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

Single-cycle THz radiation was generated by optical rectification of Yb-fiber laser pulses with 250 fs duration and 10 muJ energy. We obtained an average power of 0.5 mW at 1 MHz repetition rate.

Fiber laser pumped high average power single-cycle THz pulse source

A method to overcome limitations of conventional broadband terahertz generation techniques is presented. A stair-step echelon allows for the creation of superior tilted-pulse-fronts to yield larger frequencies and bandwidths, energy conversion efficiencies exceeding 5%.

Broadband terahertz generation with a stair-step echelon

We apply time-resolved interferometric imaging to study laser-driven focused shock waves on the microscale. Shock waves are generated in a 10 μm-thick layer of water by sub-nanosecond laser pulses focused into a ring of 100 μm radius. Imaging is performed with a Mach-Zehnder interferometer by time-delayed femtosecond pulses. We obtain a series of images tracing the converging shock wave as it collapses to a focal point and then reemerges as a divergent shock wave eventually leaving behind a cavitation bubble at the focus. Quantitative analysis of interferograms yields density and shock velocity values that match the water Hugoniot data found in the literature. In a separate development, we captured the propagation of cracks in a glass substrate initiated by focused shock waves. The results open the prospect of spatially resolved studies of shock-compressed materials in a small-scale all-optical experiment.

Interferometric analysis of cylindrically focused laser-driven shock waves in a thin liquid layer

A pedagogical review of optical spectroscopy and control at the “impulsive” limit, defined as a time scale faster than the fundamental vibrational or molecular motion under examination, is presented. Optical absorption and stimulated Raman scattering in this limit are seen to result in coherent vibrational motion in molecules and materials. A theoretical description of impulsive absorption and stimulated Raman scattering is followed by a survey of illustrative examples in which time-resolved observations of molecular and collective vibrational excitations are recorded. The topic then turns to optical control, beginning with a discussion of femtosecond pulse shaping through which complex ultrafast optical waveforms needed for many control objectives are produced. Theoretical formulations for optical control are reviewed, and a series of examples illustrating optical control over molecules and materials is presented.

Ultrafast Optical Spectroscopy and Optical Control

THz-induced optical birefringence was observed in the relaxor ferroelectrics KTN and KLTN. The dynamics observed may arise from the onset of ferroelectric nanodomains.

Keith A. Nelson

Papers

Fiber laser pumped high average power single-cycle THz pulse source

Broadband terahertz generation with a stair-step echelon

Interferometric analysis of cylindrically focused laser-driven shock waves in a thin liquid layer

Ultrafast Optical Spectroscopy and Optical Control

THz Kerr Effect in Relaxor Ferroelectrics