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

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

Exchange bias in nanostructures

We employ scanning probe microscopy to reveal atomic structures and nanoscale morphology of graphene-based electronic devices (i.e., a graphene sheet supported by an insulating silicon dioxide substrate) for the first time. Atomic resolution scanning tunneling microscopy images reveal the presence of a strong spatially dependent perturbation, which breaks the hexagonal lattice symmetry of the graphitic lattice. Structural corrugations of the graphene sheet partially conform to the underlying silicon oxide substrate. These effects are obscured or modified on graphene devices processed with normal lithographic methods, as they are covered with a layer of photoresist residue. We enable our experiments by a novel cleaning process to produce atomically clean graphene sheets.

/pdf/atomic-structure-of-graphene-on-sio2-wse0owhlg7.pdf

Atomic Structure of Graphene on SiO2

Equilibrium wetting on rough surfaces is discussed in terms of the “competition” between complete liquid penetration into the roughness grooves and entrapment of air bubbles inside the grooves underneath the liquid. The former is the homogeneous wetting regime, usually described by the Wenzel equation. The latter is the heterogeneous wetting regime that is described by the Cassie−Baxter equation. Understanding this “competition” is essential for the design of ultrahydrophobic surfaces. The present discussion puts the Wenzel and Cassie−Baxter equations into proper mathematical−thermodynamic perspective and defines the conditions for determining the transition between the homogeneous and heterogeneous wetting regimes. In particular, a new condition that is necessary for the existence of the heterogeneous wetting regime is added. It is demonstrated that when this condition is violated, the homogeneous wetting regime is in effect, even though the Cassie−Baxter equation may be satisfied.

Wetting on Hydrophobic Rough Surfaces: To Be Heterogeneous or Not To Be?

Aqueous ion-containing interfaces are ubiquitous and play a key role in a plethora of physical, chemical, atmospheric, and biological processes, from which we mention just a few illustrative examples: (i) Ions at the air/water interface are important for atmospheric chemistry involving ocean surfaces and seawater aerosols, 1-5 as well as that of the Arctic snowpack covered by sea spray. 6,7 (ii) Many salts (such as NaCl) tend to inhibit bubble coalescence, 8-12 which is one of the reasons why foam is formed when waves break in the ocean but not in freshwater lakes. (iii) Brine rejection occurring at the seawater/ice interface has profound climatic effects in polar regions. 13 (iv) The aqueous electrolyte/metal interface is involved in electrode and corrosion processes. 14,15

Specific ion effects at the air/water interface.

The outer surface of the facet lenses in the compound eyes of moths consists of an array of excessive cuticular protuberances, termed corneal nipples. We have investigated the moth-eye corneal nipple array of the facet lenses of 19 diurnal butterfly species by scanning electron microscopy, transmission electron microscopy and atomic force microscope, as well as by optical modelling. The nipples appeared to be arranged in domains with almost crystalline, hexagonal packing. The nipple distances were found to vary only slightly, ranging from about 180 to 240 nm, but the nipple heights varied between 0 (papilionids) and 230 nm (a nymphalid), in good agreement with previous work. The nipples create an interface with a gradient refractive index between that of air and the facet lens material, because their distance is distinctly smaller than the wavelength of light. The gradient in the refractive index was deduced from effective medium theory. By dividing the height of the nipple layer into 100 thin slices, an optical multilayer model could be applied to calculate the reflectance of the facet lenses as a function of height, polarization and angle of incidence. The reflectance progressively diminished with increased nipple height. Nipples with a paraboloid shape and height 250 nm, touching each other at the base, virtually completely reduced the reflectance for normally incident light. The calculated dependence of the reflectance on polarization and angle of incidence agreed well with experimental data, underscoring the validity of the modelling. The corneal nipples presumably mainly function to reduce the eye glare of moths that are inactive during the day, so to make them less visible for predators. Moths are probably ancestral to the diurnal butterflies, suggesting that the reduced size of the nipples of most butterfly species indicates a vanishing trait. This effect is extreme in papilionids, which have virtually absent nipples, in line with their highly developed status. A similar evolutionary development can be noticed for the tapetum of the ommatidia of lepidopteran eyes. It is most elaborate in moth-eyes, but strongly reduced in most diurnal butterflies and absent in papilionids.

/pdf/light-on-the-moth-eye-corneal-nipple-array-of-butterflies-39l88lsbgw.pdf

Light on the moth-eye corneal nipple array of butterflies

Theoretical expressions for the height-height correlation function of self-affine fractal surfaces are discussed in comparison with scanning tunneling microscopy, correlation and surface-width data obtained from rough silver and gold films. Fourier transformations are used to compare with equilibrium phenomena, and lead to a correlation model with an associated roughness spectrum of analytic form.

/pdf/roughness-spectrum-and-surface-width-of-self-affine-fractal-4nwh4h02rm.pdf

Roughness spectrum and surface width of self-affine fractal surfaces via the K-correlation model.

Experimental observations of self-affine scaling and kinetic roughening at sub-micron length scales are reviewed for thin solid films and ion-beam eroded surfaces.

/pdf/experimental-observations-of-self-affine-scaling-and-kinetic-4kqvofzk5f.pdf

Experimental Observations of Self-Affine Scaling and Kinetic Roughening at Sub-Micron Lengthscales

Effects of surface roughness on electrical properties of a thin insulating film capacitor with one smooth electrode plate and one rough electrode plate are investigated. The electrode plate roughness is described in terms of self-affine fractal scaling through the roughness exponent \ensuremath{\alpha}, the root-mean square (rms) roughness amplitude w, and the correlation length \ensuremath{\xi}. The electric field, capacitance, and leakage current show similar qualitative changes with the roughness parameters: they all increase as w increases, and also increase as either \ensuremath{\xi} or \ensuremath{\alpha} decreases.

/pdf/surface-roughness-effect-on-capacitance-and-leakage-current-23b8uqxqic.pdf

Surface-roughness effect on capacitance and leakage current of an insulating film

We study the effect of surface roughness on magnetic domain wall thickness, domain size, and coercivity of thin magnetic films. We show that the roughness increases (decreases) the domain wall thickness and domain size for Bloch walls (Neel walls). The surface roughness affects the domain wall movement and causes the increase of coercivity for Neel walls. The coercivity due to domain rotation for Bloch walls decreases with the increase of roughness. The domain wall thickness, domain size, and coercivity are each related to the demagnetizing factor, which depends on the roughness and type of wall (Bloch wall or Neel wall). The calculated coercivity versus thickness is compared with experimental data of ultrathin Co films, where the thickness dependent roughness parameters are available.

/pdf/effect-of-surface-roughness-on-magnetic-domain-wall-4de24psraf.pdf

Georgios Palasantzas

Papers

Light on the moth-eye corneal nipple array of butterflies

Roughness spectrum and surface width of self-affine fractal surfaces via the K-correlation model.

Experimental Observations of Self-Affine Scaling and Kinetic Roughening at Sub-Micron Lengthscales

Surface-roughness effect on capacitance and leakage current of an insulating film

Effect of surface roughness on magnetic domain wall thickness, domain size, and coercivity