Claudio Della Volpe - Academia.edu (original) (raw)
Papers by Claudio Della Volpe
BioPhysical Economics and Resource Quality, 2018
The EROI is one of the most important indices to evaluate the net energy output of a source of pr... more The EROI is one of the most important indices to evaluate the net energy output of a source of primary energy (there is a lively debate on the usability of this kind of parameter, but here we will use it under the hypothesis that it is a good way to establish if an oil company has a level of efficiency close to other energetic sources). It is generally defined as the ratio between the energy extracted by a given resource and the energy costs sustained to extract that energy. We tried to set up an alternative method for the calculation of the EROI, taking (1) as a proxy of the energy costs the available data about the CO 2 emissions of the oil companies, as reported in the sustainability reports (SRs), recommended by the international organisms such as IPCC and WBCSD, although not mandatory, and (2) as a proxy of the energy extracted the CO 2 emissions estimate obtained by a stoichiometric conversion of the oil/gas production declared by the oil companies. Both proxies have been also corrected to take into account the different CO 2 emission rate per unit energy of oil and gas. The resulting estimates of EROI are rather homogeneous and not too different from the values reported in the literature. The method could be suitable for year-by-year comparison of the time evolution of this important energy quality parameter for the individual energyproducing and energy-delivering companies.
Langmuir : the ACS journal of surfaces and colloids, Jan 20, 2006
Journal of Colloid and Interface Science, 1997
the moment of glory for acid-base theories: the ''dominant This paper considers the correctness o... more the moment of glory for acid-base theories: the ''dominant This paper considers the correctness of the application of Goodparadigm'' (in terms of Kuhn's theory) is that solid surface van Oss theory (vOGT) to the calculation of acid-base compofree energy has many components, whose values can be nents of solid surface free energies. Theory equations are written calculated from thermodynamic or spectroscopic data. in a matrix form, and their application is analyzed particularly Acid-base theories have their basis in the splitting of from a mathematical point of view. A calculation procedure simisurface free energy g Tot into two components: lar to the approach used for other scales of acid-base strength is suggested to obtain in a straightforward manner the necessary material coefficients. The chemical consequences of these consider-g Tot Å g LW / g AB. [1] ations are also discussed. The acceptability of current experimental literature data and the validity of the calculations obtained from This equation is the achievement of many years of scienthem by the proposed method are considered, showing the origin tific work and asserts the idea that ''dispersive'' (LW or of some inconsistencies in current results. Some general considera-Lifschitz-van der Waals) and acid-base (AB) interactions regarding the difficulties commonly encountered in the applitions are independent. These terms are fully defined in cation of vOGT are also discussed, and it is shown that they many texts (2-5). can be rationalized or eliminated with more acid solvents being At least two different approaches exist to expressing in included in the solvent set and the properties of the reference greater detail the acid-base contribution: solvent being correctly chosen. The difficulties encountered in correctly expressing the acid properties of some polymers are closely • Fowkes (5) relates adhesion work (a free energy contriexamined. Finally, some indications are given of the future possible bution) and its trend with temperature (the entropic contribudevelopments of vOGT. ᭧ 1997 Academic Press tion) to enthalpic contributions calculated by Drago theory;
European Journal of Physics, 2011
The familiar Young contact angle measurement of a liquid at equilibrium on a solid is a fundament... more The familiar Young contact angle measurement of a liquid at equilibrium on a solid is a fundamental aspect of capillary phenomena. But in the real world it is not so easy to observe it. This is due to the roughness and/or heterogeneity of real surfaces, which typically are not perfectly planar and chemically homogeneous. What can be easily detected, and in a repeatable way, are advancing and receding contact angles. In this paper, we discuss a simple model which accounts for the onset of advancing and receding contact angles measured by the Wilhelmy microbalance, one of the most powerful techniques for contact angle measurements. The model also explains the experimental observation that advancing and receding contact angles become closer to each other when the system is gently 'shaken', by supplying mechanical energy in an appropriate way. The model may be pedagogically useful in introducing students and teachers to aspects of capillary phenomena which are not usually discussed in basic physics courses.
