Pub Date : 2019-12-02DOI: 10.1393/ncr/i2019-10166-0
P. Blasi
More than a century ago it was discovered that the Earth is bombarded by a penetrating radiation of cosmic origin, whose flux was later found to be dominated by charged particles. The discovery of cosmic rays led to many questions about their origin and about the way that they reach us from large distances. Here I will summarize some recent developments in our understanding of the acceleration mechanisms that energize a small number of thermal particles to highly non-thermal energies, with special attention on diffusive acceleration at supernova remnant shocks.
{"title":"Acceleration of galactic cosmic rays","authors":"P. Blasi","doi":"10.1393/ncr/i2019-10166-0","DOIUrl":"https://doi.org/10.1393/ncr/i2019-10166-0","url":null,"abstract":"More than a century ago it was discovered that the Earth is bombarded by a penetrating radiation of cosmic origin, whose flux was later found to be dominated by charged particles. The discovery of cosmic rays led to many questions about their origin and about the way that they reach us from large distances. Here I will summarize some recent developments in our understanding of the acceleration mechanisms that energize a small number of thermal particles to highly non-thermal energies, with special attention on diffusive acceleration at supernova remnant shocks.","PeriodicalId":501364,"journal":{"name":"La Rivista del Nuovo Cimento","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138521293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-11-05DOI: 10.1393/ncr/i2019-10165-1
Francesco Sciortino
Colloidal systems show beautiful examples of how entropy can lead to self-assembly of ordered structures, challenging our perception of disorder. In fact, dispersion of hard colloidal particles, systems in which by default entropy is the only thermodynamic driving force, displays both translational and orientational order on increasing density. Entropy is also a fundamental concept for describing effective interactions between colloidal particles. In several cases, entropy maximization generates strong attractive forces, capable of inducing condensation and sometimes crystallization. These entropic forces can even be exploited to drive colloids in specific locations or to orient them in the build-up of supracolloidal aggregates. Depletion interactions and combinatorial contributions are two important manifestations of these forces. Entropy also plays a leading role in systems exploring the bottom of their potential energy surface. In patchy colloids, particles interacting with highly anisotropic and localized potentials, ground-state structures are often degenerate in energy, leaving entropy to decide the thermodynamically stable polymorph. A striking result is the possibility of generating colloidal “liquids” thermodynamically more stable than colloidal “crystals” even at vanishing temperature.
{"title":"Entropy in self-assembly","authors":"Francesco Sciortino","doi":"10.1393/ncr/i2019-10165-1","DOIUrl":"https://doi.org/10.1393/ncr/i2019-10165-1","url":null,"abstract":"Colloidal systems show beautiful examples of how entropy can lead to self-assembly of ordered structures, challenging our perception of disorder. In fact, dispersion of hard colloidal particles, systems in which by default entropy is the only thermodynamic driving force, displays both translational and orientational order on increasing density. Entropy is also a fundamental concept for describing effective interactions between colloidal particles. In several cases, entropy maximization generates strong attractive forces, capable of inducing condensation and sometimes crystallization. These entropic forces can even be exploited to drive colloids in specific locations or to orient them in the build-up of supracolloidal aggregates. Depletion interactions and combinatorial contributions are two important manifestations of these forces. Entropy also plays a leading role in systems exploring the bottom of their potential energy surface. In patchy colloids, particles interacting with highly anisotropic and localized potentials, ground-state structures are often degenerate in energy, leaving entropy to decide the thermodynamically stable polymorph. A striking result is the possibility of generating colloidal “liquids” thermodynamically more stable than colloidal “crystals” even at vanishing temperature.","PeriodicalId":501364,"journal":{"name":"La Rivista del Nuovo Cimento","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138520954","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-10-14DOI: 10.1393/ncr/i2019-10164-2
Mariateresa Crosta
Astrometry is that fundamental part of astronomy which allows to determine the geometric, kinematical, and dynamical properties of celestial objects, including our own Galaxy, which is assembled and shaped by gravity. The knowledge of star positions was already important at the times of Hipparchus (190–120 BC) and his predecessors, Timocharis and Aristillos. Their cataloging (approximately 150 years earlier) of star positions enabled Hipparchus to update the observations with a precision of nearly half a degree and thus to discover the phenomenon of equinox precession. Nowadays a big jump is mandatory: positions, motions, and distances exist in the realm of the Einstein Theory and null geodesics represent our unique physical links to the stars through a curved space-time, namely a varying background geometry. Astrometry must be equipped with all of the proper tools of General Relativity to define the observables and the measurements needed for compiling astronomical catalogs at the microarcosecond accuracy and beyond. The astrometry of the 21st century, endowed with a fully relativistic framework, is fully fledged for new potential applications in astrophysics, can lead the way to forefront discoveries in fundamental physics, and is becoming the pillar of Local Cosmology. In this respect, it is more appropriate, in the 21st century, to refer to it as “Gravitational Astrometry”.
