Author

# Claudio Zannoni

Other affiliations: University of Mons, European Laboratory for Non-Linear Spectroscopy, Université libre de Bruxelles ...read more

Bio: Claudio Zannoni is an academic researcher from University of Bologna. The author has contributed to research in topics: Liquid crystal & Monte Carlo method. The author has an hindex of 49, co-authored 313 publications receiving 8794 citations. Previous affiliations of Claudio Zannoni include University of Mons & European Laboratory for Non-Linear Spectroscopy.

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TL;DR: In this article, the authors developed a theory for an ensemble of such particles based on a general expansion of the pairwise intermolecular potential together with the molecular field approximation, and the dependence of the orientational properties of the uniaxial mesophase on the deviation from molecular cylindrical symmetry was calculated from the series expansion of pseudopotential.

Abstract: Most molecular theories of nematic liquid crystals assume that the constituent molecules are cylindrically symmetric. However, although this may be a useful approximation the molecules of real nematogens are of lower symmetry; here we develop a theory for an ensemble of such particles based on a general expansion of the pairwise intermolecular potential together with the molecular field approximation. The dependence of the orientational properties of the uniaxial mesophase on the deviation from molecular cylindrical symmetry is calculated from the series expansion of the pseudopotential. In these calculations the number of arbitrary parameters in the orientational pseudo-potential is reduced by assuming that the anisotropic intermolecular potential originates solely from dispersion forces. The theoretical predictions for the values of the ordering matrix and the entropy change at the nematic-isotropic transition are found to be in good agreement with those observed for 4,4′-dimethoxyazoxybenzene. In addit...

273 citations

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TL;DR: In this article, the authors introduce the concepts of order parameters and correlation functions needed for a description of orientational ordering in a liquid crystal or a membrane bilayer, and the theory of rotational depolarization of fluorescence for a probe in an ordered phase is introduced.

Abstract: The paper introduces in a systematic way the concepts of order parameters and correlation functions needed for a description of orientational ordering in a liquid crystal or a membrane bilayer. The strong collision and the diffusion model for reorientation are examined in some detail. After discussing the main characteristics of the very popular probes 1,6 diphenylhexatriene (DPH) and perylene the theory of rotational depolarization of fluorescence for a probe in an ordered phase is introduced. Time-dependent and steady state experiments in monodomains are discussed together with their angular dependence. Attention is then focussed on membrane vesicles. The theory for fluorescence depolarization is presented for probes with any orientation of the transition moments with a view to investigating the feasibility of using a certain probe to extract information on ordering and dynamics. Applications of the fluorescence depolarization technique to model and biological membranes are briefly reviewed. An appendix introducing irreducible tensors and Wigner rotation matrices properties is provided in order to keep the paper reasonably self-contained.

227 citations

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TL;DR: In this article, the Lebwohl-Lasher model of nematogens has been investigated using Monte Carlo simulations with periodic boundary conditions on a 30 × 30 × × 30 lattice.

Abstract: The Lebwohl-Lasher model of nematogens consists of a system of particles placed at the sites of a cubic lattice and interacting with a pair potential U i,j = -ϵ ij P 2(cos β ij ), where ϵ ij is a positive constant, ϵ, for nearest neighbours particles i and j and β ij is the angle between the axis of these two molecules. We have investigated this model using Monte Carlo simulations with periodic boundary conditions on a 30 × 30 × 30 lattice while the largest system previously studied was 20 × 20 × 20. The number of simulation runs near the transition is also significantly higher than in previous simulations to allow a more precise determination of the orientational transition temperature T * NI. The transition temperature has been placed at kT/ϵ = 1·1232 ± 0·0006, refining previous estimates. Orientational order parameters , have been calculated and a new algorithm is proposed for the computation of . Particular attention has been devoted to pretransitional properties. Pair correlations G 2...

207 citations

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TL;DR: In this paper, the authors provide a critical overview of the current computational techniques used to assess the morphology of organic:organic heterojunctions; they highlight the compromises that are necessary to handle large systems and multiple time scales while preserving the atomistic details required for subsequent computations of the electronic and optical properties.

Abstract: We report on the recent progress achieved in modeling the electronic processes that take place at interfaces between π-conjugated materials in organic opto-electronic devices. First, we provide a critical overview of the current computational techniques used to assess the morphology of organic:organic heterojunctions; we highlight the compromises that are necessary to handle large systems and multiple time scales while preserving the atomistic details required for subsequent computations of the electronic and optical properties. We then review some recent theoretical advances in describing the ground-state electronic structure at heterojunctions between donor and acceptor materials and highlight the role played by charge-transfer and long-range polarization effects. Finally, we discuss the modeling of the excited-state electronic structure at organic:organic interfaces, which is a key aspect in the understanding of the dynamics of photoinduced electron-transfer processes.

189 citations

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TL;DR: In this article, experimental evidence of a ferroelectric response to a switching electric field in a nematic liquid crystal is reported and connected with field-induced biaxiality, and it is concluded that the response is due to fieldinduced reorganization of polar cybotactic groups within the nematic phase.

Abstract: The still undiscoveredfluid ferroelectric nematic phase isexpected to exhibit a much faster and easier response to an external electric field compared to conventional ferroelectric smectic liquid crystals; therefore, the discovery of such a phase could open new avenues in electro-optic device technology. Here, experimental evidence of a ferroelectric response to a switching electric field inalowmolarmassnematicliquid crystalisreported andconnected with field-induced biaxiality. The fluid is made of bent-core polar molecules and is nematic over a range of 120-C. Combining repolarization current measurements, electro-optical characterizations, X-ray diffraction and computer simulations, ferroelectric switching is demonstrated and it is concluded that the response is due to field-induced reorganization of polar cybotactic groups within the nematic phase. This work represents significant progress toward the realization of ferroelectric fluids that can be aligned at command with a simple electric field.

183 citations

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01 May 1993

TL;DR: 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.

Abstract: 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.

29,323 citations

28 Jul 2005

TL;DR: PfPMP1）与感染红细胞、树突状组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�ly.

Abstract: 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。

18,940 citations

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TL;DR: This paper presents a meta-modelling procedure called "Continuum Methods within MD and MC Simulations 3072", which automates the very labor-intensive and therefore time-heavy and expensive process of integrating discrete and continuous components into a discrete-time model.

Abstract: 6.2.2. Definition of Effective Properties 3064 6.3. Response Properties to Magnetic Fields 3066 6.3.1. Nuclear Shielding 3066 6.3.2. Indirect Spin−Spin Coupling 3067 6.3.3. EPR Parameters 3068 6.4. Properties of Chiral Systems 3069 6.4.1. Electronic Circular Dichroism (ECD) 3069 6.4.2. Optical Rotation (OR) 3069 6.4.3. VCD and VROA 3070 7. Continuum and Discrete Models 3071 7.1. Continuum Methods within MD and MC Simulations 3072

13,286 citations

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TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

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TL;DR: Van Kampen as mentioned in this paper provides an extensive graduate-level introduction which is clear, cautious, interesting and readable, and could be expected to become an essential part of the library of every physical scientist concerned with problems involving fluctuations and stochastic processes.

Abstract: N G van Kampen 1981 Amsterdam: North-Holland xiv + 419 pp price Dfl 180 This is a book which, at a lower price, could be expected to become an essential part of the library of every physical scientist concerned with problems involving fluctuations and stochastic processes, as well as those who just enjoy a beautifully written book. It provides an extensive graduate-level introduction which is clear, cautious, interesting and readable.

3,647 citations