ABSTRACT The problem of error propagation in the estimate of material components for quadratic mu... more ABSTRACT The problem of error propagation in the estimate of material components for quadratic multicomponent surface free energy theories is addressed. It is shown that invariance properties of the model equations, through an appropriate group of linear transformations, imply a very peculiar structure of any merit function used for general best-fit estimates of surface free energy components in quadratic multicomponent models. Such a structure is reflected in the distribution of merit-function minima, involved in the calculation of best-fit estimates to surface free energy components, according to the nonlinear method. A simple and reasonable strategy allows to describe the displacement of minima due to uncertainties on experimental data, and therefore to evaluate the consequent error propagation on the final results.
Journal of Adhesion Science and Technology, 1994
Abstract: Two model systems (glass plates and polyimide films), modified on one face by different... more Abstract: Two model systems (glass plates and polyimide films), modified on one face by different techniques, have been analysed using a Cahn microbalance. The results show that if the sample immersion is vertical,(ie the effect of net horizontal component of surface ...
Journal of the Chemical Society, Faraday Transactions, 1993
Enthalpies of dilution of ternary aqueous solutions containing biuret or urea and positional isom... more Enthalpies of dilution of ternary aqueous solutions containing biuret or urea and positional isomers of alkan-m-ols have been determined by flow microcalorimetry at 298.15 K. Pairwise cross-interaction coefficients of the virial expansion of the excess enthalpies were evaluated. The values of the coefficients are positive, depending in a very complex manner on the length of the alkyl chain and on the position occupied by the hydroxy group along the alkyl chain. The behaviour of these systems seems to be determined by a balance between favourable hydrophilic–hydrophilic and repulsive hydrophilic–hydrophobic interactions. When the hydroxy group occupies more central positions, unfavourable interactions prevail and the cross coefficient for the alkanol bearing the longest alkyl chain is almost zero.
Molecular Plant-Microbe Interactions, 1999
Pseudomonas syringae pv. syringae produces two groups of cyclic lipodepsipeptides (LDPs): the non... more Pseudomonas syringae pv. syringae produces two groups of cyclic lipodepsipeptides (LDPs): the nona-peptides syringomycins, syringostatins, and syringotoxin (ST), and the more complex syringopeptins composed of either 22 or 25 amino acid residues (SP22 and SP25). Both classes of peptides significantly contribute to bacterial pathogenesis and their primary target of action seems to be the plasma membrane. We studied and compared the activity of some members of these two classes of LDPs on red blood cells and on model membranes (monolayers and unilamellar vesicles). All peptides induced red blood cell hemolysis. The mechanism was apparently that of a colloid-osmotic shock caused by the formation of pores, as it could be prevented by osmoticants of adequate size. Application of the Renkin equation indicated a radius of approximately 1 nm for the lesions formed by syringopeptins SP22A and SP25A, whereas those formed by syringomycin E (SRE) had a variable, dose-dependent size ranging from...
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004
The advancing angle is the commonest way to measure and use the contact angle. Sometimes its use ... more The advancing angle is the commonest way to measure and use the contact angle. Sometimes its use is an acceptable approximation, whereas in other cases it is simply not useful or misleading. This is the case of a natural porous material, such as stone. The stone materials are heterogeneous and rough, and the application of protective agents makes their surfaces even more complex. This paper confirms that the measurement of the advancing angles can only indicate the presence of the protective, not its effective protecting ability. On the contrary, the receding angles correlate better with the chemical structure and protective ability of the protecting agents (e.g. with the water absorption). Some examples of evaluations of commercial and newly synthesised protective polymers show the advantages and limitations of the use of the contact angles and the difficulties of their interpretation. Moreover, new and originally chosen protective agents, i.e. some cationic surfactants already used as "rinsing aids" and polyvynilpyrrolidone waxes, have been tested as protective with interesting results. The time dependence of protection efficacy and its correlation with contact angle have also been tested.
