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

Antiferromagnetic materials could represent the future of spintronic applications thanks to the numerous interesting features they combine: they are robust against perturbation due to magnetic fields, produce no stray fields, display ultrafast dynamics and are capable of generating large magneto-transport effects Intense research efforts over the past decade have been invested in unraveling spin transport properties in antiferromagnetic materials Whether spin transport can be used to drive the antiferromagnetic order and how subsequent variations can be detected are some of the thrilling challenges currently being addressed Antiferromagnetic spintronics started out with studies on spin transfer, and has undergone a definite revival in the last few years with the publication of pioneering articles on the use of spin-orbit interactions in antiferromagnets This paradigm shift offers possibilities for radically new concepts for spin manipulation in electronics Central to these endeavors are the need for predictive models, relevant disruptive materials and new experimental designs This paper reviews the most prominent spintronic effects described based on theoretical and experimental analysis of antiferromagnetic materials It also details some of the remaining bottlenecks and suggests possible avenues for future research

Antiferromagnetic spintronics

Materials research has driven the development of modern nano-electronic devices. In particular, research in magnetic thin films has revolutionized the development of spintronic devices1,2 because identifying new magnetic materials is key to better device performance and design. Van der Waals crystals retain their chemical stability and structural integrity down to the monolayer and, being atomically thin, are readily tuned by various kinds of gate modulation3,4. Recent experiments have demonstrated that it is possible to obtain two-dimensional ferromagnetic order in insulating Cr2Ge2Te6 (ref. 5) and CrI3 (ref. 6) at low temperatures. Here we develop a device fabrication technique and isolate monolayers from the layered metallic magnet Fe3GeTe2 to study magnetotransport. We find that the itinerant ferromagnetism persists in Fe3GeTe2 down to the monolayer with an out-of-plane magnetocrystalline anisotropy. The ferromagnetic transition temperature, Tc, is suppressed relative to the bulk Tc of 205 kelvin in pristine Fe3GeTe2 thin flakes. An ionic gate, however, raises Tc to room temperature, much higher than the bulk Tc. The gate-tunable room-temperature ferromagnetism in two-dimensional Fe3GeTe2 opens up opportunities for potential voltage-controlled magnetoelectronics7-11 based on atomically thin van der Waals crystals.

Gate-tunable room-temperature ferromagnetism in two-dimensional Fe 3 GeTe 2 .

Journal of Physics Condensed Matter: Preface

The discovery of materials has often introduced new physical paradigms and enabled the development of novel devices. Two-dimensional magnetism, which is associated with strong intrinsic spin fluctuations, has long been the focus of fundamental questions in condensed matter physics regarding our understanding and control of new phases. Here we discuss magnetic van der Waals materials: two-dimensional atomic crystals that contain magnetic elements and thus exhibit intrinsic magnetic properties. These cleavable materials provide the ideal platform for exploring magnetism in the two-dimensional limit, where new physical phenomena are expected, and represent a substantial shift in our ability to control and investigate nanoscale phases. We present the theoretical background and motivation for investigating this class of crystals, describe the material landscape and the current experimental status of measurement techniques as well as devices, and discuss promising future directions for the study of magnetic van der Waals materials.

Magnetism in two-dimensional van der Waals materials.

Metallic magnetic calorimeters, where deposited energy is detected by measuring a temperature-dependent magnetization with a low-noise SQUID, remain a promising potential route to X-ray spectrometers with energy resolution approaching 1 eV. In this paper we describe our recent work toward array-compatible, high-resolution MMCs fabricated entirely using thin-film techniques. We describe a meander-style pickup loop designed for good coupling to high-efficiency, low noise SQUIDs, as well as considering various routes to a thin-film paramagnetic sensor. We also briefly overview the most promising technology for multiplexing arrays of non-dissipative metallic magnetic calorimeters.

Design, Fabrication, and Multiplexing of Magnetic Calorimeter X-ray Detectors with High-Efficiency SQUID Readout

Field-dependent nonelectronic contributions to thermal conductivity in a metallic ferromagnet with low Gilbert damping

Time-division SQUID multiplexers are used in many applications that require exquisite control of systematic error. One potential source of systematic error is the pickup of external magnetic fields in the multiplexer. We present measurements of the field sensitivity figure of merit, effective area, for both the first stage and second stage SQUID amplifiers in three NIST SQUID multiplexer designs. These designs include a new variety with improved gradiometry that significantly reduces the effective area of both the first and second stage SQUID amplifiers.

Time-division SQUID multiplexers with reduced sensitivity to external magnetic fields

World record energy resolution (DeltaE ~ 25 eV) has recently been demonstrated for soft gamma-ray detectors using small radiation absorbing elements coupled to transition-edge sensors (microcalorimeters). Initial results were obtained with a 1 mm wide by 250 mum thick tin absorber. We are proceeding with construction of arrays of sensors and exploring other absorber materials. Monte Carlo tools, e.g. - GEANT4, are useful for exploring the design space and performance expectations for these arrays of microcalorimeters. In this work, we use simulations to quantify some important characteristics of this emerging technology in the hard X- and gamma-ray regime, such as the effective area and effect of absorber material and thickness. We also explore, through simulations, how these detectors might be used in some interesting applications, like passive assay of spent nuclear fuel from X-ray fluorescence.

Monte Carlo Studies of High Resolution Microcalorimeter Detectors

Spin-tunneling and tunnel magnetoresistance (TMR) attract much attention at the moment because of their promise for magnetic sensors and memory devices. The TMR is analyzed for ferromagnet-insulatorferromagnet junctions, including half-metallic systems. Direct tunneling is shown to be mainly responsible for the observed behavior of conventional junctions, and it is compared with impurity-assisted and resonant spin tunneling. Impurity-assisted tunneling decreases the TMR down to a few percent with conventional electrodes, and spin-flip scattering from defect states will further reduce this value. The same is generally true of a resonant diode type of structure. The model applies to half-metallic systems with 100% spin polarization, where the change of resistance in the absence of spin-flips may be arbitrarily large. Even in the case of imperfect magnetic configurations the resistance change can be a few lo00 percent, as illustrated by CQ-based systems with matching oxides.' Relevance of these results for magnetic oxides with colossal MR will be discussed.

http://ieeexplore.ieee.org/iel4/5941/15837/00737213.pdf

Barry L. Zink

Papers

Design, Fabrication, and Multiplexing of Magnetic Calorimeter X-ray Detectors with High-Efficiency SQUID Readout

Field-dependent nonelectronic contributions to thermal conductivity in a metallic ferromagnet with low Gilbert damping

Time-division SQUID multiplexers with reduced sensitivity to external magnetic fields

Monte Carlo Studies of High Resolution Microcalorimeter Detectors

Tunneling And IR Spectroscopy On Giant Magnetoresistive Amorphous Rare Earth-silicon Alloys