We present a greatly simplified model (a ‘toy model’) for the rheological behavior of gases in la... more We present a greatly simplified model (a ‘toy model’) for the rheological behavior of gases in laminar motion, whose viscosity arises mainly from thermal diffusion of momentum among layers. The model is based on the usual mesoscopic representation of a fluid in laminar motion (i.e. many layers reciprocally sliding on each other), where the mechanical coupling among layers is modeled by means of mass exchange, that in turns results in momentum diffusion transversally to the fluid flow. In particular, the model is based on the conceptual analogy between: a laminarly flowing fluid, on one side, and, on the other side, an arbitrary number of identical trains sliding on parallel rails, reciprocally interacting through mass exchange between nearest neighbors. Before presenting the complete model, a simplest case is considered, in order to familiarize learners with the idea that mass exchange between two mechanical systems can give rise to an emerging interaction force between them. The pr...
... Two series of measurements have been car-ried out corresponding, respectively, to like poles ... more ... Two series of measurements have been car-ried out corresponding, respectively, to like poles or unlike poles facing through the sphere. ... J. Phys. 71 9437 A Bonanno, G Bozzo, M Camarca and P Sapia1 Department of Physics, University of Calabria, Italy ...
Foucault dissipation in a rolling cylinder: a webcam quantitative study
European Journal of Physics, 2011
ABSTRACT In this paper we present an experimental strategy to measure the micro power dissipation... more ABSTRACT In this paper we present an experimental strategy to measure the micro power dissipation due to Foucault 'eddy' currents in a copper cylinder rolling on two parallel conductive rails in the presence of a magnetic field. Foucault power dissipation is obtained from kinematical measurements carried out by using a common PC webcam and video analysis done by means of software tools freely available within Windows operating system (Paint and Movie Maker). The proposed method allows us to experimentally discern the contribution to dissipation due to the velocity-independent rolling friction from that owed to the viscous-like friction emerging from complex electrodynamic interactions among eddy currents and the external magnetic field. In this way a microdissipation of some tens of µW is measured. The easily reproducible experimental setup, the simple implementation of data analysis and the discussion on various experimental approaches and strategies make the proposed activity highly significant for university undergraduates, since involved crucial skills can be efficiently strengthened.
The effects of salinity on the lateral headgroup interactions of dipalmitoylphosphatidylcholine (... more The effects of salinity on the lateral headgroup interactions of dipalmitoylphosphatidylcholine (DPPC) molecules in fully hydrated multilayers have been investigated by spin label electron spin resonance (ESR) spectroscopy and differential scanning calorimetry (DSC). By increasing the NaC1 concentration from 0 to 3 M in the multilayers' dispersion medium, the ESR measurements performed with the 5-stearic acid spin label and di-tert-butyl-nitroxide show an increase in the orientational degree of order of the lipid molecules, mainly in the gel phase, and a decrease of the membrane permeability. An upward shift from 31.5 ~ to 36.5 ~ and from 40.5 ~ to 41.9 ~ of the pre-and main DPPC phase transition temperatures, respectively, is observed with 5-SASL, while slightly higher values are detected with DTBN. Small effects are evident on the properties of the liquid crystalline phase of the DPPC multilayers. The DSC measurements also reveal an upward shift of the pre-and main transition temperatures. The shifts, however, are more marked if compared to the ones observed with the ESR technique. The findings suggest an increase in the packing density of the DPPC molecules in the multilayers in presence of high salt concentration. Dehydration of the DPPC interfacial region with a variation of the lateral electrostatic interactions between phospholipid polar heads trigger the phenomena observed.
Infrared vision of artworks based on web cameras: a cross-disciplinary laboratory of optics
Journal of Physics: Conference Series, 2019
Applied optics offers a way to teach fundamental concepts of light properties and radiation-matte... more Applied optics offers a way to teach fundamental concepts of light properties and radiation-matter interaction through interdisciplinary experimental activities. In this framework, we designed a cross-disciplinary laboratorial activity on optics applied to artworks based on DIY instrumentation for the secondary school level. The teaching sequence includes inquiry-based seminars and laboratorial activities on imaging, spectrometry, infrared applications to conservation science.