{"title":"Astrometry in the 21st century. From Hipparchus to Einstein","authors":"Mariateresa Crosta","doi":"10.1393/ncr/i2019-10164-2","DOIUrl":"https://doi.org/10.1393/ncr/i2019-10164-2","url":null,"abstract":"Astrometry is that fundamental part of astronomy which allows to determine the geometric, kinematical, and dynamical properties of celestial objects, including our own Galaxy, which is assembled and shaped by gravity. The knowledge of star positions was already important at the times of Hipparchus (190–120 BC) and his predecessors, Timocharis and Aristillos. Their cataloging (approximately 150 years earlier) of star positions enabled Hipparchus to update the observations with a precision of nearly half a degree and thus to discover the phenomenon of equinox precession. Nowadays a big jump is mandatory: positions, motions, and distances exist in the realm of the Einstein Theory and null geodesics represent our unique physical links to the stars through a curved space-time, namely a varying background geometry. Astrometry must be equipped with all of the proper tools of General Relativity to define the observables and the measurements needed for compiling astronomical catalogs at the microarcosecond accuracy and beyond. The astrometry of the 21st century, endowed with a fully relativistic framework, is fully fledged for new potential applications in astrophysics, can lead the way to forefront discoveries in fundamental physics, and is becoming the pillar of Local Cosmology. In this respect, it is more appropriate, in the 21st century, to refer to it as “Gravitational Astrometry”.","PeriodicalId":501364,"journal":{"name":"La Rivista del Nuovo Cimento","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138543014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-09-02DOI: 10.1393/ncr/i2019-10162-4
Yun-tai Chen, Yong Zhang, Li-sheng Xu
We present the theory and methods of earthquake rupture process inversion by using seismic and geodetic data, and their applications to scientific researches and earthquake emergency responses. It is shown that the knowledge obtained from these studies has much improved our understanding of the complexities of the earthquake source and causative mechanism of the earthquake disaster, and is of important reference value in earthquake disaster mitigation such as rapid earthquake emergency response. Especially since the 2008 Mw7.9 (MS8.0) Wenchuan, Sichuan, earthquake, fast and routine determination of the earthquake rupture process has been performed for significant earthquakes (MS ≥ 6.5 in China and MS ≥ 7.5 worldwide), and the results obtained are timely reported to the authorities and released to the public on the web site. The time consumed by the inversion has been reduced from more than 5 hours in 2009 to approximately 1–3 hours at present. The timely released rupture model was routinely used by the China Earthquake Administration and other authorities during the earthquake emergency responses period for destructive earthquakes, such as the 2010 Mw6.9 Yushu earthquake, the 2013 Mw6.6 Lushan earthquake, the 2014 Mw6.1 Ludian earthquake, and the 2015 Mw7.8 Gorkha, Nepal, earthquake, among the others.
