다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

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

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

http://files.janapv.webnode.cz/200000097-8a03f8afdf/ex_bias_nano.pdf

Exchange bias in nanostructures

Metformin is a widely-used drug that results in clear benefits in relation to glucose metabolism and diabetes-related complications. The mechanisms underlying these benefits are complex and still not fully understood. Physiologically, metformin has been shown to reduce hepatic glucose production, yet not all of its effects can be explained by this mechanism and there is increasing evidence of a key role for the gut. At the molecular level the findings vary depending on the doses of metformin used and duration of treatment, with clear differences between acute and chronic administration. Metformin has been shown to act via both AMP-activated protein kinase (AMPK)-dependent and AMPK-independent mechanisms; by inhibition of mitochondrial respiration but also perhaps by inhibition of mitochondrial glycerophosphate dehydrogenase, and a mechanism involving the lysosome. In the last 10 years, we have moved from a simple picture, that metformin improves glycaemia by acting on the liver via AMPK activation, to a much more complex picture reflecting its multiple modes of action. More work is required to truly understand how this drug works in its target population: individuals with type 2 diabetes.

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The mechanisms of action of metformin

The magnetic properties of hematite $(\ensuremath{\alpha}\ensuremath{-}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3})$ particles with sizes of about 16 nm have been studied by use of M\"ossbauer spectroscopy, magnetization measurements, and neutron diffraction. The nanoparticles are weakly ferromagnetic at temperatures at least down to 5 K with a spontaneous magnetization that is only slightly higher than that of weakly ferromagnetic bulk hematite. At $T\ensuremath{\gtrsim}100\mathrm{K}$ the M\"ossbauer spectra contain a doublet, which is asymmetric due to magnetic relaxation in the presence of an electric field gradient in accordance with the Blume-Tjon model. Simultaneous fitting of series of M\"ossbauer spectra obtained at temperatures from 5 K to well above the superparamagnetic blocking temperature allowed the estimation of the pre-exponential factor in N\'eel's expression for the superparamagnetic relaxation time, ${\ensuremath{\tau}}_{0}=(6\ifmmode\pm\else\textpm\fi{}4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\mathrm{s}$ and the magnetic anisotropy energy barrier, ${E}_{\mathrm{bm}}{/k=590}_{\ensuremath{-}120}^{+150}\mathrm{K}.$ A lower value of the pre-exponential factor, ${\ensuremath{\tau}}_{0}{=1.8}_{\ensuremath{-}1.3}^{+3.2}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}\mathrm{s},$ and a significantly lower anisotropy energy barrier ${E}_{\mathrm{bm}}^{\mathrm{magn}}/k=305\ifmmode\pm\else\textpm\fi{}20\mathrm{K}$ was derived from simultaneous fitting to ac and dc magnetization curves. The difference in the observed energy barriers can be explained by the presence of two different modes of superparamagnetic relaxation which are characteristic of the weakly ferromagnetic phase. One mode involves a rotation of the sublattice magnetization directions in the basal (111) plane, which gives rise to superparamagnetic behavior in both M\"ossbauer spectroscopy and magnetization measurements. The other mode involves a fluctuation of the net magnetization direction out of the basal plane, which mainly affects the magnetization measurements.

/pdf/magnetic-properties-of-hematite-nanoparticles-1bktxq4ycx.pdf

Magnetic properties of hematite nanoparticles

The dynamics of a magnetic particle system consisting of ultrafine Fe-C particles of monodisperse nature has been investigated in a large time window, ${10}^{\ensuremath{-}9}--{10}^{4}\mathrm{s}$, using M\"ossbauer spectroscopy, ac susceptibility, and zero field cooled magnetic relaxation measurements. By studying two samples from the same dilution series, with concentrations of 5 and $6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\mathrm{vol}%$, respectively, it has been found that dipole-dipole interaction increases the characteristic relaxation time of the particle system at all temperatures investigated. The results for the most concentrated particle assembly are indicative of collective magnetic dynamics and critical slowing down at a finite temperature, ${T}_{g}\ensuremath{\approx}40\mathrm{K}$. Close to and below the transition temperature, an aging phenomenon is observed, another manifestation of collective magnetic dynamics.

/pdf/dynamics-of-an-interacting-particle-system-evidence-of-gduwer8k4c.pdf

Dynamics of an Interacting Particle System: Evidence of Critical Slowing Down

We present a short overview of the influence of inter-particle interactions on the properties of magnetic nanoparticles. Strong magnetic dipole interactions between ferromagnetic or ferrimagnetic particles, that would be superparamagnetic if isolated, can result in a collective state of nanoparticles. This collective state has many similarities to spin-glasses. In samples of aggregated magnetic nanoparticles, exchange interactions are often important and this can also lead to a strong suppression of superparamagnetic relaxation. The temperature dependence of the order parameter in samples of strongly interacting hematite nanoparticles or goethite grains is well described by a simple mean field model. Exchange interactions between nanoparticles with different orientations of the easy axes can also result in a rotation of the sub-lattice magnetization directions.

/pdf/magnetic-interactions-between-nanoparticles-4ch65afwl2.pdf

Mikkel Fougt Hansen

Papers

Magnetic properties of hematite nanoparticles

Dynamics of an Interacting Particle System: Evidence of Critical Slowing Down

Magnetic interactions between nanoparticles.

Models for the dynamics of interacting magnetic nanoparticles

Estimation of blocking temperatures from ZFC/FC curves