There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Ordered magnetic nanostructures: fabrication and properties

A highly sensitive tactile sensor is devised by applying microstructured graphene arrays as sensitive layers. The combination of graphene and anisotropic microstructures endows this sensor with an ultra-high sensitivity of -5.53 kPa(-1) , an ultra-fast response time of only 0.2 ms, as well as good reliability, rendering it promising for the application of tactile sensing in artificial skin and human-machine interface.

Microstructured Graphene Arrays for Highly Sensitive Flexible Tactile Sensors

Two dimensional electrons in a lateral magnetic superlattice

High mobility two-dimensional electron gases (2DEG) with mean free paths in excess of several microns allow the effects of a small potential modulation to dominate in the resistivity [1,2]. Recent advances in nanofabrication allow microstructured magnetic potentials to be applied to ballistic electron systems. Microscopic magnetic barriers with amplitude of several thousand gauss were formed in nonplanar devices [3] or by gating a 2DEG with micromagnets [4 – 6] or superconductors [7]. The influence of a magnetic modulation on ballistic electrons was demonstrated experimentally via commensurability effects between the classical cyclotron diameter and the period of a magnetic superlattice [4,5,7]. These findings have since been generalized to 2D superlattices [8] and composite fermion systems [9]. An interesting situation arises when the sign of the magnetic modulation and therefore the Lorentz force alternates. In addition to conferring a drift to the cyclotron guiding center, the magnetic gradient confines electrons about the boundary line between two regions of opposite magnetic field [4,10]. Recent theoretical developments have focused on the energy spectrum and the physical properties of electrons quantum mechanically confined in this way [11]. Sharp resonances in the magnetization [12] and conductance [13] of a magnetic antidot have been associated with the formation of novel magnetic edge states circulating clockwise and anticlockwise about the antidot. In this Letter, we investigate the magnetoresistance of 2D electrons confined by a transverse magnetic field gradient. A sharp peak is observed when the applied magnetic field cancels the modulation field. On either side of this peak, transport is controlled by one of the two magnetic edge states predicted in Refs. [12] and [13]. The effects of varying the magnetic gradient and the electron density confirm this picture. The dependencies of Rxx and Rxy are both modeled within a straightforward drift-diffusion theory. Our data show that in the presence of a strongly inhomogeneous current distribution the Hall resistance is not proportional to the magnetic field averaged over the Hall junction. The experiments were performed on a standard GaAs Al0.3Ga0.7As heterojunction with electron density ns 1.94 3 10 15 m 22 , and mean free path l 4.5 m ma t

/pdf/resistance-resonance-effects-through-magnetic-edge-states-1i4sajhmv9.pdf

Resistance resonance effects through magnetic edge states.

A single-barrier GaAs/AlAs/GaAs heterostructure, with self-assembled In-based quantum dots incorporated in the AlAs tunnel barrier, exhibits a series of resonant peaks in the low temperature current‐voltage characteristics. We argue that each peak arises from singleelectron tunneling through the discrete zero-dimensionalstate of an individual InAs dot. We use the tunneling for fine probing of the local density of states in the emitter-accumulation layer. Landau-quantized states are resolved at magnetic field Bk I as low as 0.2 T. Spinsplitting of the dot electron states has been observed for B? I . c 1997 Academic Press Limited

/pdf/resonant-magnetotunneling-through-individual-self-assembled-4rupwvqrky.pdf

Resonant magnetotunneling through individual self-assembled InAs quantum dots.

This review explores the dynamics of two-dimensional electrons in magnetic potentials that vary on scales smaller than the mean free path. The physics of microscopically inhomogeneous magnetic fields relates to important fundamental problems in the fractional quantum Hall effect, superconductivity, spintronics and graphene physics and spins out promising applications which will be described here. After introducing the initial work done on electron localization in random magnetic fields, the experimental methods for fabricating magnetic potentials are presented. Drift-diffusion phenomena are then described, which include commensurability oscillations, magnetic channelling, resistance resonance effects and magnetic dots. We then review quantum phenomena in magnetic potentials including magnetic quantum wires, magnetic minibands in superlattices, rectification by snake states, quantum tunnelling and Klein tunnelling. The third part is devoted to spintronics in inhomogeneous magnetic fields. This covers spin filtering by magnetic field gradients and circular magnetic fields, electrically induced spin resonance, spin resonance fluorescence and coherent spin manipulation.

https://iopscience.iop.org/article/10.1088/0953-8984/22/25/253201/pdf

Electron dynamics in inhomogeneous magnetic fields.

Recent results demonstrate techniques for fully quantitative, statistical inference of the dynamics of individual neurons under the Hodgkin---Huxley framework of voltage-gated conductances. Using a variational approximation, this approach has been successfully applied to simulated data from model neurons. Here, we use this method to analyze a population of real neurons recorded in a slice preparation of the zebra finch forebrain nucleus HVC. Our results demonstrate that using only 1,500 ms of voltage recorded while injecting a complex current waveform, we can estimate the values of 12 state variables and 72 parameters in a dynamical model, such that the model accurately predicts the responses of the neuron to novel injected currents. A less complex model produced consistently worse predictions, indicating that the additional currents contribute significantly to the dynamics of these neurons. Preliminary results indicate some differences in the channel complement of the models for different classes of HVC neurons, which accords with expectations from the biology. Whereas the model for each cell is incomplete (representing only the somatic compartment, and likely to be missing classes of channels that the real neurons possess), our approach opens the possibility to investigate in modeling the plausibility of additional classes of channels the cell might possess, thus improving the models over time. These results provide an important foundational basis for building biologically realistic network models, such as the one in HVC that contributes to the process of song production and developmental vocal learning in songbirds.

/pdf/estimating-parameters-and-predicting-membrane-voltages-with-24p4ira67r.pdf

Alain Nogaret

Papers

Two dimensional electrons in a lateral magnetic superlattice

Resistance resonance effects through magnetic edge states.

Resonant magnetotunneling through individual self-assembled InAs quantum dots.

Electron dynamics in inhomogeneous magnetic fields.

Estimating parameters and predicting membrane voltages with conductance-based neuron models