David Jacob - Academia.edu (original) (raw)
Papers by David Jacob
2005 International Symposium on Computational Intelligence in Robotics and Automation
Classical Reinforcement Learning is a general leaming paradigm with wide applicability in many pr... more Classical Reinforcement Learning is a general leaming paradigm with wide applicability in many problem domains. Where embodied agents are concerned, however, it is unable to take advantage of the structured, regular nature of the physical world to maximise learning efficiency. Here, using a model of a three joint robot arm, we show initial learning accelerated by an order of magnitude using simple constraints to produce characteristic attitudes, implemented as part of the learning algorithm. We point up possible parallels with constraints on the movement of natural organisms owing to their detailed mechanical structure. The work forms part of our EMBER framework for reinforcement learning in embodied agents introduced in [2] and developed in [3].
In some Christian churches there exists a tension between the resurrection of the body and a cult... more In some Christian churches there exists a tension between the resurrection of the body and a cultural view of an immaterial heaven as the endpoint of eternal life. This MAP examines this tension and shows the biblical teaching of the resurrection from the dead in a bodily form on this present perfected earth as the endpoint of eternal life for the Christian. A multi-part Bible study was written to teach believers the understanding of resurrection as taught in the Bible. Eight volunteer participants from Rock Island Arsenal and Risen Christ Lutheran Church, Davenport, Iowa were asked five interview questions before and after the Bible study. The results of the data gathered and discussed and the conclusion from this study shows there is misunderstanding among believers on resurrection theology. There is also room for improved understanding of the biblical resurrection teaching.
Zentralblatt für Chirurgie - Zeitschrift für Allgemeine, Viszeral-, Thorax- und Gefäßchirurgie, 2019
Zusammenfassung Einleitung Die Medikation des chirurgischen Intensivpatienten ist schwer kalkulie... more Zusammenfassung Einleitung Die Medikation des chirurgischen Intensivpatienten ist schwer kalkulierbar durch gestörte Organfunktionen, Organversagen, pathophysiologische Veränderungen bei schwerer Erkrankung und in der Sepsis, laufende Organersatz-, Nierenersatz- und Leberersatzverfahren sowie die unterschiedliche Pharmakokinetik/Pharmakodynamik (PK/PD) von medikamentösen Substanzen und zahlreichen Medikamenteninteraktionen. Ziel Interdisziplinäres Vorgehen im klinischen Alltag zur Optimierung sowohl der Vielfachmedikation als auch der laufenden medikamentösen Therapie von Patienten vor indizierten Operationen oder Interventionen sowie im Rahmen des peri- und postoperativen intensivmedizinischen Managements. Methode Etablierung einer „Drug Interaction Stewardship“ (DIS), analog und zeitgleich zur bereits etablierten Antibiotic Stewardship (ABS) in der Routine einer chirurgischen Intensivstation. Erweiterung des etablierten therapeutischen Drug-Monitorings (TDM) auf Standard-Antiinfek...
Physical Review B, 2015
We investigate the orbital origin of the Fano-Kondo line shapes measured in STM spectroscopy of m... more We investigate the orbital origin of the Fano-Kondo line shapes measured in STM spectroscopy of magnetic adatoms on metal substrates. To this end we calculate the low-bias tunnel spectra of a Co adatom on the (001) and (111) Cu surfaces with our density functional theory-based ab initio transport scheme augmented by local correlations. In order to associate different d-orbitals with different Fano line shapes we only correlate individual 3d-orbitals instead of the full Co 3d-shell. We find that Kondo peaks arising in different d-levels indeed give rise to different Fano features in the conductance spectra. Hence the shape of measured Fano features allows us to draw some conclusions about the orbital responsible for the Kondo resonance, although the actual shape is also influenced by temperature, effective interaction and charge fluctuations. Comparison with a simplified model shows that line shapes are mostly the result of interference between tunneling paths through the correlated d-orbital and the sp-type orbitals on the Co atom. Very importantly, the amplitudes of the Fano features vary strongly among orbitals, with the 3z 2-orbital featuring by far the largest amplitude due to its strong direct coupling to the s-type conduction electrons.
