抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Many materials systems are currently under consideration as potential replacements for SiO2 as the gate dielectric material for sub-0.1 μm complementary metal–oxide–semiconductor (CMOS) technology. A systematic consideration of the required properties of gate dielectrics indicates that the key guidelines for selecting an alternative gate dielectric are (a) permittivity, band gap, and band alignment to silicon, (b) thermodynamic stability, (c) film morphology, (d) interface quality, (e) compatibility with the current or expected materials to be used in processing for CMOS devices, (f) process compatibility, and (g) reliability. Many dielectrics appear favorable in some of these areas, but very few materials are promising with respect to all of these guidelines. A review of current work and literature in the area of alternate gate dielectrics is given. Based on reported results and fundamental considerations, the pseudobinary materials systems offer large flexibility and show the most promise toward success...

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High-κ gate dielectrics: Current status and materials properties considerations

There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

Coinage metals, such as Au, Ag, and Cu, have been important materials throughout history.1 While in ancient cultures they were admired primarily for their ability to reflect light, their applications have become far more sophisticated with our increased understanding and control of the atomic world. Today, these metals are widely used in electronics, catalysis, and as structural materials, but when they are fashioned into structures with nanometer-sized dimensions, they also become enablers for a completely different set of applications that involve light. These new applications go far beyond merely reflecting light, and have renewed our interest in maneuvering the interactions between metals and light in a field known as plasmonics.2–6

In plasmonics, the metal nanostructures can serve as antennas to convert light into localized electric fields (E-fields) or as waveguides to route light to desired locations with nanometer precision. These applications are made possible through a strong interaction between incident light and free electrons in the nanostructures. With a tight control over the nanostructures in terms of size and shape, light can be effectively manipulated and controlled with unprecedented accuracy.3,7 While many new technologies stand to be realized from plasmonics, with notable examples including superlenses,8 invisible cloaks,9 and quantum computing,10,11 conventional technologies like microprocessors and photovoltaic devices could also be made significantly faster and more efficient with the integration of plasmonic nanostructures.12–15 Of the metals, Ag has probably played the most important role in the development of plasmonics, and its unique properties make it well-suited for most of the next-generation plasmonic technologies.16–18

1.1. What is Plasmonics?
Plasmonics is related to the localization, guiding, and manipulation of electromagnetic waves beyond the diffraction limit and down to the nanometer length scale.4,6 The key component of plasmonics is a metal, because it supports surface plasmon polariton modes (indicated as surface plasmons or SPs throughout this review), which are electromagnetic waves coupled to the collective oscillations of free electrons in the metal.

While there are a rich variety of plasmonic metal nanostructures, they can be differentiated based on the plasmonic modes they support: localized surface plasmons (LSPs) or propagating surface plasmons (PSPs).5,19 In LSPs, the time-varying electric field associated with the light (Eo) exerts a force on the gas of negatively charged electrons in the conduction band of the metal and drives them to oscillate collectively. At a certain excitation frequency (w), this oscillation will be in resonance with the incident light, resulting in a strong oscillation of the surface electrons, commonly known as a localized surface plasmon resonance (LSPR) mode.20 This phenomenon is illustrated in Figure 1A. Structures that support LSPRs experience a uniform Eo when excited by light as their dimensions are much smaller than the wavelength of the light.



Figure 1

Schematic illustration of the two types of plasmonic nanostructures discussed in this article as excited by the electric field (Eo) of incident light with wavevector (k). In (A) the nanostructure is smaller than the wavelength of light and the free electrons ...



In contrast, PSPs are supported by structures that have at least one dimension that approaches the excitation wavelength, as shown in Figure 1B.4 In this case, the Eo is not uniform across the structure and other effects must be considered. In such a structure, like a nanowire for example, SPs propagate back and forth between the ends of the structure. This can be described as a Fabry-Perot resonator with resonance condition l=nλsp, where l is the length of the nanowire, n is an integer, and λsp is the wavelength of the PSP mode.21,22 Reflection from the ends of the structure must also be considered, which can change the phase and resonant length. Propagation lengths can be in the tens of micrometers (for nanowires) and the PSP waves can be manipulated by controlling the geometrical parameters of the structure.23

