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

▪ Abstract Plant responses to salinity stress are reviewed with emphasis on molecular mechanisms of signal transduction and on the physiological consequences of altered gene expression that affect biochemical reactions downstream of stress sensing. We make extensive use of comparisons with model organisms, halophytic plants, and yeast, which provide a paradigm for many responses to salinity exhibited by stress-sensitive plants. Among biochemical responses, we emphasize osmolyte biosynthesis and function, water flux control, and membrane transport of ions for maintenance and re-establishment of homeostasis. The advances in understanding the effectiveness of stress responses, and distinctions between pathology and adaptive advantage, are increasingly based on transgenic plant and mutant analyses, in particular the analysis of Arabidopsis mutants defective in elements of stress signal transduction pathways. We summarize evidence for plant stress signaling systems, some of which have components analogous to t...

Plant cellular and molecular responses to high salinity.

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abiotic Stress Signaling and Responses in Plants

Nonpathogenic rhizobacteria can induce a systemic resistance in plants that is phenotypically similar to pathogen-induced systemic acquired resistance (SAR). Rhizobacteria-mediated induced systemic resistance (ISR) has been demonstrated against fungi, bacteria, and viruses in Arabidopsis, bean, carnation, cucumber, radish, tobacco, and tomato under conditions in which the inducing bacteria and the challenging pathogen remained spatially separated. Bacterial strains differ in their ability to induce resistance in different plant species, and plants show variation in the expression of ISR upon induction by specific bacterial strains. Bacterial determinants of ISR include lipopolysaccharides, siderophores, and salicylic acid (SA). Whereas some of the rhizobacteria induce resistance through the SA-dependent SAR pathway, others do not and require jasmonic acid and ethylene perception by the plant for ISR to develop. No consistent host plant alterations are associated with the induced state, but upon challenge inoculation, resistance responses are accelerated and enhanced. ISR is effective under field conditions and offers a natural mechanism for biological control of plant disease.

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Systemic resistance induced by rhizosphere bacteria

The evaluation of the wavelength parameters of spaceborne oceanic lidar is of great importance to ensure that the lidar system can provide more information of ocean and can be realized in engineering. In this paper, the optimum wavelengths of spaceborne oceanic lidar for purposes of ocean detection at coastal and global scales are analyzed mainly in terms of the penetration depth. The global distribution of ocean penetration depth and the corresponding optimum wavelength bands are calculated by using the oceanic optical properties data from Moderate Resolution Imaging Spectroradiometer (MODIS). Ocean with optimum penetration wavelength of 488 nm covers 61.82% of the global ocean and the optimum wavelength of 443 nm with ocean area share of 14.81% is a good complement for 488 nm. The penetration depths of 96.26% of the global ocean are deeper than 0.8 times the euphotic zone depths by using wavelengths of 488 nm and 443 nm, simultaneously. More importantly, taking advantage of the characteristic of solar Fe Fraunhoferline (438.355 nm) and H-β Fraunhoferline (486.134 nm), 70% of the background light can be suppressed by a filter with bandwidth of 0.1 nm and the penetration depth can be increased by approximately 5.0%. In conclusion, we propose that 486.134 nm is the optimum wavelength of single-wavelength spaceborne oceanic lidar and the combination of 486.134 nm and 438.355 nm is a good choice for dual-wavelength lidar for purpose of global ocean detection.

Optimum wavelength of spaceborne oceanic lidar in penetration depth

A wavefront retrieval method for the quadriwave lateral shearing interferogram obtained by randomly encoded hybrid grating (REHG) is proposed. The REHG consists of a binary amplitude grating and a phase chessboard, and the Faunhofer diffractions of this grating only contain the ±1 orders in two orthogonal directions. As a result, no order selection mask is ever needed by the REHG for quadriwave lateral shearing interference. To retrieve the phase distributions from the REHG interferograms, fast Fourier transform (FFT) technique is employed at first to get the frequency spectrum. By performing inverse fast Fourier transform (IFFT) of the +1 order spectrum in the x and y directions, it is possible to extract shearing wavefronts from the interferogram in both two orthogonal directions. Using the translation property of Fourier transform, the relationship between the Fourier spectrum of the shearing wavefronts and the Fourier spectrum of the wavefront under test is deduced. The wavefront under test is retrieved by establishing an evaluation function firstly and finding the minimum value with least-square-solution. Analysis and compensations are made to reduce the errors in the testing results. Simulation experiments have shown that this method can retrieve different phase distributions without losing high-frequency information.

