Yan Levin

Bio: Yan Levin is an academic researcher from Universidade Federal do Rio Grande do Sul. The author has contributed to research in topics: Phase transition & Ionic bonding. The author has an hindex of 47, co-authored 238 publications receiving 7637 citations. Previous affiliations of Yan Levin include University of California, Santa Barbara & Pacific Northwest National Laboratory.

Electrostatic correlations: from plasma to biology

Abstract: Electrostatic correlations play an important role in physics, chemistry and biology. In plasmas they result in thermodynamic instability similar to the liquid–gas phase transition of simple molecular fluids. For charged colloidal suspensions the electrostatic correlations are responsible for screening and colloidal charge renormalization. In aqueous solutions containing multivalent counterions they can lead to charge inversion and flocculation. In biological systems the correlations account for the organization of cytoskeleton and the compaction of genetic material. In spite of their ubiquity, the true importance of electrostatic correlations has come to be fully appreciated only quite recently. In this paper, we will review the thermodynamic consequences of electrostatic correlations in a variety of systems ranging from classical plasmas to molecular biology.

Ions at the air-water interface: an end to a hundred-year-old mystery?

Abstract: Availability of highly reactive halogen ions at the surface of aerosols has tremendous implications for the atmospheric chemistry. Yet neither simulations, experiments, nor existing theories are able to provide a fully consistent description of the electrolyte-air interface. In this Letter a new theory is proposed which allows us to explicitly calculate the ionic density profiles, the surface tension, and the electrostatic potential difference across the solution-air interface. Predictions of the theory are compared to experiments and are found to be in excellent agreement. The theory also sheds new light on one of the oldest puzzles of physical chemistry---the Hofmeister effect.

Criticality in ionic fluids: Debye-Hückel theory, Bjerrum, and beyond.

Abstract: Debye-H\"uckel (DH) theory predicts phase separation in the primitive model electrolyte: hard spheres of diameter a with charges \ifmmode\pm\else\textpm\fi{}q. The coexistence curve (CC) is acceptable with ${\mathit{T}}_{\mathit{c}}^{\mathrm{*}}$\ensuremath{\equiv}${\mathit{k}}_{\mathit{B}}$${\mathit{T}}_{\mathit{c}}$a/${\mathit{q}}^{2}$=1/16, which is roughly correct, but the critical density, ${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}^{\mathrm{*}}$\ensuremath{\equiv}${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}$${\mathit{a}}^{3}$=1/64\ensuremath{\pi}, is far too low. Allowing for association into ideal dipolar pairs, following Bjerrum, improves ${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}$ and leaves ${\mathit{T}}_{\mathit{c}}$ unchanged but yields an unphysical CC. Extending DH theory to compute the dipole-ionic-fluid coupling yields a mean-field description with sensible CC and (${\mathit{T}}_{\mathit{c}}^{\mathrm{*}}$,${\mathrm{\ensuremath{\rho}}}_{\mathit{c}}^{\mathrm{*}}$) close to Monte Carlo based estimates: (0.057\ifmmode\pm\else\textpm\fi{}${1}_{5}$ , 0.030\ensuremath{\mp}8).

Criticality in the hard-sphere ionic fluid

Abstract: A physically based mean-field theory of criticality and phase separation in the restricted primitive model of an electrolyte (hard spheres of diameter a carrying charges ± q) is developed on the basis of the Debye-Huckel (DH) approach. Simple DH theory yields a critical point at T ∗ ≡ k B Ta/q 2 = 1 16 , which is only about 15% above the best recent simulation estimates ( T c,sim ∗ = 0.052–0.056 ) but a critical density ( ϱ c ∗ ≡ ϱ c a 3 = 1 64 π ⋍ 0.005 that is much too small ( ϱ c,sim ∗ = 0.023–0.035 ). Allowing for hard-core exclusion effects reduces these values slightly. However, correction of the DH linearization of the Poisson-Boltzmann equation by including pairing of + and − charges improves ϱ c ∗ significantly. Bjerrum's theory of the (required) association constant is revisited critically; Ebeling's reformulation is strongly endorsed but makes negligible numerical difference at criticality and below. The nature and size of the associated, dipolar ion pairs is examined quantitatively and their solvation free-energy in the residual fluid of free ions is calculated on the basis of DH theory. This contribution to the total free energy proves crucial and leads to a rather satisfactory description of the critical region. The temperature variation of the vapor pressure and of the density of neural dipolar pairs correlates fairly well with Gillan's numerical cluster analysis. Possible improvements to allow for larger ion clusters and to better represent the denser ionic liquid below criticality are discussed. Finally, the replacement of the DH approximation for the ionic free energy by the mean spherical approximation is studied. Reasonable critical densities are generated but the MSA critical temperatures are all 40–50% too high; in addition, the predicted density of neutral clusters seems much too low near criticality and, along with the vapor pressure, appears to decrease too rapidly by an exponential factor below Tc.