Polystyrene Petri dishes, aminated by a plasma deposition process, were surface modified by the c... more Polystyrene Petri dishes, aminated by a plasma deposition process, were surface modified by the covalent linking of two different enzymatically modified hairy regions (HRs) from pectin containing, for example, rhamnogalacturonan-I and xylogalacturonan structural elements. The two polysaccharide preparations share the same structural elements of apple pectin, but the relative amounts and lengths of the neutral side chains present differ. Surface analysis by X-ray photoelectron spectroscopy, contact angle measurement, and atomic force microscope (AFM) force-separation curves was used to characterize the effects on surface chemistry and interfacial forces of the surface modification process. Cell adhesion experiments using continuous L-929 fibroblasts and primary aortic smooth muscle cells were performed to evaluate the effect of the polysaccharide nature on cell adhesion. Results show that immobilization of the HR affects the interfacial field of forces and the cell behavior: “equilib...
videos of notched stick rotating at different speed and frequency taken at higher resolution (Son... more videos of notched stick rotating at different speed and frequency taken at higher resolution (Sony RX100 IV) as well as simulations at 156Hz or nonrotating ; the .mpg files are simulations, while the MP4 files are experimental files<br>
arXiv: Theoretical Economics, 2020
The behavior of complex systems is one of the most intriguing phenomena investigated by recent sc... more The behavior of complex systems is one of the most intriguing phenomena investigated by recent science; natural and artificial systems offer a wide opportunity for this kind of analysis. The energy conversion is both a process based on important physical laws and one of the most important economic sectors; the interaction between these two aspects of energy production suggests the possibility to apply some of the approaches of the dynamic systems' analysis. In particular, a phase plot, which is one of the methods to detect a correlation between quantities in a complex system, provides a good way to establish qualitative analogies between the ecological systems and the economic ones and may shed light on the processes governing the evolution of the system. The aim of this paper is to highlight the analogies between some peculiar characteristics of the oil production vs. price and show in which way such characteristics are similar to some behavioral mechanisms found in Nature.
arXiv: General Finance, 2017
A phase plot of the oil economy is built using the literature data of world oil production, price... more A phase plot of the oil economy is built using the literature data of world oil production, price, and EROEI (Energy Returned on Energy Invested). An analogy between the oil economy and the Benard convection is proposed; some methods of interpretation and forecast of the system behavior are also shown based on "phase portrait" using as main variables the price, production and EROEI values. A scenery is proposed on this basis.
Surface Innovations
A brief history of the Wilhelmy technique for surface tension and contact angle measurements intr... more A brief history of the Wilhelmy technique for surface tension and contact angle measurements introduces the equation and the methods necessary to apply this modern and automatic procedure correctly. Many simple practices may avoid systematic errors and allow reliable results to be obtained for both quantities. The paper analyzes not only simple runs – that is, applications to standard shapes such as cylinders and parallelepipeds, rigid, non-porous samples immersed in probe liquids of low viscosity – but also non-simple runs – that is, applications to non-standard samples such as disk-shaped samples, porous and flexible samples, planar samples with different contact angles on their two opposite faces, and to the case of more viscous fluids. Many experimental details such as the size ratio of specimens to the liquid container may be extremely important; their role and the history of discussion about these topics are reviewed and discussed herein. Also, the possible determination of co...
PLOS ONE
An intriguing simple toy, commonly known as the Notched Stick, is discussed as an example of a "v... more An intriguing simple toy, commonly known as the Notched Stick, is discussed as an example of a "vibrot", a device designed and built to yield conversion of mechanical vibrations into a rotational motion. The toy, that can be briefly described as a propeller fixed on a stick by means of a nail and free to rotate around it, is investigated from both an experimental and a numerical point of view, under various conditions and settings, to investigate the basic working principles of the device. The conversion efficiency from vibration to rotational motion turns out to be very small, or even not detectable at all, whenever the propeller is tightly connected to the stick nail and perfectly axisymmetrical with respect to the nail axis; the small effects possibly observed can be ascribed to friction forces. In contrast, the device succeeds in converting vibrations into rotations when the propeller center of mass is not aligned with the nail axis, a condition occurring when either the nail-propeller coupling is not tight or the propeller is not completely axisymmetrical relative to the nail axis. The propeller rotation may be induced by a process of parametric resonance for purely vertical oscillations of the nail, by ordinary resonance if the nail only oscillates horizontally or, finally, by a combination of both processes when nail oscillations take place in an intermediate direction. Parametric resonance explains the onset of rotations also when the weight of the propeller is negligible. In contrast with what is commonly claimed in the literature, the possible elliptical motion of the nail, due to a composition of two harmonic motions of the same frequency imposed along orthogonal directions, seems unnecessary to determine the propeller rotation.
