Atomic force algorithms in density functional theory electronic-structure techniques based on local orbitals

Electronic structure methods based on density-functional theory, pseudopotentials, and local-orbital basis sets offer a hierarchy of techniques for modeling complex condensed-matter systems with a wide range of precisions and computational speeds. We analyze the relationships between the algorithms for atomic forces in this hierarchy of techniques, going from empirical tight-binding through ab initio tight-binding to full ab initio. The analysis gives a unified overview of the force algorithms as applied within techniques based either on diagonalization or on linear-scaling approaches. The use of these force algorithms is illustrated by practical calculations with the CONQUEST code, in which different techniques in the hierarchy are applied in a concerted manner.     

Multiphoton multifocal microscopy exploiting a diffractive optical element

Multiphoton multifocal microscopy (MMM) usually has been achieved through a combination of galvo scanners with microlens arrays, with rotating disks of microlens arrays, and cascaded beam splitters with asynchronous rastering of scanning mirrors. Here we describe the achievement of a neat and compact MMM by use of a high-diffraction-efficiency diffractive-optic element that generates a multiple-spot grid of uniform intensity to achieve higher fidelity in imaging of live cells at adequate speeds.     

Midrapidity neutral-pion production in proton-proton collisions at square root s = 200 GeV

The invariant differential cross section for inclusive neutral-pion production in p+p collisions at sqrt[s]=200 GeV has been measured at midrapidity (|eta|<0.35) over the range 1相似文献   

Elliptic flow of identified hadrons in Au+Au collisions at sqrt sNN =200 GeV

The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at sqrt[s(NN)]=200 GeV for identified and inclusive charged particle production at central rapidities (|eta|<0.35) with respect to the reaction plane defined at high rapidities (|eta|=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.     

Scaling properties of proton and antiproton production in sqrt[s(NN)]=200 GeV Au+Au collisions

We report on the yield of protons and antiprotons, as a function of centrality and transverse momentum, in Au+Au collisions at sqrt[s(NN)]=200 GeV measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider. In central collisions at intermediate transverse momenta (1.5相似文献   

Synthetic studies toward nortriterpenoids of schisandraceae family. Approach to the construction of functionalized C/D and A/B ring units of micrandilactone C and rubrifloradilactone B

Construction of 6/7 fused bicycles featuring C/D rings of micrandilactone C and rubrifloradilactone B is reported through IMDA reaction of properly designed substrates. Also a route to the construction of a tricycle having A/B ring of nortriterpenoids of schisandra family is reported using RCM and a bromonium ion initiated cycloetherification reaction as the key steps.     

An iterative calculation to derive extinction-to-backscatter ratio based on lidar measurements

The aerosol optical thickness (AOT) is an important parameter for understanding the radiative impact of aerosols. AOT based on lidar measurements is often limited by its finite detection range. In this paper, we have reported a method of fitting and iterative calculation to derive the extinction profile of background aerosols from 0 to 30 km at 532 nm, which is virtually the AOT of the entire atmosphere. The mean extinction derived from this method at the ground level tallies with visibility measurement and it is also consistent with the sun-photometer data, within experimental error. These data have been further treated to study the dust cases. For most of the cases, transmission losses were determined to estimate the extinction as well as lidar ratio. The result of the analysis shows that for background aerosols, a mean lidar ratio of 47±15 sr was found. For dust layers, a mean lidar ratio of 44±19 sr and an optical thickness of 0.53±0.49 were determined at 532 nm.     

An optical study of phase transitions of poly (ethylene terephthalate-co-p-hydroxybenzoic acid) liquid crystal

The copolyester containing 40 mol % ethylene terephthalate (PET) and 60 mol % p-hydroxybenzoate (HB) units has been reported by several investigators to be biphasic in the solid and the liquid states. The reported thermal transitions in the two phases, however, are in part contradictory, perhaps partly due to different polymerization conditions. The present work is a study of the transitions in each of the two phases of this copolyester by polarized light microscopy and by light transmission measurements. By light transmission measurements, the two phases were found to have two different glass transition temperatures for the onset of segmental motion, consistent with two assignable temperatures (T.). Cold crystallization and melting in each of the two different phases was also detected. The results help clarify the nature of transitions and agree with the results of dynamic mechanical analysis on the same thermotropic liquid crystalline copolyester.