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

다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

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.

Li-ion battery technology has become very important in recent years as these batteries show great promise as power sources that can lead us to the electric vehicle (EV) revolution. The development of new materials for Li-ion batteries is the focus of research in prominent groups in the field of materials science throughout the world. Li-ion batteries can be considered to be the most impressive success story of modern electrochemistry in the last two decades. They power most of today's portable devices, and seem to overcome the psychological barriers against the use of such high energy density devices on a larger scale for more demanding applications, such as EV. Since this field is advancing rapidly and attracting an increasing number of researchers, it is important to provide current and timely updates of this constantly changing technology. In this review, we describe the key aspects of Li-ion batteries: the basic science behind their operation, the most relevant components, anodes, cathodes, electrolyte solutions, as well as important future directions for R&D of advanced Li-ion batteries for demanding use, such as EV and load-leveling applications.

Challenges in the development of advanced Li-ion batteries: a review

Nanocrystals are fundamental to modern science and technology. Mastery over the shape of a nanocrystal enables control of its properties and enhancement of its usefulness for a given application. Our aim is to present a comprehensive review of current research activities that center on the shape-controlled synthesis of metal nanocrystals. We begin with a brief introduction to nucleation and growth within the context of metal nanocrystal synthesis, followed by a discussion of the possible shapes that a metal nanocrystal might take under different conditions. We then focus on a variety of experimental parameters that have been explored to manipulate the nucleation and growth of metal nanocrystals in solution-phase syntheses in an effort to generate specific shapes. We then elaborate on these approaches by selecting examples in which there is already reasonable understanding for the observed shape control or at least the protocols have proven to be reproducible and controllable. Finally, we highlight a number of applications that have been enabled and/or enhanced by the shape-controlled synthesis of metal nanocrystals. We conclude this article with personal perspectives on the directions toward which future research in this field might take.

Shape‐Controlled Synthesis of Metal Nanocrystals: Simple Chemistry Meets Complex Physics?

Silver nanoparticles with an average size of ∼5 nm were deposited on the surface of preformed silica submicrospheres with the aid of power ultrasound. Ultrasound irradiation of a slurry of silica submicrospheres, silver nitrate, and ammonia in an aqueous medium for 90 min under an atmosphere of argon to hydrogen (95:5) yielded a silver−silica nanocomposite. By controlling the atmospheric and reaction conditions, we could achieve the deposition of metallic silver on the surface of the silica spheres. The resulting silver-deposited silica submicrosphere samples were characterized with X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, energy-dispersive X-ray analysis, high-resolution transmission electron microscopy, high-resolution scanning electron microscopy, photoacoustic spectroscopy, and Fourier transform infrared, UV−visible, and X-ray photoelectron spectroscopy.

Sonochemical Deposition of Silver Nanoparticles on Silica Spheres

Gold nanoparticles with an average size of ∼5 nm were deposited on the surface of preformed silica submicrospheres with the aid of power ultrasound. The sonochemical reduction was carried out by ultrasonic irradiation in an argon atmosphere at room temperature. Ultrasonic irradiation of a slurry of silica submicrospheres, chloroauric acid (HAuCl4), and ammonia in an aqueous medium for 45 min yielded a gold−silica nanocomposite. By controlling reaction conditions, we could achieve the deposition of metallic gold on the surface of the silica spheres. A unique crystallization process of the silica particles is observed. The crystallization process is assisted by the gold nanoparticles yielding the cristobalite phase of silica at a relatively low temperature. The resulting gold-deposited silica submicrosphere samples were characterized with XRD, EDAX, TEM, TGA, DSC, HR-SEM, and FT-IR, photoacoustic, and UV−visible spectroscopy.

Deposition of Gold Nanoparticles on Silica Spheres: A Sonochemical Approach

A one-step, eco-friendly ultrasound-assisted process is established for the rapid synthesis of sulfur-carbon composite cathode materials, avoiding the widely used, energy inefficient "melt-down" process for Li-S batteries. It is demonstrated that, without inserting sulfur into pores of carbon, the coulombic efficiency of SC/Li cell in the new DOL/D2 electrolyte is greater than 96% for 100 cycles, which is far superior to the reported numerous electrolyte formulations.

Ultrasound assisted design of sulfur/carbon cathodes with partially fluorinated ether electrolytes for highly efficient Li/S batteries.

Improving the high-temperature performance of LiMn2O4 spinel electrodes by coating the active mass with MgO via a sonochemical method

Carbon nanofibers produced by electrospinning of polyacrylonitrile polymer and subsequent carbonization were tested as freestanding potassium-ion anodes. The effect of oxygen functionalization on K-ion carbon anode performance was tested for the first time via plasma oxidation of prepared carbon nanofibers. The produced materials exhibited exceptional cycling stability through the amorphous carbon structuring and one-dimensional architecture accommodating significant material expansion upon K+ intercalation, resulting in a stable capacity of 170 mAh g–1 after 1900 cycles at 1C rate for N-rich carbon nanofibers. Excellent rate performance of 110 mAh g–1 at 10C rate, as compared to 230 mAh g–1 at C/10 rate, resulted from the K-ion surface storage mechanism and the increased K+ solid diffusion coefficient in carbon nanofibers as compared to graphite. Plasma oxidation treatment augmented surface storage of K+ by oxygen functionalities but increased material charge transfer resistance as compared to N-rich car...

Vilas G. Pol

Papers

Sonochemical Deposition of Silver Nanoparticles on Silica Spheres

Deposition of Gold Nanoparticles on Silica Spheres: A Sonochemical Approach

Ultrasound assisted design of sulfur/carbon cathodes with partially fluorinated ether electrolytes for highly efficient Li/S batteries.

Improving the high-temperature performance of LiMn2O4 spinel electrodes by coating the active mass with MgO via a sonochemical method

Binder-Free N- and O-Rich Carbon Nanofiber Anodes for Long Cycle Life K-Ion Batteries.