Surface Innovations
Much interest has recently been focused on contact angles, wetting and non-wettable surfaces as i... more Much interest has recently been focused on contact angles, wetting and non-wettable surfaces as is evidenced by the rapid pace and sheer number of papers published in recent years. However, in many cases there exist misconceptions and misuses of terminology, leading to misinterpretation of experimental contact angles, measurements of which deceptively appear to be simple. Terms describing contact angles, wettability, superhydrophobicity and similar other terminology are loosely used. In this contribution, key terms used in relation to contact angles are defined precisely based on the accumulative knowledge from the surface chemistry community over the last decades. The definitions provided are scientifically rigorous to avoid any ambiguity and confusion. The theoretical considerations underlying these definitions are only briefly mentioned, with references to the relevant papers. Interpretation and meaning of the measured contact angles can be made simpler if the basic concepts are ...
In this study, the results of different analyses carried out on thirteen samples of figulina pott... more In this study, the results of different analyses carried out on thirteen samples of figulina pottery are presented. These samples are from four Italian Neolithic sites and are dated to the end of the 6th --beginning of the 5th millennium BC cal. On the basis of the results obtained from scanning electron microscopy, energy dispersive X ray spectroscopy, porosimetry, density measurements and X ray diffractometry, specific features of this ceramics have been inferred. These features can be as preliminary, even in view of the limited number of the analysed specimens, indicators to tell locally produced from imported products. Moreover, interesting data on porosity and related microstructure and phase composition emerged from the experimental results. In particular, an elevated concentration of glassy phase has been found in all samples, although in the prehistoric sites no indications or remains of any advanced pyrotechnological facility were found. The estimated firing temperatures in...
Journal of the Chemical Society, Faraday Transactions, 1992
Abstract Excess enthalpies of ternary aqueous solutions containing different alkane-m, n-diols ha... more Abstract Excess enthalpies of ternary aqueous solutions containing different alkane-m, n-diols have been determined at 298.15 K. The enthalpic interaction coefficients obtained were interpreted according to an interaction model which includes the presence of a ...
BioPhysical Economics and Resource Quality, 2018
The EROI is one of the most important indices to evaluate the net energy output of a source of pr... more The EROI is one of the most important indices to evaluate the net energy output of a source of primary energy (there is a lively debate on the usability of this kind of parameter, but here we will use it under the hypothesis that it is a good way to establish if an oil company has a level of efficiency close to other energetic sources). It is generally defined as the ratio between the energy extracted by a given resource and the energy costs sustained to extract that energy. We tried to set up an alternative method for the calculation of the EROI, taking (1) as a proxy of the energy costs the available data about the CO 2 emissions of the oil companies, as reported in the sustainability reports (SRs), recommended by the international organisms such as IPCC and WBCSD, although not mandatory, and (2) as a proxy of the energy extracted the CO 2 emissions estimate obtained by a stoichiometric conversion of the oil/gas production declared by the oil companies. Both proxies have been also corrected to take into account the different CO 2 emission rate per unit energy of oil and gas. The resulting estimates of EROI are rather homogeneous and not too different from the values reported in the literature. The method could be suitable for year-by-year comparison of the time evolution of this important energy quality parameter for the individual energyproducing and energy-delivering companies.