{"title":"Inversion of earthquake rupture process: Theory and applications","authors":"Yun-tai Chen, Yong Zhang, Li-sheng Xu","doi":"10.1393/ncr/i2019-10162-4","DOIUrl":"https://doi.org/10.1393/ncr/i2019-10162-4","url":null,"abstract":"We present the theory and methods of earthquake rupture process inversion by using seismic and geodetic data, and their applications to scientific researches and earthquake emergency responses. It is shown that the knowledge obtained from these studies has much improved our understanding of the complexities of the earthquake source and causative mechanism of the earthquake disaster, and is of important reference value in earthquake disaster mitigation such as rapid earthquake emergency response. Especially since the 2008 <i>M</i><sub>w</sub>7.9 (<i>M</i><sub>S</sub>8.0) Wenchuan, Sichuan, earthquake, fast and routine determination of the earthquake rupture process has been performed for significant earthquakes (<i>M</i><sub>S</sub> ≥ 6.5 in China and <i>M</i><sub>S</sub> ≥ 7.5 worldwide), and the results obtained are timely reported to the authorities and released to the public on the web site. The time consumed by the inversion has been reduced from more than 5 hours in 2009 to approximately 1–3 hours at present. The timely released rupture model was routinely used by the China Earthquake Administration and other authorities during the earthquake emergency responses period for destructive earthquakes, such as the 2010 <i>M</i><sub>w</sub>6.9 Yushu earthquake, the 2013 <i>M</i><sub>w</sub>6.6 Lushan earthquake, the 2014 <i>M</i><sub>w</sub>6.1 Ludian earthquake, and the 2015 <i>M</i><sub>w</sub>7.8 Gorkha, Nepal, earthquake, among the others.","PeriodicalId":501364,"journal":{"name":"La Rivista del Nuovo Cimento","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138521291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-07-01DOI: 10.1393/ncr/i2019-10160-6
Terry Quinn
In my Commentary on the Metre Convention of 1875, modified by the second Convention in 1921, I examine its mission “to assure the international unification and perfection of the metric system” set out in the Preamble to the 1875 Convention and show how this continues to be its principal aim, with the metric system now being the International System of Units, SI. I examine the modern roles of the three organs of the Convention, the General Conference on Weights and Measures, the International Committee for Weights and Measures and the International Bureau of Weights and Measures—the permanent international scientific institute at Sevres. I discuss the interpretation of many of the key Articles of the Conventions, drawing upon decisions made by General Conferences. I discuss the recent interpretation of one of these by the International Committee. I draw attention to the 1960 draft of a proposed new Convention, much discussed at the 11th General Conference in 1960 but never adopted, which would have considerably eased recent financial difficulties by removing the requirement for unanimity in financial decisions. The new English edition of the Convention, in the Appendix, is the first complete and up to date English text to include both the Preamble to the 1875 Convention and the text of the second Convention of 1921.
{"title":"The Metre Convention of 1875: A Commentary and new English edition","authors":"Terry Quinn","doi":"10.1393/ncr/i2019-10160-6","DOIUrl":"https://doi.org/10.1393/ncr/i2019-10160-6","url":null,"abstract":"In my Commentary on the Metre Convention of 1875, modified by the second Convention in 1921, I examine its mission “to assure the international unification and perfection of the metric system” set out in the Preamble to the 1875 Convention and show how this continues to be its principal aim, with the metric system now being the International System of Units, SI. I examine the modern roles of the three organs of the Convention, the General Conference on Weights and Measures, the International Committee for Weights and Measures and the International Bureau of Weights and Measures—the permanent international scientific institute at Sevres. I discuss the interpretation of many of the key Articles of the Conventions, drawing upon decisions made by General Conferences. I discuss the recent interpretation of one of these by the International Committee. I draw attention to the 1960 draft of a proposed new Convention, much discussed at the 11th General Conference in 1960 but never adopted, which would have considerably eased recent financial difficulties by removing the requirement for unanimity in financial decisions. The new English edition of the Convention, in the Appendix, is the first complete and up to date English text to include both the Preamble to the 1875 Convention and the text of the second Convention of 1921.","PeriodicalId":501364,"journal":{"name":"La Rivista del Nuovo Cimento","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138521290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2019-06-27DOI: 10.1393/ncr/i2019-10159-y
E. Flamini, A. Adriani, J. W. Armstrong, F. Capaccioni, G. Filacchione, L. Iess, G. Mitri, S. Viviano