Retrieval of phase distributions from the quadriwave lateral shearing interferogram obtained by randomly encoded hybrid grating

Ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) (001) and (Mn,Sn) doped-PZT (PMSZT) (001) thin films have been integrated to high Tc superconducting c-oriented YBa2Cu3O7-x (YBCO) films for use as infrared detectors. The films were grown on LaAlO3(100) substrates by the pulsed laser deposition technique. The photocurrent responses of the PZT/YBCO and PMSZT/YBCO heterostructures fabricated as infrared (IR) detector have been measured from room temperature up to the ferroelectric phase transition temperatures. A stable photocurrent was observed to increase with increasing temperature throughout the temperature range. It was observed that the photocurrent of PMSZT/YBCO IR detector was significantly higher than that of the PZT/YBCO IR detectors in the temperature range of 20 - 170 degree(s)C. The current enhancement with temperature was found to be strongly polarization dependent and is due to the change of the pyroelectric coefficient of the PZT and PMSZT thin films with temperature. The YBCO thin films in the heterostructure were not used for their superconducting properties, but for their IR reflector-conductive electrode properties and as an atomic template for PZT/PMSZT epitaxial growth. With the high dielectric constants of PZT (600 - 800) and PMSZT (300 - 450) measured in this work, and the stable photocurrent in the infrared region (above 1 micrometers ), the PZT/YBCO and PMSZT/YBCO heterostructures are believed to be suitable materials for use in infrared detectors applicable at temperatures higher than room temperature.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Infrared photocurrent study of PZT/YBCO and PMSZT/YBCO heterostructures

The invention discloses a burning optimal method for power station boiler based on infrared radiant energy signal and the device It is divided into hardware and software The hardware comprises three parts The first part comprises near infrared radiant energy sensor installed on four corners of boiler The near infrared radiant energy is transferred to photoelectric transition component by fibers The photoelectric transition component is connected with the data collecting and transferring control module of lower computer The second part comprises the data collecting and transferring control module of lower computer located in the boiler body The third part comprises data analyzing and control signal outputting module of upper computer located in electric room The software system is developed by Labview programming software The near infrared radiant energy sensor is used to obtain intensity information of radiant energy in boiler and by the optimization method of artificial neutral network deviation value of radiant energy can be obtained Then the deviation value treated by filter is transferred to the control module of DCS boiler fuel to improve coal-feeding control logic and unit response speed for loading The running stability of steamer is insured

Power boiler burning optimization method and device based on infra red radiation energy signal

A model-based phase-shifting interferometer (MPI) is developed, in which a novel calculation technique is proposed instead of the traditional complicated system structure, to achieve versatile, high precision and quantitative surface tests. In the MPI, the partial null lens (PNL) is employed to implement the non-null test. With some alternative PNLs, similar as the transmission spheres in ZYGO interferometers, the MPI provides a flexible test for general spherical and aspherical surfaces. Based on modern computer modeling technique, a reverse iterative optimizing construction (ROR) method is employed for the retrace error correction of non-null test, as well as figure error reconstruction. A self-compiled ray-tracing program is set up for the accurate system modeling and reverse ray tracing. The surface figure error then can be easily extracted from the wavefront data in forms of Zernike polynomials by the ROR method. Experiments of the spherical and aspherical tests are presented to validate the flexibility and accuracy. The test results are compared with those of Zygo interferometer (null tests), which demonstrates the high accuracy of the MPI. With such accuracy and flexibility, the MPI would possess large potential in modern optical shop testing.

Dong Liu

Papers

Optimum wavelength of spaceborne oceanic lidar in penetration depth

Retrieval of phase distributions from the quadriwave lateral shearing interferogram obtained by randomly encoded hybrid grating

Infrared photocurrent study of PZT/YBCO and PMSZT/YBCO heterostructures

Power boiler burning optimization method and device based on infra red radiation energy signal

Model-based phase-shifting interferometer