Polarizable ions at interfaces.

Abstract: A nonperturbative theory is presented which allows us to calculate the solvation free energy of polarizable ions near water-vapor and water-oil interfaces. The theory predicts that larger halogen anions are adsorbed at the interface, while the alkali metal cations are repelled from it. The density profiles calculated theoretically are similar to those obtained using molecular dynamics simulations with polarizable force fields.

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

Abstract: 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。

Monthly Notices of the Royal Astronomical Society

Abstract: Monthly Notices is one of the three largest general primary astronomical research publications. It is an international journal, published by the Royal Astronomical Society. This article 1 describes its publication policy and practice.

The collected works

Abstract: This is a review of Collected Works of John Tate. Parts I, II, edited by Barry Mazur and Jean-Pierre Serre. American Mathematical Society, Providence, Rhode Island, 2016. For several decades it has been clear to the friends and colleagues of John Tate that a “Collected Works” was merited. The award of the Abel Prize to Tate in 2010 added impetus, and finally, in Tate’s ninety-second year we have these two magnificent volumes, edited by Barry Mazur and Jean-Pierre Serre. Beyond Tate’s published articles, they include five unpublished articles and a selection of his letters, most accompanied by Tate’s comments, and a collection of photographs of Tate. For an overview of Tate’s work, the editors refer the reader to [4]. Before discussing the volumes, I describe some of Tate’s work. 1. Hecke L-series and Tate’s thesis Like many budding number theorists, Tate’s favorite theorem when young was Gauss’s law of quadratic reciprocity. When he arrived at Princeton as a graduate student in 1946, he was fortunate to find there the person, Emil Artin, who had discovered the most general reciprocity law, so solving Hilbert’s ninth problem. By 1920, the German school of algebraic number theorists (Hilbert, Weber, . . .) together with its brilliant student Takagi had succeeded in classifying the abelian extensions of a number field K: to each group I of ideal classes in K, there is attached an extension L of K (the class field of I); the group I determines the arithmetic of the extension L/K, and the Galois group of L/K is isomorphic to I. Artin’s contribution was to prove (in 1927) that there is a natural isomorphism from I to the Galois group of L/K. When the base field contains an appropriate root of 1, Artin’s isomorphism gives a reciprocity law, and all possible reciprocity laws arise this way. In the 1930s, Chevalley reworked abelian class field theory. In particular, he replaced “ideals” with his “idèles” which greatly clarified the relation between the local and global aspects of the theory. For his thesis, Artin suggested that Tate do the same for Hecke L-series. When Hecke proved that the abelian L-functions of number fields (generalizations of Dirichlet’s L-functions) have an analytic continuation throughout the plane with a functional equation of the expected type, he saw that his methods applied even to a new kind of L-function, now named after him. Once Tate had developed his harmonic analysis of local fields and of the idèle group, he was able prove analytic continuation and functional equations for all the relevant L-series without Hecke’s complicated theta-formulas. Received by the editors September 5, 2016. 2010 Mathematics Subject Classification. Primary 01A75, 11-06, 14-06. c ©2017 American Mathematical Society

Water desalination across nanoporous graphene

Abstract: We show that nanometer-scale pores in single-layer freestanding graphene can effectively filter NaCl salt from water. Using classical molecular dynamics, we report the desalination performance of such membranes as a function of pore size, chemical functionalization, and applied pressure. Our results indicate that the membrane’s ability to prevent the salt passage depends critically on pore diameter with adequately sized pores allowing for water flow while blocking ions. Further, an investigation into the role of chemical functional groups bonded to the edges of graphene pores suggests that commonly occurring hydroxyl groups can roughly double the water flux thanks to their hydrophilic character. The increase in water flux comes at the expense of less consistent salt rejection performance, which we attribute to the ability of hydroxyl functional groups to substitute for water molecules in the hydration shell of the ions. Overall, our results indicate that the water permeability of this material is several ...