Orientational and induced contributions to the depolarized Rayleigh spectra of liquid and supercooled ortho-terphenyl

The depolarized light scattering spectra of the glass forming liquid ortho-terphenyl have been calculated in the low frequency region using molecular dynamics simulation. Realistic system's configurations are produced by using a recent flexible molecular model and combined with two limiting polarizability schemes, both of them using the dipole-induced-dipole contributions at first and second order. The calculated Raman spectral shape are in good agreement with the experimental results in a large temperature range. The analysis of the different contributions to the Raman spectra emphasizes that the orientational and the collision-induced (translational) terms lie on the same time-scale and are of comparable intensity. Moreover, the cross terms are always found to be an important contribution to the scattering intensity.Comment: RevTeX4, 7 pages, 8 eps figure

Dynamic force spectroscopy of DNA hairpins. II. Irreversibility and dissipation

We investigate irreversibility and dissipation in single molecules that cooperatively fold/unfold in a two state manner under the action of mechanical force. We apply path thermodynamics to derive analytical expressions for the average dissipated work and the average hopping number in two state systems. It is shown how these quantities only depend on two parameters that characterize the folding/unfolding kinetics of the molecule: the fragility and the coexistence hopping rate. The latter has to be rescaled to take into account the appropriate experimental setup. Finally we carry out pulling experiments with optical tweezers in a specifically designed DNA hairpin that shows two-state cooperative folding. We then use these experimental results to validate our theoretical predictions.Comment: 28 pages, 12 figure

Molecular dynamics simulation study of the high frequency sound waves in the fragile glass former ortho-terphenyl

Using a realistic flexible molecule model of the fragile glass former orthoterphenyl, we calculate via molecular dynamics simulation the collective dynamic structure factor, recently measured in this system by Inelastic X-ray Scattering. The comparison of the simulated and measured dynamic structure factor, and the study of its properties in an extended momentum, frequency and temperature range allows: i) to conclude that the utilized molecular model gives rise to a dynamic structure factor in agreement with the experimental data, for those thermodynamic states and momentum values where the latter are available; ii) to confirm the existence of a slope discontinuity on the T-dependence of the sound velocity that, at finite Q, takes place at a temperature T_x higher than the calorimetric glass transition temperature T_g; iii) to find that the values of T_x is Q-dependent and that its vanishing Q limit is consistent with T_g. The latter finding is interpreted within the framework of the current description of the dynamics of supercooled liquids in terms of exploration of the potential energy landscape.Comment: RevTex, 9 pages, 10 eps figure

Applied research by design: an experimental collaborative and interdisciplinary design charrette

This article reports on one experimental case of interdisciplinary collaboration on a design and planning exercise across several scales – local through urban to regional – and sectors – private, public, scholarly, and interest groups. The case is a collaborative and interdisciplinary design charrette on sustainable urbanism for envisioning the future of the Greater Metropolitan Area of Florence in Italy. The experiment entailed the attempt to integrate complex urban conditions via the design charrette in order to create more healthy and sustainable cities. This collaborative work shows how conditions that are at times not addressed comprehensively nor holistically can be combined through doing applied research by design; where design is understood as a process of discovery and creation that results in synthesis. The article details the methodology applied, and provides an initial assessment on the process that the charrette employed. Moreover, it highlights some professional and policy implications of the effort. Finally, it provides a provisional assessment on learning outcomes and addresses opportunities to improve future exercises of this nature

Symplectic geometry of Cartan–Hartogs domains

This paper studies the geometry of Cartan–Hartogs domains from the symplectic point of view. Inspired by duality between compact and noncompact Hermitian symmetric spaces, we construct a dual counterpart of Cartan–Hartogs domains and give explicit expression of global Darboux coordinates for both Cartan–Hartogs domains and their dual. Further, we compute their symplectic capacity and show that a Cartan–Hartogs domain admits a symplectic duality if and only if it reduces to be a complex hyperbolic space

Studio dell’insediamento protostorico in un’area della Sardegna centro-occidentale tramite strumenti GIS ed analisi multivariate

The authors analyze, as a sample-area, the region that includes the municipality of Mogoro, in central-western Sardinia, with the objective to reconstruct, through the study of the settlements and their relationships, some economic and social aspects of the human groups of nuragic culture that inhabited this area between the 18th and the 8th century BC. The territory is located at the foot of Monte Arci, along the Mogoro river that runs through the southern part of the plain of the Campidano of Oristano. The area has been intensively investigated from the half of the past century; an in-depth stratigraphic investigation was carried out since 1994 near the nuragic site of Cuccurada, the main center of an articulated territorial system including a rich network of monuments related to the nuragic civilization. The results are illustrated through various research methods: GIS, with the application of spatial analysis tools, and multivariate analysis (cluster and principal components analysis) that allowed to set out new hypotheses on occupation and populating dynamics and to identify among pre-historical monuments one or more homogeneous and distinguishable groups, resulting from a database in which geomorphological characteristics are recorded. A hierarchical organization and a specific criterion for exploiting and monitoring the landscape have been developed, in which settlement choices depend on functionality criteria, having nuraghi and villages a key role on the strategic control of the territor

Effective temperature of active matter

We follow the dynamics of an ensemble of interacting self-propelled motorized particles in contact with an equilibrated thermal bath. We find that the fluctuation-dissipation relation allows for the definition of an effective temperature that is compatible with the results obtained using a tracer particle as a thermometer. The effective temperature takes a value which is higher than the temperature of the bath and it is continuously controlled by the motor intensity

Kovacs effects in an aging molecular liquid

We study by means of molecular dynamics simulations the aging behavior of a molecular model of ortho-terphenyl. We find evidence of a a non-monotonic evolution of the volume during an isothermal-isobaric equilibration process, a phenomenon known in polymeric systems as Kovacs effect. We characterize this phenomenology in terms of landscape properties, providing evidence that, far from equilibrium, the system explores region of the potential energy landscape distinct from the one explored in thermal equilibrium. We discuss the relevance of our findings for the present understanding of the thermodynamics of the glass state.Comment: RevTeX 4, 4 pages, 5 eps figure