We present a greatly simplified model (a ‘toy model’) for the rheological behavior of gases in la... more We present a greatly simplified model (a ‘toy model’) for the rheological behavior of gases in laminar motion, whose viscosity arises mainly from thermal diffusion of momentum among layers. The model is based on the usual mesoscopic representation of a fluid in laminar motion (i.e. many layers reciprocally sliding on each other), where the mechanical coupling among layers is modeled by means of mass exchange, that in turns results in momentum diffusion transversally to the fluid flow. In particular, the model is based on the conceptual analogy between: a laminarly flowing fluid, on one side, and, on the other side, an arbitrary number of identical trains sliding on parallel rails, reciprocally interacting through mass exchange between nearest neighbors. Before presenting the complete model, a simplest case is considered, in order to familiarize learners with the idea that mass exchange between two mechanical systems can give rise to an emerging interaction force between them. The pr...
... Two series of measurements have been car-ried out corresponding, respectively, to like poles ... more ... Two series of measurements have been car-ried out corresponding, respectively, to like poles or unlike poles facing through the sphere. ... J. Phys. 71 9437 A Bonanno, G Bozzo, M Camarca and P Sapia1 Department of Physics, University of Calabria, Italy ...
Foucault dissipation in a rolling cylinder: a webcam quantitative study
European Journal of Physics, 2011
ABSTRACT In this paper we present an experimental strategy to measure the micro power dissipation... more ABSTRACT In this paper we present an experimental strategy to measure the micro power dissipation due to Foucault 'eddy' currents in a copper cylinder rolling on two parallel conductive rails in the presence of a magnetic field. Foucault power dissipation is obtained from kinematical measurements carried out by using a common PC webcam and video analysis done by means of software tools freely available within Windows operating system (Paint and Movie Maker). The proposed method allows us to experimentally discern the contribution to dissipation due to the velocity-independent rolling friction from that owed to the viscous-like friction emerging from complex electrodynamic interactions among eddy currents and the external magnetic field. In this way a microdissipation of some tens of µW is measured. The easily reproducible experimental setup, the simple implementation of data analysis and the discussion on various experimental approaches and strategies make the proposed activity highly significant for university undergraduates, since involved crucial skills can be efficiently strengthened.
The effects of salinity on the lateral headgroup interactions of dipalmitoylphosphatidylcholine (... more The effects of salinity on the lateral headgroup interactions of dipalmitoylphosphatidylcholine (DPPC) molecules in fully hydrated multilayers have been investigated by spin label electron spin resonance (ESR) spectroscopy and differential scanning calorimetry (DSC). By increasing the NaC1 concentration from 0 to 3 M in the multilayers' dispersion medium, the ESR measurements performed with the 5-stearic acid spin label and di-tert-butyl-nitroxide show an increase in the orientational degree of order of the lipid molecules, mainly in the gel phase, and a decrease of the membrane permeability. An upward shift from 31.5 ~ to 36.5 ~ and from 40.5 ~ to 41.9 ~ of the pre-and main DPPC phase transition temperatures, respectively, is observed with 5-SASL, while slightly higher values are detected with DTBN. Small effects are evident on the properties of the liquid crystalline phase of the DPPC multilayers. The DSC measurements also reveal an upward shift of the pre-and main transition temperatures. The shifts, however, are more marked if compared to the ones observed with the ESR technique. The findings suggest an increase in the packing density of the DPPC molecules in the multilayers in presence of high salt concentration. Dehydration of the DPPC interfacial region with a variation of the lateral electrostatic interactions between phospholipid polar heads trigger the phenomena observed.
Infrared vision of artworks based on web cameras: a cross-disciplinary laboratory of optics
Journal of Physics: Conference Series, 2019
Applied optics offers a way to teach fundamental concepts of light properties and radiation-matte... more Applied optics offers a way to teach fundamental concepts of light properties and radiation-matter interaction through interdisciplinary experimental activities. In this framework, we designed a cross-disciplinary laboratorial activity on optics applied to artworks based on DIY instrumentation for the secondary school level. The teaching sequence includes inquiry-based seminars and laboratorial activities on imaging, spectrometry, infrared applications to conservation science.
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