Http Www Theses Fr, 2012
1 : étude expérimentale avec des atomes de sodium dans un piège optique Soutenue le 25 mai 2012 d... more 1 : étude expérimentale avec des atomes de sodium dans un piège optique Soutenue le 25 mai 2012 devant le jury composé de :
Journal De Physique I, 1994
The polarisation robustness of vectorial lasers with respect to différent kinds of perturbation i... more The polarisation robustness of vectorial lasers with respect to différent kinds of perturbation is theoretically investigated in thé framework of a Landau potential approach. It is shown that usual internat and external perturbations may be classified in two main classes uniform perturbations which alter thé two eigenstates in thé same manner, and differential perturbations that favor one eigenstate with respect
When a magnetic molecule is deposited on a metallic substrate or attached to metallic contacts it... more When a magnetic molecule is deposited on a metallic substrate or attached to metallic contacts its magnetic moment may actually be screened by the conduction electrons due to the Kondo effect. In view of possible applications of molecular magnets such as nanoscale spintronics and magnetic storage devices, it is important to being able to predict whether the Kondo effect will take place or not in a given system. Also one would like to understand in detail how the Kondo effect emerges in a given situation and how it is controlled by the various parameters such as the molecular conformation and the type of substrate. Using a recently developed ab initio approach for molecular devices [1,2] that explicitly takes into account the strong electronic correlations that give rise to the Kondo effect, we have calculated the electronic structure and transport properties of different magnetic molecules coupled to nanocontacts [3] and surfaces [4]. Our calculations shed light on the complex nature of the Kondo effect in molecular-scale devices. [1] D.
Physical Review B, 2006
Contrary to the antiferromagnetic and insulating character of bulk NiO, one-dimensional chains of... more Contrary to the antiferromagnetic and insulating character of bulk NiO, one-dimensional chains of this material can become half-metallic due to the lower coordination of their atoms. Here we present ab initio electronic structure and quantum transport calculations of ideal infinitely long NiO chains and of more realistic short ones suspended between Ni electrodes. While infinite chains are insulating, short suspended chains are half-metallic minority-spin conductors which display very large magnetoresistance and a spin-valve behaviour controlled by a single atom.
Journal de Radiologie, 2007
Ultrasound guided interventional radiology
Physical Review Letters, 2009
We study the impact of dynamical correlations on the electronic structure and coherent transport ... more We study the impact of dynamical correlations on the electronic structure and coherent transport properties of Cu nanocontacts hosting a single magnetic impurity (Ni,Co,Fe) in the contact region. The strong dynamical correlations of the impurity 3d-electrons are fully taken into account by combining density functional calculations with a dynamical treatment of the impurity 3d-shell in the one-crossing approximation. We find that dynamical correlations give rise to the Kondo effect and lead to Fano features in the coherent transport characteristics similar to those observed in related experiments.
Physical Review B, 2006
We show how to extract the orbital contribution to the transport eigenchannels from a firstprinci... more We show how to extract the orbital contribution to the transport eigenchannels from a firstprinciples quantum transport calculation in a nanoscopic conductor. This is achieved by calculating and diagonalizing the first-principles transmission matrix reduced to selected scattering crosssections. As an example, the orbital nature of the eigenchannels in the case of Ni nanocontacts is explored, stressing the difficulties inherent to the use of non-orthogonal basis sets
Physical Review B, 2010
We present an approach for calculating the electronic structure and transport properties of nanos... more We present an approach for calculating the electronic structure and transport properties of nanoscopic conductors that takes into account the dynamical correlations of strongly interacting d-or f-electrons by combining density functional theory calculations with the dynamical mean-field theory. While the density functional calculation yields a static mean-field description of the weakly interacting electrons, the dynamical mean-field theory explicitly takes into account the dynamical correlations of the strongly interacting d-or f-electrons of transition metal atoms. As an example we calculate the electronic structure and conductance of Ni nanocontacts between Cu electrodes. We find that the dynamical correlations of the Ni 3d-electrons give rise to quasi-particle resonances at the Fermi-level in the spectral density. The quasi-particle resonances in turn lead to Fano lineshapes in the conductance characteristics of the nanocontacts similar to those measured in recent experiments of magnetic nanocontacts.
Physical Review B, 2004
ABSTRACT Charge localization seems unlikely to occur in two vertically coupled symmetric quantum ... more ABSTRACT Charge localization seems unlikely to occur in two vertically coupled symmetric quantum dots even if a small bias voltage breaks the exact isospin-symmetry of the system. However for a three-electron double quantum dot we find a strong localization of charges at certain vertically applied magnetic fields. The charge localization is directly connected to new ground state transitions between eigenstates differing only in parity. The transitions are driven by magnetic field dependent Coulomb correlations between the electrons and give rise to strong isospin blockade signatures in transport through the double dot system.
