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

Single-layer metal dichalcogenides are two-dimensional semiconductors that present strong potential for electronic and sensing applications complementary to that of graphene.

/pdf/electronics-and-optoelectronics-of-two-dimensional-2jbqr1unvw.pdf

Electronics and optoelectronics of two-dimensional transition metal dichalcogenides.

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Monolayer MoS2 has attracted significant attention owing to its excellent performance as an n‐type semiconductor from the transition metal dichalcogenide (TMDC) family. It is however strongly desired to develop controllable synthesis methods for 2D p‐type MoS2, which is crucial for complementary logic applications but remains difficult. In this work, high‐quality NbS2–MoS2 lateral heterostructures are synthesized by one‐step metal–organic chemical vapor deposition (MOCVD) together with monolayer MoS2 substitutionally doped by Nb, resulting in a p‐type doped behavior. The heterojunction shows a p‐type transfer characteristic with a high on/off current ratio of ≈104, exceeding previously reported values. The band structure through the NbS2–MoS2 heterojunction is investigated by density functional theory (DFT) and quantum transport simulations. This work provides a scalable approach to synthesize substitutionally doped TMDC materials and provides an insight into the interface between 2D metals and semiconductors in lateral heterostructures, which is imperative for the development of next‐generation nanoelectronics and highly integrated devices.

https://zenodo.org/record/7699115/files/Advanced%20Materials%20-%202023%20-%20Wang.pdf

Substitutional p‐Type Doping in NbS2–MoS2 Lateral Heterostructures Grown by MOCVD

Transition-metal dichalcogenide bilayers exhibit a rich exciton landscape including layer-hybridized excitons, i.e. excitons which are of partly intra- and interlayer nature. In this work, we study hybrid exciton–exciton interactions in naturally stacked WSe2 homobilayers. In these materials, the exciton landscape is electrically tunable such that the low-energy states can be rendered more or less interlayer-like depending on the strength of the external electric field. Based on a microscopic and material-specific many-particle theory, we reveal two intriguing interaction regimes: a low-dipole regime at small electric fields and a high-dipole regime at larger fields, involving interactions between hybrid excitons with a substantially different intra- and interlayer composition in the two regimes. While the low-dipole regime is characterized by weak inter-excitonic interactions between intralayer-like excitons, the high-dipole regime involves mostly interlayer-like excitons which display a strong dipole–dipole repulsion and give rise to large spectral blue-shifts and a highly anomalous diffusion. Overall, our microscopic study sheds light on the remarkable electrical tunability of hybrid exciton–exciton interactions in atomically thin semiconductors and can guide future experimental studies in this growing field of research.

https://pubs.rsc.org/en/content/articlepdf/2023/nr/d3nr01049j

Electrically tunable dipolar interactions between layer-hybridized excitons

Two-dimensional flat-band systems have recently attracted considerable interest due to the rich physics unveiled by emergent phenomena and correlated electronic states at van Hove singularities. However, the difficulties in electrically detecting the flat band position in field-effect structures are slowing down the investigation of their properties. In this work, we employ Indium Selenide (InSe) as a flat-band system due to a van Hove singularity at the valence band edge in a few-layer form of the material without the requirement of a twist angle. We investigate tunneling photocurrents in gated few-layer InSe structures and relate them to ambipolar transport and photoluminescence measurements. We observe an appearance of a sharp change in tunneling mechanisms due to the presence of the van Hove singularity at the flat band. We further corroborate our findings by studying tunneling currents as a reliable probe for the flat-band position up to room temperature. Our results create an alternative approach to studying flat-band systems in heterostructures of 2D materials.

Electrical detection of the flat band dispersion in van der Waals field-effect structures

Led by the rise of the internet of things, the world is experiencing exponential growth of generated data. Data-driven algorithms such as signal processing and artificial neural networks are required to process and extract meaningful information from it. They are, however, seriously limited by the traditional von-Neuman architecture with physical separation between processing and memory, motivating the development of in-memory computing. This emerging architecture is gaining attention by promising more energy-efficient computing on edge devices. In the past few years, two-dimensional materials have entered the field as a material platform suitable for realizing efficient memory elements for in-memory architectures. Here, we report a large-scale integrated 32x32 vector-matrix multiplier with 1024 floating-gate field-effect transistors (FGFET) that use monolayer MoS2 as the channel material. In our wafer-scale fabrication process, we achieve a high yield and low device-to-device variability, which are prerequisites for practical applications. A statistical analysis shows the potential for multilevel and analog storage with a single programming pulse, allowing our accelerator to be programmed using an efficient open-loop programming scheme. Next, we demonstrate reliable, discrete signal processing in a highly parallel manner. Our findings set the grounds for creating the next generation of in-memory processors and neural network accelerators that can take advantage of the full benefits of semiconducting van der Waals materials for non-von Neuman computing.

Large-Scale Integrated Vector-Matrix Multiplication Processor Based on Monolayer MoS2

While most neuromorphic systems are based on nanoscale electronic devices, nature relies on ions for energy-efficient information processing. Therefore, finding memristive nanofluidic devices is a milestone toward realizing electrolytic computers mimicking the brain down to its basic principles of operations. Here, we present a nanofluidic device designed for circuit scale in-memory processing that combines single-digit nanometric confinement and large entrance asymmetry. Our fabrication process is scalable while the device operates at the second timescale with a twenty-fold conductance ratio. It displays a switching threshold due to the dynamics of an extended space charge. The combination of these features permits assembling logic circuits composed of two interactive nanofluidic devices and an ohmic resistor. These results open the way to design multi-component ionic machinery, such as nanofluidic neural networks, and implementing brain-inspired ionic computations.

Andras Kis

Papers

Substitutional p‐Type Doping in NbS2–MoS2 Lateral Heterostructures Grown by MOCVD

Electrically tunable dipolar interactions between layer-hybridized excitons

Electrical detection of the flat band dispersion in van der Waals field-effect structures

Large-Scale Integrated Vector-Matrix Multiplication Processor Based on Monolayer MoS2

Ionic logic with highly asymmetric nanofluidic memristive switches