Langmuir : the ACS journal of surfaces and colloids, Jan 20, 2006
Journal of Colloid and Interface Science, 1997
the moment of glory for acid-base theories: the ''dominant This paper considers the correctness o... more the moment of glory for acid-base theories: the ''dominant This paper considers the correctness of the application of Goodparadigm'' (in terms of Kuhn's theory) is that solid surface van Oss theory (vOGT) to the calculation of acid-base compofree energy has many components, whose values can be nents of solid surface free energies. Theory equations are written calculated from thermodynamic or spectroscopic data. in a matrix form, and their application is analyzed particularly Acid-base theories have their basis in the splitting of from a mathematical point of view. A calculation procedure simisurface free energy g Tot into two components: lar to the approach used for other scales of acid-base strength is suggested to obtain in a straightforward manner the necessary material coefficients. The chemical consequences of these consider-g Tot Å g LW / g AB. [1] ations are also discussed. The acceptability of current experimental literature data and the validity of the calculations obtained from This equation is the achievement of many years of scienthem by the proposed method are considered, showing the origin tific work and asserts the idea that ''dispersive'' (LW or of some inconsistencies in current results. Some general considera-Lifschitz-van der Waals) and acid-base (AB) interactions regarding the difficulties commonly encountered in the applitions are independent. These terms are fully defined in cation of vOGT are also discussed, and it is shown that they many texts (2-5). can be rationalized or eliminated with more acid solvents being At least two different approaches exist to expressing in included in the solvent set and the properties of the reference greater detail the acid-base contribution: solvent being correctly chosen. The difficulties encountered in correctly expressing the acid properties of some polymers are closely • Fowkes (5) relates adhesion work (a free energy contriexamined. Finally, some indications are given of the future possible bution) and its trend with temperature (the entropic contribudevelopments of vOGT. ᭧ 1997 Academic Press tion) to enthalpic contributions calculated by Drago theory;
European Journal of Physics, 2011
The familiar Young contact angle measurement of a liquid at equilibrium on a solid is a fundament... more The familiar Young contact angle measurement of a liquid at equilibrium on a solid is a fundamental aspect of capillary phenomena. But in the real world it is not so easy to observe it. This is due to the roughness and/or heterogeneity of real surfaces, which typically are not perfectly planar and chemically homogeneous. What can be easily detected, and in a repeatable way, are advancing and receding contact angles. In this paper, we discuss a simple model which accounts for the onset of advancing and receding contact angles measured by the Wilhelmy microbalance, one of the most powerful techniques for contact angle measurements. The model also explains the experimental observation that advancing and receding contact angles become closer to each other when the system is gently 'shaken', by supplying mechanical energy in an appropriate way. The model may be pedagogically useful in introducing students and teachers to aspects of capillary phenomena which are not usually discussed in basic physics courses.
ABSTRACT The problem of error propagation in the estimate of material components for quadratic mu... more ABSTRACT The problem of error propagation in the estimate of material components for quadratic multicomponent surface free energy theories is addressed. It is shown that invariance properties of the model equations, through an appropriate group of linear transformations, imply a very peculiar structure of any merit function used for general best-fit estimates of surface free energy components in quadratic multicomponent models. Such a structure is reflected in the distribution of merit-function minima, involved in the calculation of best-fit estimates to surface free energy components, according to the nonlinear method. A simple and reasonable strategy allows to describe the displacement of minima due to uncertainties on experimental data, and therefore to evaluate the consequent error propagation on the final results.
Journal of Adhesion Science and Technology, 1994
Abstract: Two model systems (glass plates and polyimide films), modified on one face by different... more Abstract: Two model systems (glass plates and polyimide films), modified on one face by different techniques, have been analysed using a Cahn microbalance. The results show that if the sample immersion is vertical,(ie the effect of net horizontal component of surface ...
Journal of the Chemical Society, Faraday Transactions, 1993
Enthalpies of dilution of ternary aqueous solutions containing biuret or urea and positional isom... more Enthalpies of dilution of ternary aqueous solutions containing biuret or urea and positional isomers of alkan-m-ols have been determined by flow microcalorimetry at 298.15 K. Pairwise cross-interaction coefficients of the virial expansion of the excess enthalpies were evaluated. The values of the coefficients are positive, depending in a very complex manner on the length of the alkyl chain and on the position occupied by the hydroxy group along the alkyl chain. The behaviour of these systems seems to be determined by a balance between favourable hydrophilic–hydrophilic and repulsive hydrophilic–hydrophobic interactions. When the hydroxy group occupies more central positions, unfavourable interactions prevail and the cross coefficient for the alkanol bearing the longest alkyl chain is almost zero.
