245 GHz接收机芯片片外测试与实验

为了实现太赫兹气体频谱分析传感器,对245 GHz次谐波接收机芯片的片外测试展开研究。建立了245 GHz次谐波接收机片外测试系统以及基于245 GHz接收机芯片及发射机芯片的气体频谱分析传感器片外展示测试系统,对245 GHz次谐波接收机芯片转换增益和带宽进行测试。片外测试系统得到15 dB转换增益和15 GHz带宽;片外展示测试系统得到9 dB转换增益和16 GHz带宽。片外测试系统和片外展示测试系统结果基本吻合。在片外展示测试系统中加入气腔,即构成气体频谱分析传感器。与现有同类型传感器相比,本文的次谐波接收机具有高增益、高带宽、集成本地振荡信号、低功耗等优势,非常适用于消费电子领域小体积的智能气体频谱分析传感器。     

Polylactide‐block‐Polypeptide‐block‐Polylactide Copolymer Nanoparticles with Tunable Cleavage and Controlled Drug Release

A versatile nanoparticle system is presented in which drug release is triggered by enzymatic polymer cleavage, resulting in a physicochemical change of the carrier. The polylactide‐block‐peptide‐block‐polylactide triblock copolymer is generated by initiation of the ring‐opening polymerization of L‐lactide with a complex bifunctional peptide having an enzymatic recognition and cleavage site (Pro‐Leu‐Gly‐Leu‐Ala‐Gly). This triblock copolymer is specifically bisected by matrix metalloproteinase‐2 (MMP‐2), an enzyme overexpressed in tumor tissues. Triblock copolymer nanoparticles formed by nonaqueous emulsion polymerization are readily transferred into aqueous media without aggregation, even in the presence of blood serum. Cleavage of the triblock copolymer leads to a significant decrease of the glass transition temperature (T_g) from 39 °C to 31 °C, likely mediating cargo release under physiological conditions. Selective drug targeting is demonstrated by hampered mitosis and increased cell death resulting from drug release via MMP‐2 specific cleavage of triblock copolymer carrier. On the contrary, nanocarriers having a scrambled (non‐recognizable) peptide sequence do not cause enhanced cytotoxicity, demonstrating the enzyme‐specific cleavage and subsequent drug release. The unique physicochemical properties, cleavage‐dependent cargo release, and tunability of carrier bioactivity by simple peptide exchange highlight the potential of this polymer‐nanoparticle concept as platform for custom‐designed carrier systems.     

Ortho‐ vs Bay‐Functionalization: A Comparative Study on Tetracyano‐Terrylenediimides

In this paper n‐type semiconductors synthesized via selective fourfold cyanation of the ortho‐ and bay‐positions (2,5,10,13‐ and 1,6,9,14‐positions respectively) of teyrrylenediimides are reported. A detailed study about the impact of the diverse functionalization topologies on the optoelectronic properties, self‐organization from solution, solid‐state packing, and charge carrier transport in field‐effect transistors is presented. The ortho‐substitution preserves the planarity of the core and favors high order in solution processed films. However, the strong intermolecular interactions lead to a microstructure with large aggregates and pronounced grain boundaries which lower the charge carrier transport in transistors. In contrast, the well‐soluble bay‐functionalized terrylenediimide forms only disordered films which surprisingly result in n‐type average mobilities of 0.17 cm²/Vs after drop‐casting with similar values in air. Processing by solvent vapor diffusion enhances the transport to 0.65 cm²/Vs by slight improvement of the order and surface arrangement of the molecules. This mobility is comparable to highest n‐type conductivities measured for solution processed PDI derivatives demonstrating the high potential of TDI‐based semiconductors.     

