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

to be done in this area. Face recognition is a problem that scarcely clamoured for attention before the computer age but, having surfaced, has involved a wide range of techniques and has attracted the attention of some fine minds (David Mumford was a Fields Medallist in 1974). This singular application of mathematical modelling to a messy applied problem of obvious utility and importance but with no unique solution is a pretty one to share with students: perhaps, returning to the source of our opening quotation, we may invert Duncan's earlier observation, 'There is an art to find the mind's construction in the face!'.

Linear and nonlinear waves, by G. B. Whitham. Pp.636. £50. 1999. ISBN 0 471 35942 4 (Wiley).

To say that this is the best book on the quantum theory of fields is no praise, since to my knowledge it is the only book on this subject But it is a very good and most useful book The original was written in German and appeared in 1942 This is a translation with some minor changes A few remarks have been added, concerning meson theory and nuclear forces, also footnotes referring to modern work in this field, and finally an appendix on the symmetrization of the energy momentum tensor according to Belinfante Quantum Theory of Fields Prof Gregor Wentzel Translated from the German by Charlotte Houtermans and J M Jauch Pp ix + 224, (New York and London: Interscience Publishers, Inc, 1949) 36s

Quantum Theory of Fields

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

Water striders (Gerris remigis) have remarkable non-wetting legs that enable them to stand effortlessly and move quickly on water, a feature believed to be due to a surface-tension effect caused by secreted wax. We show here, however, that it is the special hierarchical structure of the legs, which are covered by large numbers of oriented tiny hairs (microsetae) with fine nanogrooves, that is more important in inducing this water resistance.

/pdf/biophysics-water-repellent-legs-of-water-striders-3a4p860uri.pdf

Biophysics: Water-repellent legs of water striders

We present the results of a numerical investigation of the emergence of chaos in the orbital dynamics of droplets walking on a vertically vibrating fluid bath and acted upon by one of the three different external forces, specifically, Coriolis, Coulomb, or linear spring forces. As the vibrational forcing of the bath is increased progressively, circular orbits destabilize into wobbling orbits and eventually chaotic trajectories. We demonstrate that the route to chaos depends on the form of the external force. When acted upon by Coriolis or Coulomb forces, the droplet's orbital motion becomes chaotic through a period-doubling cascade. In the presence of a central harmonic potential, the transition to chaos follows a path reminiscent of the Ruelle-Takens-Newhouse scenario.

/pdf/the-onset-of-chaos-in-orbital-pilot-wave-dynamics-1b4flu3s5h.pdf

The onset of chaos in orbital pilot-wave dynamics.

The ingenious methods employed by insects and spiders to move across a water surface rely on microphysics that is of little use to larger water walkers but of considerable interest to the microfluidics community.

Walking on water

A novel wake structure, observed as penny-shaped air bubbles rise
 at moderate Reynolds number through a thin layer of water bound between parallel glass
 plates inclined at a shallow angle relative to the horizontal, is reported. The
 structure of the wake is revealed through tracking particles suspended in the water.
 The wake completely encircles the rising bubble, and is characterized by a reverse
 surface flow or ‘edge jet’ which transports fluid in a thin
 boundary layer along the bubble surface from the tail to the nose at speeds which are typically an order of magnitude
 larger than the bubble rise speed. A consistent physical explanation for the wake structure
 is proposed. The wake is revealed to be a manifestation of the three-dimensionality
 of the flow in the suspending fluid. The bubble surface advances through a rolling
 motion, thus generating regions of surface divergence and convergence at, respectively,
 the leading and trailing edges of the bubble. A nose-to-tail gradient in
 surfactant concentration is thus established, and the associated surface tension gradient drives the
 edge jet. The dependence of the wake structure on the suspending fluid is examined experimentally. Surfactants play an anomalous role in the reported flow, serving to
 promote rather than suppress surface motions. The wake structure is an example of a mechanically
 forced Marangoni flow, and so represents a mechanical analogue of that
 accompanying thermocapillary drop motion in microgravity. A theoretical
 model is developed which reproduces the salient features of the flow, and on the basis of
 which an estimate is made of the mechanically induced surface tension gradient along the bubble surface.

The anomalous wake accompanying bubbles rising in a thin gap: a mechanically forced Marangoni flow

On a tweezer for droplets.

We present a macroscopic analog of an open quantum system, achieved with a classical pilot-wave system. Friedel oscillations are the angstrom-scale statistical signature of an impurity on a metal surface, concentric circular modulations in the probability density function of the surrounding electron sea. We consider a millimetric drop, propelled by its own wave field along the surface of a vibrating liquid bath, interacting with a submerged circular well. An ensemble of drop trajectories displays a statistical signature in the vicinity of the well that is strikingly similar to Friedel oscillations. The droplet trajectories reveal the dynamical roots of the emergent statistics. Our study elucidates a new mechanism for emergent quantum-like statistics in pilot-wave hydrodynamics and so suggests new directions for the nascent field of hydrodynamic quantum analogs.

https://advances.sciencemag.org/content/advances/6/20/eaay9234.full.pdf

John W. M. Bush

Papers

The onset of chaos in orbital pilot-wave dynamics.

Walking on water

The anomalous wake accompanying bubbles rising in a thin gap: a mechanically forced Marangoni flow

On a tweezer for droplets.

A hydrodynamic analog of Friedel oscillations.