the middle region. The tunneling current can be turned on and off by varying the Fermi energy. Tunability of resonant tunneling is realized by changing the width of the left and/or right leads and without the use of any external gates.

Single-electron multiple-valued memory using ultra-small floating gate metal-oxide-semiconductor field effect transistor

This paper proposes a novel single-electron multiple-valued memory. It is a metal-oxide-semiconductor field effect transistor (MOS)-type memory with multiple separate control gates and floating gate layer, which consists of nano-crystal grains. The electron can tunnel among the grains (floating gates) and between the floating gate layer and the MOS channel. The memory can realize operations of 'write', 'store' and 'erase' of multiple-valued signals exceeding three values by controlling the single electron tunneling behavior. We use Monte Carlo method to simulate the operation of single-electron four-valued memory. The simulation results show that it can operate well at room temperature.

Broadband polarization-insensitive semiconductor optical amplifier gate with tensile InGaAs quasi-bulk and compressively strained InGaAs wells

A novel wideband polarization-insensitive semiconductor optical amplifier (SOA) gate containing compressively strained InGaAs quantum wells and tensile-strained InGaAs quasi-bulk layers is developed. The fabricated SOA gates have a wide 3-dB optical bandwidth of 102 nm, less than 0.8-dB polarization sensitivity, more than 50-dB extinction ratio, and less than 75-mA fiber-to-fiber lossless operating current. (C) 2004 Society of Photo-Optical Instrumentation Engineers.