The Cassini-Huygens mission has characterized the Solar System exploration scenario for more than 30 years, from when it was conceived until the completion of its long life. Its legacy is an enormous amount of high quality scientific data and astonishing images of the Saturn system and its moons, Titan first. Also, the mission has been the gymnasium where new technologies and procedures have been discussed, developed and after adopted by many other missions. Cassini-Huygens also played a great role in allowing a new generation of scientists and engineers to increase their knowledge and skills, merging the already matured experience of a generation, formed on previous missions as Voyager, with a new generation belonging to many different countries. The international scenario that allowed the realization of the mission is the other distinguishing character of this adventure, led by the partnership of three space agencies, NASA with the Jet Propulsion Laboratory first, the European Space Agency-ESA for Huygens and the Italian Space Agency-ASI. This cooperative environment allowed both ESA and ASI to enter at best in the environment of the deep-space planetary missions and also provided the opportunity for other 15 nations to have their scientist on board and contributing to the mission. A cooperative effort, well guided and harmonized by the Project Science Group, lasted till the very end of the mission when the Cassini Grand Finale was played with the last plunge into the Saturn atmosphere. Hereafter, the mission is described including some details on the technical aspects of the Cassini spacecraft, the Huygens probe, the science instruments part of their payload and the science results are summarized with a special emphasis on the Italian contribution. This paper focuses on the science results in the cruise phase, where radio science experiments testing different aspects of relativistic gravity were performed. In particular, we describe the use of the novel Cassini radio system (based on Ka band frequencies, 32–34 GHz) to test the space components of the metric in the Solar System and a search of low-frequency gravitational waves, with a set of extensive observations in 2001 and 2002. The Cassini radio signal was tracked just prior to the final plunge into Saturn’s atmosphere (15 September 2017) from a new configuration of the Sardinia Radio Telescope called “Sardinia Deep Space Antenna”. The Venus and Jupiter fly-bys offered the opportunity to calibrate the VIMS instrument and to carry out new science observations.
{"title":"A unique mission: Cassini-Huygens, the Orbiter, the descent Probe and the cruise science","authors":"E. Flamini, A. Adriani, J. W. Armstrong, F. Capaccioni, G. Filacchione, L. Iess, G. Mitri, S. Viviano","doi":"10.1393/ncr/i2019-10159-y","DOIUrl":"https://doi.org/10.1393/ncr/i2019-10159-y","url":null,"abstract":"The Cassini-Huygens mission has characterized the Solar System exploration scenario for more than 30 years, from when it was conceived until the completion of its long life. Its legacy is an enormous amount of high quality scientific data and astonishing images of the Saturn system and its moons, Titan first. Also, the mission has been the gymnasium where new technologies and procedures have been discussed, developed and after adopted by many other missions. Cassini-Huygens also played a great role in allowing a new generation of scientists and engineers to increase their knowledge and skills, merging the already matured experience of a generation, formed on previous missions as Voyager, with a new generation belonging to many different countries. The international scenario that allowed the realization of the mission is the other distinguishing character of this adventure, led by the partnership of three space agencies, NASA with the Jet Propulsion Laboratory first, the European Space Agency-ESA for Huygens and the Italian Space Agency-ASI. This cooperative environment allowed both ESA and ASI to enter at best in the environment of the deep-space planetary missions and also provided the opportunity for other 15 nations to have their scientist on board and contributing to the mission. A cooperative effort, well guided and harmonized by the Project Science Group, lasted till the very end of the mission when the Cassini Grand Finale was played with the last plunge into the Saturn atmosphere. Hereafter, the mission is described including some details on the technical aspects of the Cassini spacecraft, the Huygens probe, the science instruments part of their payload and the science results are summarized with a special emphasis on the Italian contribution. This paper focuses on the science results in the cruise phase, where radio science experiments testing different aspects of relativistic gravity were performed. In particular, we describe the use of the novel Cassini radio system (based on <i>Ka</i> band frequencies, 32–34 GHz) to test the space components of the metric in the Solar System and a search of low-frequency gravitational waves, with a set of extensive observations in 2001 and 2002. The Cassini radio signal was tracked just prior to the final plunge into Saturn’s atmosphere (15 September 2017) from a new configuration of the Sardinia Radio Telescope called “Sardinia Deep Space Antenna”. The Venus and Jupiter fly-bys offered the opportunity to calibrate the VIMS instrument and to carry out new science observations.","PeriodicalId":501364,"journal":{"name":"La Rivista del Nuovo Cimento","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138521292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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