Search results for "dynamics."
showing 10 items of 9637 documents
Spatial correlations of vacuum fluctuations and the Casimir-Polder potential
2003
We calculate the Casimir-Polder intermolecular potential using an effective Hamiltonian recently introduced. We show that the potential can be expressed in terms of the dynamical polarizabilities of the two atoms and the equal-time spatial correlation of the electric field in the vacuum state. This gives support to an interesting physical model recently proposed in the literature, where the potential is obtained from the classical interaction between the instantaneous atomic dipoles induced and correlated by the vacuum fluctuations. Also, the results obtained suggest a more general validity of this intuitive model, for example when external boundaries or thermal fields are present.
Complete-active-space second-order perturbation theory (CASPT2//CASSCF) study of the dissociative electron attachment in canonical DNA nucleobases ca…
2015
Low-energy (0-3 eV) ballistic electrons originated during the irradiation of biological material can interact with DNA/RNA nucleobases yielding transient-anion species which undergo decompositions. Since the discovery that these reactions can eventually lead to strand breaking of the DNA chains, great efforts have been dedicated to their study. The main fragmentation at the 0-3 eV energy range is the ejection of a hydrogen atom from the specific nitrogen positions. In the present study, the methodological approach introduced in a previous work on uracil [I. González-Ramírez et al., J. Chem. Theory Comput. 8, 2769-2776 (2012)] is employed to study the DNA canonical nucleobases fragmentations…
Disentangling human from natural factors: Taphonomical value of microanatomical features on archaeological wood and charcoal assemblages
2020
International audience; Archaeobotanical charcoal and wood analyses rely on the observation of different macro and microanatomical features affecting wood structure to variable extents. These features may result from a wide range of intrinsic and extrinsic factors alluding to different stages of the wood's taphonomical history: initial growth conditions, human selection, transformation/use and discard, post-depositional processes and archaeological sampling strategies. Papers in this volume address taphonomy in this broad sense, through recent methodological work mainly based on experimentation and case studies from a variety of chrono-cultural and geographical contexts. The authors present…
Introducing a strategic perspective in lean thinking applications through system dynamics modelling: the dynamic Value Stream Map
2020
PurposeLean Thinking is an operation management discipline which aims to identify, map and analyse the activities forming a process to detect “value waste” and outline the most effective flow of activities to execute in sequence. Process mapping is often developed in lean projects through the use of the Value Stream Map (VSM). Like many other management tools, the VSM adopts a static and non-systemic perspective in the representation of an organizational process. This may result in the implementation of Lean projects inconsistent with the overall organizational long-term strategy, thus leading to dysfunctional performance. In order to overcome this limit, the paper suggests combining VSM wi…
Dynamic business modeling for sustainability: Exploring a system dynamics perspective to develop sustainable business models
2019
In the last decade, business models for sustainability have gained increasing attraction by corporate sustainability scholars with international conferences and scientific journals encouraging the development of the debate on their design, use and innovation processes. Capitalizing on the basic principles, requirements, and methodological limitations found in the literature on sustainability‐oriented business model design, this paper aims to conceptualize a dynamic business modeling for sustainability approach, which combines an adapted sustainable business model canvas and system dynamics modeling. To this end, the paper also illustrates the key operating principles of the proposed approac…
Innovation and Entrepreneurial Ecosystems: Structure, Boundaries, and Dynamics
2019
Recognizing the broader dimensions of entrepreneurial and innovation activities, holistic and inclusive networked approaches pave the way to co-creation activities that are essential for achieving sustainability in food systems. Recent studies have started to deepen what are the critical enablers for creating thriving entrepreneurial and innovation ecosystems. Networks that include firms, institutions, and several other relevant stakeholders in knowledge spillovers enable to produce more social and economic value through co-creation processes. However, due to the unique complexity within ecosystems, there is no standardized framework or strategy to develop entrepreneurial or innovation ecos…
Adsorbents and columns in analytical high-performance liquid chromatography: A perspective with regard to development and understanding
2012
A brief historical survey is presented on the evaluation of silica adsorbents in analytical HPLC. The theory of analytical HPLC is mostly still being based on the height equivalent to a theoretical plate concept and the van Deemter equation that was derived from gas phase adsorption involving a linear adsorption isotherm and fast mass transfer kinetics. One can obviously wonder whether the use of the van Deemter equation is relevant and valid for the evaluation of the performance of HPLC systems, where most often the liquid solutes involve charged molecules in electrolytes and in very many cases the adsorbates are macromolecules having diffusion coefficients of small magnitude. Instead of t…
Simultaneous optimization of mobile phase composition, column nature and length to analyse complex samples using serially coupled columns
2013
Abstract The combination of the selectivity of different columns serially coupled improves the separation expectancies with regard to the separation offered by each single column. In the reported approaches, either a pre-selected isocratic mobile phase composition or gradient program, giving rise to acceptable retention, is used. In previous work (JCA 1281 (2013) 94), we showed that the approach succeeds with conventional columns, assembled through zero-dead volume couplers. In this work, the simultaneous interpretive optimization of mobile phase composition and column nature and length, based on a limited number of experimental data, is demonstrated. This approach allows an impressive redu…
Prediction of Peak Shape and Characterization of Column Performance in Liquid Chromatography as a Function of Flow Rate
2015
Traditionally, column performance in liquid chromatography has been studied using information from the elution of probe compounds at different flow rates through van Deemter plots, which relate the column plate height to the linear mobile phase velocity. A more recent approach to characterize columns is the representation of the peak widths (or the right and left peak half-widths) for a set of compounds versus their retention times, which, for isocratic elution, give rise to almost linear plots. In previous work, these plots have been shown to facilitate the prediction of peak profiles (width and asymmetry) with optimization purposes. In this work, a detailed study on the dependence of the …
Phase coexistence in finite van der Waals systems
1999
Phase coexistence in finite systems obeying van der Waals equation of state is studied by minimizing a model free energy function for a spherical liquid droplet and a gaseous phase around it. Phase diagrams are calculated for finite systems with a large range of sizes. According to this model, the highest temperature where a droplet and vapour can exist in equilibrium decreases as N −0.4, where N is the number of particles in the system. The model predicts higher equilibrium vapour pressures than molecular dynamics simulations.