Molecular Plant-Microbe Interactions, 1999
Pseudomonas syringae pv. syringae produces two groups of cyclic lipodepsipeptides (LDPs): the non... more Pseudomonas syringae pv. syringae produces two groups of cyclic lipodepsipeptides (LDPs): the nona-peptides syringomycins, syringostatins, and syringotoxin (ST), and the more complex syringopeptins composed of either 22 or 25 amino acid residues (SP22 and SP25). Both classes of peptides significantly contribute to bacterial pathogenesis and their primary target of action seems to be the plasma membrane. We studied and compared the activity of some members of these two classes of LDPs on red blood cells and on model membranes (monolayers and unilamellar vesicles). All peptides induced red blood cell hemolysis. The mechanism was apparently that of a colloid-osmotic shock caused by the formation of pores, as it could be prevented by osmoticants of adequate size. Application of the Renkin equation indicated a radius of approximately 1 nm for the lesions formed by syringopeptins SP22A and SP25A, whereas those formed by syringomycin E (SRE) had a variable, dose-dependent size ranging from...
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004
The advancing angle is the commonest way to measure and use the contact angle. Sometimes its use ... more The advancing angle is the commonest way to measure and use the contact angle. Sometimes its use is an acceptable approximation, whereas in other cases it is simply not useful or misleading. This is the case of a natural porous material, such as stone. The stone materials are heterogeneous and rough, and the application of protective agents makes their surfaces even more complex. This paper confirms that the measurement of the advancing angles can only indicate the presence of the protective, not its effective protecting ability. On the contrary, the receding angles correlate better with the chemical structure and protective ability of the protecting agents (e.g. with the water absorption). Some examples of evaluations of commercial and newly synthesised protective polymers show the advantages and limitations of the use of the contact angles and the difficulties of their interpretation. Moreover, new and originally chosen protective agents, i.e. some cationic surfactants already used as "rinsing aids" and polyvynilpyrrolidone waxes, have been tested as protective with interesting results. The time dependence of protection efficacy and its correlation with contact angle have also been tested.
Polystyrene Petri dishes, aminated by a plasma deposition process, were surface modified by the c... more Polystyrene Petri dishes, aminated by a plasma deposition process, were surface modified by the covalent linking of two different enzymatically modified hairy regions (HRs) from pectin containing, for example, rhamnogalacturonan-I and xylogalacturonan structural elements. The two polysaccharide preparations share the same structural elements of apple pectin, but the relative amounts and lengths of the neutral side chains present differ. Surface analysis by X-ray photoelectron spectroscopy, contact angle measurement, and atomic force microscope (AFM) force-separation curves was used to characterize the effects on surface chemistry and interfacial forces of the surface modification process. Cell adhesion experiments using continuous L-929 fibroblasts and primary aortic smooth muscle cells were performed to evaluate the effect of the polysaccharide nature on cell adhesion. Results show that immobilization of the HR affects the interfacial field of forces and the cell behavior: “equilib...
videos of notched stick rotating at different speed and frequency taken at higher resolution (Son... more videos of notched stick rotating at different speed and frequency taken at higher resolution (Sony RX100 IV) as well as simulations at 156Hz or nonrotating ; the .mpg files are simulations, while the MP4 files are experimental files<br>
arXiv: Theoretical Economics, 2020
The behavior of complex systems is one of the most intriguing phenomena investigated by recent sc... more The behavior of complex systems is one of the most intriguing phenomena investigated by recent science; natural and artificial systems offer a wide opportunity for this kind of analysis. The energy conversion is both a process based on important physical laws and one of the most important economic sectors; the interaction between these two aspects of energy production suggests the possibility to apply some of the approaches of the dynamic systems' analysis. In particular, a phase plot, which is one of the methods to detect a correlation between quantities in a complex system, provides a good way to establish qualitative analogies between the ecological systems and the economic ones and may shed light on the processes governing the evolution of the system. The aim of this paper is to highlight the analogies between some peculiar characteristics of the oil production vs. price and show in which way such characteristics are similar to some behavioral mechanisms found in Nature.
arXiv: General Finance, 2017
A phase plot of the oil economy is built using the literature data of world oil production, price... more A phase plot of the oil economy is built using the literature data of world oil production, price, and EROEI (Energy Returned on Energy Invested). An analogy between the oil economy and the Benard convection is proposed; some methods of interpretation and forecast of the system behavior are also shown based on "phase portrait" using as main variables the price, production and EROEI values. A scenery is proposed on this basis.
