Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

A hyperbranched semiconductor nanocrystal particle, which includes a first arm, where the first arm has an intermediate portion and opposing terminal portions, and a second arm, extending from the intermediate portion of the first arm.

Hybrid solar cells with 3-dimensional hyperbranched nanocrystals

In situ electron microscopy is used to observe the morphological evolution of cadmium selenide nanorods as they sublime under vacuum at a series of elevated temperatures. Mass loss occurs anisotropically along the nanorod’s long axis. At temperatures close to the sublimation threshold, the phase change occurs from both tips of the nanorods and proceeds unevenly with periods of rapid mass loss punctuated by periods of relative stability. At higher temperatures, the nanorods sublime at a faster, more uniform rate, but mass loss occurs from only a single end of the rod. We propose a mechanism that accounts for the observed sublimation behavior based on the terrace–ledge–kink (TLK) model and how the nanorod surface chemical environment influences the kinetic barrier of sublimation.

/pdf/in-situ-transmission-electron-microscopy-of-cadmium-selenide-1hmh6hvml7.pdf

In Situ Transmission Electron Microscopy of Cadmium Selenide Nanorod Sublimation

The processing of Kevlar to certain strengths by hot-drawing can benefit by quantitative understanding of the correlation between structural and mechanical properties during the pre-drawing process. Here, we use a novel continuous dynamic analysis (CDA) to monitor the evolution in storage modulus and loss factor of Kevlar 49 fibers as a function of strain via a quasi-static tensile test. Unlike traditional dynamic mechanical analysis, CDA allows the tracking of strain-dependent mechanical properties until failure. The obtained dynamic viscoelastic properties of Kevlar 49 are correlated with structural data obtained from synchrotron radiation analysis and with Raman scattering frequencies. Rate-dependent stress–strain results from Kevlar are compared to Nomex, spider silk, polyester and rubber, and provide insight into how the mechanical properties of Kevlar originate from its characteristic structural features. We find that as the storage modulus of Kevlar is essentially equal to the Young's modulus, the measured quantitative relationships between storage modulus and strain can provide insights into the tuning of the mechanical properties of aramid materials for specific applications.

https://escholarship.org/content/qt115658gp/qt115658gp.pdf?t=p0uuxv

Strain-dependent dynamic mechanical properties of Kevlar to failure: Structural correlations and comparisons to other polymers

A photovoltaic device having a first electrode layer, a high resistivity transparent film disposed on the first electrode, a second electrode layer, and an inorganic photoactive layer disposed between the first and second electrode layers, wherein the inorganic photoactive layer is disposed in at least partial electrical contact with the high resistivity transparent film, and in at least partial electrical contact with the second electrode. The photoactive layer has a first inorganic material and a second inorganic material different from the first inorganic material, wherein the first and second inorganic materials exhibit a type II band offset energy profile, and wherein the photoactive layer has a first population of nanostructures of a first inorganic material and a second population of nanostructures of a second inorganic material.

A. Paul Alivisatos

Papers

Hybrid solar cells with 3-dimensional hyperbranched nanocrystals

In Situ Transmission Electron Microscopy of Cadmium Selenide Nanorod Sublimation

Strain-dependent dynamic mechanical properties of Kevlar to failure: Structural correlations and comparisons to other polymers

Nanocrystal solar cells processed from solution

Welcome toNano Letters