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

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’

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

We provide an overview of the terahertz (THz) polaritonics system, an on-chip platform for the generation, detection, and control of THz-frequency electromagnetic waves. The “chip” is a thin slab of lithium niobate crystal whose nonlinear and electro-optic properties directly enable the functionality. We first discuss dielectric slab waveguiding, which determines THz wave behavior in the polaritonics system. We then cover the generation of broadband and narrowband THz waves with an ultrafast laser pulse. The next topic is time-resolved imaging, which lets us record movies of the THz waves as they propagate at the speed of light with sub-cycle temporal and λ/100 spatial resolution. The final experimental tool discussed is laser machining, which makes it possible to fabricate photonic elements directly in the lithium niobate slab. Using these techniques, we show THz waves interacting with a variety of microstructures including a mirror, diffraction grating, waveguide, interferometer, photonic crystal, and metal antenna. These structures enable wave steering, guiding, spectral and spatial filtering, amplitude modulation, field enhancement, and sub-wavelength field localization. The broad capability set makes the polaritonics platform a promising one for future high-speed devices in optical communications and computation. The field enhancement and control also makes this an excellent platform for nonlinear THz spectroscopy.

The LiNbO 3 Slab Waveguide: A Platform for Terahertz Signal Generation, Detection, and Control

Terahertz field–induced ferroelectricity in quantum paraelectric SrTiO[subscript 3]

The glass-forming aqueous electrolyte LiCl/H2O (13 mol%) was studied using impulsive stimulated light scattering, a time delayed four-wave mixing (‘transient grating’) technique. The excitation pulses deposit heat in the sample through weak optical absorption, and the time-dependent density response of the sample is monitored by variably delayed probe pulses. In most viscoelastic samples, longitudinal acoustic waves (the transient density response) and gradual thermal expansion (leading to a steady-state density response which eventually decays due to thermal diffusion) were observed. In LiCl/H2O an additional and unusual response was observed. Thermal expansion is followed by contraction on a timescale much faster than that of thermal diffusion. Possible microscopic origins of this response are suggested.

Preliminary impulsive stimulated light scattering study of the glass-forming liquid LiCl/H2O: evidence for unusual structural relaxation dynamics

Strong coupling between light and matter occurs when the two interact strongly enough to form new hybrid modes called polaritons. Here we report on the strong coupling of both the electric and magnetic degrees of freedom to an ultrafast terahertz (THz) frequency electromagnetic wave. In our system, optical phonons in a slab of ferroelectric lithium niobate (LiNbO$_3$) are strongly coupled to a THz electric field to form phonon-polaritons, which are simultaneously strongly coupled to magnons in an adjacent slab of canted antiferromagnetic erbium orthoferrite (ErFeO$_3$) via the THz magnetic field. The strong coupling leads to the formation of new magnon-phonon-polariton modes, which we experimentally observe in the wavevector-frequency dispersion curve as an avoided crossing and in the time-domain as a normal-mode beating. Our simple yet versatile on-chip waveguide platform provides a promising avenue by which to explore both ultrafast THz spintronics applications and the quantum nature of the interaction.

Keith A. Nelson

Papers

The LiNbO 3 Slab Waveguide: A Platform for Terahertz Signal Generation, Detection, and Control

Terahertz field–induced ferroelectricity in quantum paraelectric SrTiO[subscript 3]

Preliminary impulsive stimulated light scattering study of the glass-forming liquid LiCl/H2O: evidence for unusual structural relaxation dynamics

Terahertz-frequency magnon-phonon-polaritons in the strong coupling regime

Structural Relaxation of Supercooled Liquids from Impulsive Stimulated Light Scattering