Surface Innovations
A brief history of the Wilhelmy technique for surface tension and contact angle measurements intr... more A brief history of the Wilhelmy technique for surface tension and contact angle measurements introduces the equation and the methods necessary to apply this modern and automatic procedure correctly. Many simple practices may avoid systematic errors and allow reliable results to be obtained for both quantities. The paper analyzes not only simple runs – that is, applications to standard shapes such as cylinders and parallelepipeds, rigid, non-porous samples immersed in probe liquids of low viscosity – but also non-simple runs – that is, applications to non-standard samples such as disk-shaped samples, porous and flexible samples, planar samples with different contact angles on their two opposite faces, and to the case of more viscous fluids. Many experimental details such as the size ratio of specimens to the liquid container may be extremely important; their role and the history of discussion about these topics are reviewed and discussed herein. Also, the possible determination of co...
PLOS ONE
An intriguing simple toy, commonly known as the Notched Stick, is discussed as an example of a "v... more An intriguing simple toy, commonly known as the Notched Stick, is discussed as an example of a "vibrot", a device designed and built to yield conversion of mechanical vibrations into a rotational motion. The toy, that can be briefly described as a propeller fixed on a stick by means of a nail and free to rotate around it, is investigated from both an experimental and a numerical point of view, under various conditions and settings, to investigate the basic working principles of the device. The conversion efficiency from vibration to rotational motion turns out to be very small, or even not detectable at all, whenever the propeller is tightly connected to the stick nail and perfectly axisymmetrical with respect to the nail axis; the small effects possibly observed can be ascribed to friction forces. In contrast, the device succeeds in converting vibrations into rotations when the propeller center of mass is not aligned with the nail axis, a condition occurring when either the nail-propeller coupling is not tight or the propeller is not completely axisymmetrical relative to the nail axis. The propeller rotation may be induced by a process of parametric resonance for purely vertical oscillations of the nail, by ordinary resonance if the nail only oscillates horizontally or, finally, by a combination of both processes when nail oscillations take place in an intermediate direction. Parametric resonance explains the onset of rotations also when the weight of the propeller is negligible. In contrast with what is commonly claimed in the literature, the possible elliptical motion of the nail, due to a composition of two harmonic motions of the same frequency imposed along orthogonal directions, seems unnecessary to determine the propeller rotation.
Surface Innovations
Much interest has recently been focused on contact angles, wetting and non-wettable surfaces as i... more Much interest has recently been focused on contact angles, wetting and non-wettable surfaces as is evidenced by the rapid pace and sheer number of papers published in recent years. However, in many cases there exist misconceptions and misuses of terminology, leading to misinterpretation of experimental contact angles, measurements of which deceptively appear to be simple. Terms describing contact angles, wettability, superhydrophobicity and similar other terminology are loosely used. In this contribution, key terms used in relation to contact angles are defined precisely based on the accumulative knowledge from the surface chemistry community over the last decades. The definitions provided are scientifically rigorous to avoid any ambiguity and confusion. The theoretical considerations underlying these definitions are only briefly mentioned, with references to the relevant papers. Interpretation and meaning of the measured contact angles can be made simpler if the basic concepts are ...
In this study, the results of different analyses carried out on thirteen samples of figulina pott... more In this study, the results of different analyses carried out on thirteen samples of figulina pottery are presented. These samples are from four Italian Neolithic sites and are dated to the end of the 6th --beginning of the 5th millennium BC cal. On the basis of the results obtained from scanning electron microscopy, energy dispersive X ray spectroscopy, porosimetry, density measurements and X ray diffractometry, specific features of this ceramics have been inferred. These features can be as preliminary, even in view of the limited number of the analysed specimens, indicators to tell locally produced from imported products. Moreover, interesting data on porosity and related microstructure and phase composition emerged from the experimental results. In particular, an elevated concentration of glassy phase has been found in all samples, although in the prehistoric sites no indications or remains of any advanced pyrotechnological facility were found. The estimated firing temperatures in...
Journal of the Chemical Society, Faraday Transactions, 1992
Abstract Excess enthalpies of ternary aqueous solutions containing different alkane-m, n-diols ha... more Abstract Excess enthalpies of ternary aqueous solutions containing different alkane-m, n-diols have been determined at 298.15 K. The enthalpic interaction coefficients obtained were interpreted according to an interaction model which includes the presence of a ...