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Controlling the synthesis and assembly of silver nanostructures for plasmonic applications

The discovery of the enhancement of Raman scattering by molecules adsorbed on nanostructured metal surfaces is a landmark in the history of spectroscopic and analytical techniques. Significant experimental and theoretical effort has been directed toward understanding the surface-enhanced Raman scattering (SERS) effect and demonstrating its potential in various types of ultrasensitive sensing applications in a wide variety of fields. In the 45 years since its discovery, SERS has blossomed into a rich area of research and technology, but additional efforts are still needed before it can be routinely used analytically and in commercial products. In this Review, prominent authors from around the world joined together to summarize the state of the art in understanding and using SERS and to predict what can be expected in the near future in terms of research, applications, and technological development. This Review is dedicated to SERS pioneer and our coauthor, the late Prof. Richard Van Duyne, whom we lost during the preparation of this article.

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Present and Future of Surface-Enhanced Raman Scattering

Dual floating gate flash memory has been fabricated and characterized to show dynamic operation, non-volatile operation, and simultaneous dynamic and non-volatile operation. The gate stack consists of a thin dielectric separating two floating gates sandwiched between a tunnel dielectric and interpoly dielectric. The quality of the thin dielectric that separates the floating gates is of utmost importance to retain dynamic operation. In this letter, we investigate a dual floating gate memory transistor and show its potential to combine DRAM and flash functionality in the same device.

Dual Floating Gate Unified Memory MOSFET With Simultaneous Dynamic and Non-Volatile Operation

Integrated circuit electrodes include an alloy of a first metal and a second metal having lower work function than the first metal. The second metal also may have higher oxygen affinity than the first metal. The first metal may be Ru, Ir, Os, Re and alloys thereof, and the second metal may be Ta, Nb, Al, Hf, Zr, La and alloys thereof. Both NMOS and the PMOS devices can include gate electrodes of an alloy of the first metal and the second metal having lower work function than the first metal. The PMOS gate electrode may have a higher percentage of the first metal relative to the second metal than the NMOS gate electrode. Thus, a common material system may be used for gate electrodes for both NMOS and PMOS devices.

High/low work function metal alloys for integrated circuit electrodes

The effective work function of PMOS metal gate electrode as a function of intentionally altered HfO2 surfaces was investigated The impact of capping layers, diffusion barriers and interfacial layers on the final work function was also examined The factors responsible for the change in the effective work function after subsequent thermal treatments were identified and routes to maintain the high effective work function have been demonstrated

Dependence of pmos metal work functions on surface conditions of high-k gate dielectrics

Metal gate electrodes consisting of three layered stacks of metals are investigated for complementary metal-oxide-semiconductor device applications. It was observed that the effective work function of the entire gate electrode stack was dominated by the work function of the first metal layer (50A of tantalum nitride) contacting the gate dielectric. No significant difference in the effective oxide thickness was observed in devices with and without the initial tantalum nitride layer. The potential reasons for this, based on the penetration of an electron wave function from the gate electrode to the gate dielectric and gate depletion due to longer Debye length of electrons in tantalum nitride, will be discussed.

Investigation of work function tuning using multiple layer metal gate electrodes stacks for complementary metal-oxide-semiconductor applications

The lanthanum silicate interface engineering has been shown to dramatically improve the mobility of 4H-silicon carbide (SiC) MOSFETs. We studied the impact of post deposition annealing (PDA) conditions and the initial lanthanum oxide (La2O3) thickness on the MOSFET performance. The combination of 900 °C PDA and 1 nm La2O3 leads to highest field-effect mobility. Higher PDA temperature leads to mobility reduction due to lower lanthanum concentration at the SiC/dielectric interface. The peak mobility and threshold voltage show strong dependence on the initial La2O3 thickness.

Veena Misra

Papers

Dual Floating Gate Unified Memory MOSFET With Simultaneous Dynamic and Non-Volatile Operation

High/low work function metal alloys for integrated circuit electrodes

Dependence of pmos metal work functions on surface conditions of high-k gate dielectrics

Investigation of work function tuning using multiple layer metal gate electrodes stacks for complementary metal-oxide-semiconductor applications

Investigation of Lanthanum Silicate Conditions on 4H-SiC MOSFET Characteristics