There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

SciPy is an open source scientific computing library for the Python programming language. SciPy 1.0 was released in late 2017, about 16 years after the original version 0.1 release. SciPy has become a de facto standard for leveraging scientific algorithms in the Python programming language, with more than 600 unique code contributors, thousands of dependent packages, over 100,000 dependent repositories, and millions of downloads per year. This includes usage of SciPy in almost half of all machine learning projects on GitHub, and usage by high profile projects including LIGO gravitational wave analysis and creation of the first-ever image of a black hole (M87). The library includes functionality spanning clustering, Fourier transforms, integration, interpolation, file I/O, linear algebra, image processing, orthogonal distance regression, minimization algorithms, signal processing, sparse matrix handling, computational geometry, and statistics. In this work, we provide an overview of the capabilities and development practices of the SciPy library and highlight some recent technical developments.

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SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python

Summary form only givenIn recent years there has been increasing interest in the use of quasi-phase-matched periodically poled lithium niobate (PPLN) for a variety of frequency conversion applications We investigate the influence of of MgO doping on the green-induced infrared absorption, photorefraction, and ferroelectric domain nature in near stoichiometric LiNbO/sub 3/, and MgO doped near-stoichiometric LiNbO/sub 3/ are expected to show much improved nonlinear properties since they have considerably reduced photorefraction, and ferroelectric domain switching compared to congruent crystals

Improved material properties in MgO-doped near-stoichiometric LiNbO/sub 3/ for nonlinear optical applications

Photothermal common-path interferometry has been used to measure optical absorption at 1064 nm and at 514 nm in high purity sapphire crystals. In as-grown and hydrogen-annealed material, uniform optical absorptions of 40–50 ppm/cm were found throughout. In a sample that had been oxygen-annealed after polishing, spatial variations in absorption and scattering/fluorescence revealed a −4 mm thick ‘skin’ of lossy material surrounding a core having lower losses typical of as-grown material. A ‘valley’ with optical absorption about 2–4 times lower than as-grown material (at both 1064 nm and 514 nm) was found at the interface between the oxidized surface layer and the core. The mechanism by which the ‘valley’ formed is not known, but it does suggest that a better understanding of the oxidation process may lead to a reduction in the optical absorption of sapphire crystals.

Effect of annealing on the light absorption in sapphire

Nonlinear interactions between elastic waves and ferroelastic domain walls offer the possibility of setting up and electronically controlling periodic domain gratings for application as tunable diffraction gratings, acoustic wave filters and surface acoustic wave transducers. Estimates of the practicality of using this control mechanism are presented for neodymium pentaphosphate.

Elastic nonlinearity and domain wall motion in ferroelastic crystals

We demonstrate a guided-wave degenerate OPO comprising a PPLN waveguide and a polarization-maintaining optical fiber. The output frequency comb centered at 1548 nm is ∼75-times broader than the pump and is phase locked to it.

Guided-wave half-harmonic generation of frequency combs with ∼75-fold spectral broadening

We have fabricated low optical loss diffusion bonded stacked (DBS) GaAs and demonstrated that mid-infrared radiation as long as 17 /spl mu/m could be generated by difference frequency mixing with DBS GaAs.

Martin M. Fejer

Papers

Improved material properties in MgO-doped near-stoichiometric LiNbO/sub 3/ for nonlinear optical applications

Effect of annealing on the light absorption in sapphire

Elastic nonlinearity and domain wall motion in ferroelastic crystals

Guided-wave half-harmonic generation of frequency combs with ∼75-fold spectral broadening

16-micron infrared generation by difference-frequency mixing in diffusion-bonded-stacked GaAs