A 90-nm logic technology featuring strained-silicon

A leading-edge 90-nm technology with 1.2-nm physical gate oxide, 45-nm gate length, strained silicon, NiSi, seven layers of Cu interconnects, and low-/spl kappa/ CDO for high-performance dense logic is presented. Strained silicon is used to increase saturated n-type and p-type metal-oxide-semiconductor field-effect transistors (MOSFETs) drive currents by 10% and 25%, respectively. Using selective epitaxial Si/sub 1-x/Ge/sub x/ in the source and drain regions, longitudinal uniaxial compressive stress is introduced into the p-type MOSEFT to increase hole mobility by >50%. A tensile silicon nitride-capping layer is used to introduce tensile strain into the n-type MOSFET and enhance electron mobility by 20%. Unlike all past strained-Si work, the hole mobility enhancement in this paper is present at large vertical electric fields in nanoscale transistors making this strain technique useful for advanced logic technologies. Furthermore, using piezoresistance coefficients it is shown that significantly less strain (/spl sim/5 /spl times/) is needed for a given PMOS mobility enhancement when applied via longitudinal uniaxial compression versus in-plane biaxial tension using the conventional Si/sub 1-x/Ge/sub x/ substrate approach.     

Elevated temperature performance of pseudomorphic AlGaAs/InGaAsMODFETs

Parametric DC measurements on pseudomorphic AlGaAs/InGaAs modulation-doped field-effect transistors (MODFETs) were carried out over the 300-405 K temperature range. A gradual channel device model was developed to simulate the temperature dependent behavior and assist in the interpretation of the characteristics. The simulations are shown to provide good predictive ability and confirm the physical reasons why the zero temperature coefficient point of a MODFET occurs only for gate bias voltages below the threshold voltage     

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A 200 MHz CMOS Q-enhanced LC bandpass filter

This paper presents design techniques and performance bounds for implementing Q-enhanced, LC bandpass filters in silicon IC technologies. These filters offer significant advantages over switched capacitor and Gm-C based designs, including higher frequency of operation and lower power consumption for a given dynamic range. A prototype 200 MHz, fourth-order filter implemented in a 2 μm n-well CMOS process is described, and measured performance is compared with theoretical predictions. The prototype filter operates at a selectivity Q of 100 and draws less than 8 mA when operating from 3 to 5 V supplies, making it potentially suitable for use as a first IF filter in modern cellular and PCS receivers     

Fluoroscopy-based 3-D reconstruction of femoral bone cement: a new approach for revision total hip replacement

In revision total hip replacement the removal of the distal femoral bone cement can be a time consuming and risky operation due to the difficulty in determining the three-dimensional (3-D) boundary of the cement. We present a new approach to reconstruct the bone cement volume by using just a small number of calibrated multiplanar X-ray images. The modular system design allows the surgeon to react intraoperatively to problems arising during the individual situation. When encountering problems during conventional cement removal, the system can be used on demand to acquire a few calibrated X-ray images. After a semi-automatic segmentation and 3-D reconstruction of the cement with a deformable model, the system guides the surgeon through a free-hand navigated or robot-assisted cement removal. The experimental evaluation using plastic test implants cemented into anatomic specimen of human femoral bone has shown the potential of this method with a maximal error of 1.2 mm (0.5 mm RMS) for the distal cement based on just 4-5 multiplanar X-ray images. A first test of the complete system, comparing the 3-D-reconstruction with a computed tompgraphy data set, confirmed these results with a mean error about 1 mm.     

Gravimetric determination of tannins and their correlations with chemical and protein precipitation methods

Abstract. A method for gravimetric determination of tannins based on binding with insoluble polyvinylpyrrolidone (PVP) is presented. The gravimetric method gives the absolute amount of tannins and avoids problems of standards associated with spectrophotometric methods. The method was applied to nine browse and tree leaves. The values obtained correlate significantly with tannins determined spectrophotometrically, protein precipitation capacities and protein precipitable phenotics. This method together with other tannin assays will be useful in nutritional studies. The present study also demonstrates the different behaviour of tannic acids from different commercial sources towards PVP suggesting the presence of different moieties in tannic acids from different commercial sources and even among batches from the same source thereby affecting the results obtained using the spectrophotometric methods. Use of well-defined tannic acid as a standard in spectrophotometric methods is suggested which will allow meaningful comparison of values obtained from different laboratories.