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

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

BACKGROUND Materials by design is an appealing idea that is very hard to realize in practice. Combining the best of different ingredients in one ultimate material is a task for which we currently have no general solution. However, we do have some successful examples to draw upon: Composite materials and III-V heterostructures have revolutionized many aspects of our lives. Still, we need a general strategy to solve the problem of mixing and matching crystals with different properties, creating combinations with predetermined attributes and functionalities. ADVANCES Two-dimensional (2D) materials offer a platform that allows creation of heterostructures with a variety of properties. One-atom-thick crystals now comprise a large family of these materials, collectively covering a very broad range of properties. The first material to be included was graphene, a zero-overlap semimetal. The family of 2D crystals has grown to includes metals (e.g., NbSe 2 ), semiconductors (e.g., MoS 2 ), and insulators [e.g., hexagonal boron nitride (hBN)]. Many of these materials are stable at ambient conditions, and we have come up with strategies for handling those that are not. Surprisingly, the properties of such 2D materials are often very different from those of their 3D counterparts. Furthermore, even the study of familiar phenomena (like superconductivity or ferromagnetism) in the 2D case, where there is no long-range order, raises many thought-provoking questions. A plethora of opportunities appear when we start to combine several 2D crystals in one vertical stack. Held together by van der Waals forces (the same forces that hold layered materials together), such heterostructures allow a far greater number of combinations than any traditional growth method. As the family of 2D crystals is expanding day by day, so too is the complexity of the heterostructures that could be created with atomic precision. When stacking different crystals together, the synergetic effects become very important. In the first-order approximation, charge redistribution might occur between the neighboring (and even more distant) crystals in the stack. Neighboring crystals can also induce structural changes in each other. Furthermore, such changes can be controlled by adjusting the relative orientation between the individual elements. Such heterostructures have already led to the observation of numerous exciting physical phenomena. Thus, spectrum reconstruction in graphene interacting with hBN allowed several groups to study the Hofstadter butterfly effect and topological currents in such a system. The possibility of positioning crystals in very close (but controlled) proximity to one another allows for the study of tunneling and drag effects. The use of semiconducting monolayers leads to the creation of optically active heterostructures. The extended range of functionalities of such heterostructures yields a range of possible applications. Now the highest-mobility graphene transistors are achieved by encapsulating graphene with hBN. Photovoltaic and light-emitting devices have been demonstrated by combining optically active semiconducting layers and graphene as transparent electrodes. OUTLOOK Currently, most 2D heterostructures are composed by direct stacking of individual monolayer flakes of different materials. Although this method allows ultimate flexibility, it is slow and cumbersome. Thus, techniques involving transfer of large-area crystals grown by chemical vapor deposition (CVD), direct growth of heterostructures by CVD or physical epitaxy, or one-step growth in solution are being developed. Currently, we are at the same level as we were with graphene 10 years ago: plenty of interesting science and unclear prospects for mass production. Given the fast progress of graphene technology over the past few years, we can expect similar advances in the production of the heterostructures, making the science and applications more achievable.

2D materials and van der Waals heterostructures

Experimental study of large-scale stiffened thin-walled CFDST columns under aixal compression

CFAP45, a heterotaxy and congenital heart disease gene, affects cilia stability.

Limb-girdle muscular dystrophy (LGMD), a rare group of non-congenital inherited muscle diseases, is characterized by a progressive reduction in muscle tone and force of the proximal limbs. The clinical manifestations and genetic patterns of LGMD are heterogeneous. This study reported on a 10-year-old male patient with LGMD type 2U who experienced muscle weakness in the lower limbs after exercise. Upon admission, the patient's creatine kinase levels were significantly elevated, and hydration and alkalinization therapy were ineffective. Using high-throughput sequencing, muscular dystrophy-related genes were tested in the patient, his parents, and his sister. The patient was found to have a heterozygous deletion of exon 9 of the ISPD gene and a heterozygous missense mutation c.1231C>T (p.Leu411Phe). The patient's father carried the heterozygous missense mutation c.1231C>T (p.Leu411Phe) of the ISPD gene, while his mother and sister carried a heterozygous deletion of exon 9 of the ISPD gene. These mutations have not been reported in existing databases or literature. Conservation and protein structure prediction analyses of the mutation sites indicated that they are highly conserved and located in the C-terminal domain of the ISPD protein, which may affect protein function. Based on the above results and relevant clinical data, the patient was definitively diagnosed with LGMD type 2U. This study enriched the spectrum of ISPD gene mutations by summarizing the patient's clinical characteristics and analyzing new ISPD gene variations. This can aid in the early diagnosis and genetic counseling of the disease.

Diagnosis and genetic testing analysis of limb-girdle muscular dystrophy type 2U caused by a compound heterozygous mutation in the ISPD gene.

Electronic properties of super-atomic crystals are far from being well explored in the case of their versatile building units and premature understanding of their inter-unit couplings. Here, we experiment-theory jointly investigated a rational-designed layered super-atomic crystal of Au6Te12Se8 cubes, stacked through non-covalent inter-cube quasi-bonds. We found a sequential-emerged anisotropic triple-cube charge-density-wave and spatially polarized metallic states below 120 K, as examined using scanning tunneling microscopy/spectroscopy, angle-resolved photoemission spectroscopy, transport measurement, Raman spectra and density functional theory. The polarized states are locked in an anti-parallel configuration, required by maintaining the inversion symmetry of the center-cube of a tri-cube group. The anti-polar metallic states are thus interweaved by the charge density wave and the polarized metallic states, primarily ascribed to electronic effects rather than atomic displacements. This work demonstrated that strong electronic interactions could play an essential role in determining electronic properties of non-covalent super-atomic solids, which shed considerable light on expanding the existing category of quantum materials to non-covalent solids.

Wei Ji

Papers

Experimental study of large-scale stiffened thin-walled CFDST columns under aixal compression

CFAP45, a heterotaxy and congenital heart disease gene, affects cilia stability.

Diagnosis and genetic testing analysis of limb-girdle muscular dystrophy type 2U caused by a compound heterozygous mutation in the ISPD gene.

Interweaving polar charge orders in a layered metallic super-atomic.

A porphyrin-based ratiometric SERS sensor for high-throughput and ultrasensitive cadmium ion detection.