Physical Review A, 2012
We study experimentally the equilibrium phase diagram of a spin 1 Bose-Einstein condensate with a... more We study experimentally the equilibrium phase diagram of a spin 1 Bose-Einstein condensate with antiferromagnetic interactions, in a regime where spin and spatial degrees of freedom are decoupled. For a given total magnetization mz, we observe for low magnetic fields an "antiferromagnetic" phase where atoms condense in the m = ±1 Zeeman states, and occupation of the m = 0 state is suppressed. Conversely, for large enough magnetic fields, a phase transition to a "broken axisymmetry" phase takes place: The m = 0 component becomes populated and rises sharply above a critical field Bc(mz). This behavior results from the competition between antiferromagnetic spin-dependent interactions (dominant at low fields) and the quadratic Zeeman energy (dominant at large fields). We compare the measured Bc as well as the global shape of the phase diagram with mean-field theory, and find good quantitative agreement.
Optics Letters, 1995
The high sensitivity of the eigenstates of a large-finesse passive Fabry-Perot cavity is used to ... more The high sensitivity of the eigenstates of a large-finesse passive Fabry-Perot cavity is used to measure the residual anisotropy of supermirrors at strictly normal incidence. An experimental demonstration leads to the measurement of phase retardances of the order of 10 26 rad.
Nature Nanotechnology, 2013
The properties of quantum systems interacting with their environment, commonly called open quantu... more The properties of quantum systems interacting with their environment, commonly called open quantum systems, can be strongly affected by this interaction. While this can lead to unwanted consequences, such as causing decoherence in qubits used for quantum computation 1 , it can also be exploited as a probe of the environment. For example, magnetic resonance imaging is based on the dependence of the spin relaxation times of protons 2 in water molecules in a host's tissue 3. Here we show that the excitation energy of a single spin, which is determined by magnetocrystalline anisotropy and controls its stability and suitability for use in magnetic data storage devices 4 , can be modified by varying the exchange coupling of the spin to a nearby conductive electrode. Using scanning tunnelling microscopy and spectroscopy, we observe variations up to a factor of two of the spin excitation energies of individual atoms as the strength of the spin's coupling to the surrounding electronic bath changes. These observations, combined with calculations, show that exchange coupling can strongly modify the magnetic anisotropy. This system is thus one of the few open quantum systems in which the energy levels, and not just the excited-state lifetimes, can be controllably
Nature, 2009
Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk, electronic conduction in th... more Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk, electronic conduction in these materials takes place mainly through the s and p electrons, whereas the magnetic moments are mostly in the narrow d-electron bands, where they tend to align. This general picture may change at the nanoscale because electrons at the surfaces of materials experience interactions that differ from those in the bulk. Here we show direct evidence for such changes: electronic transport in atomic-scale contacts of pure ferromagnets (iron, cobalt and nickel), despite their strong bulk ferromagnetism, unexpectedly reveal Kondo physics, that is, the screening of local magnetic moments by the conduction electrons below a characteristic temperature 1. The Kondo effect creates a sharp resonance at the Fermi energy, affecting the electrical properties of the system;this appears as a Fano-Kondo resonance 2 in the conductance characteristics as observed in other artificial nanostructures 3,
2005 International Symposium on Computational Intelligence in Robotics and Automation
Classical Reinforcement Learning is a general leaming paradigm with wide applicability in many pr... more Classical Reinforcement Learning is a general leaming paradigm with wide applicability in many problem domains. Where embodied agents are concerned, however, it is unable to take advantage of the structured, regular nature of the physical world to maximise learning efficiency. Here, using a model of a three joint robot arm, we show initial learning accelerated by an order of magnitude using simple constraints to produce characteristic attitudes, implemented as part of the learning algorithm. We point up possible parallels with constraints on the movement of natural organisms owing to their detailed mechanical structure. The work forms part of our EMBER framework for reinforcement learning in embodied agents introduced in [2] and developed in [3].
In some Christian churches there exists a tension between the resurrection of the body and a cult... more In some Christian churches there exists a tension between the resurrection of the body and a cultural view of an immaterial heaven as the endpoint of eternal life. This MAP examines this tension and shows the biblical teaching of the resurrection from the dead in a bodily form on this present perfected earth as the endpoint of eternal life for the Christian. A multi-part Bible study was written to teach believers the understanding of resurrection as taught in the Bible. Eight volunteer participants from Rock Island Arsenal and Risen Christ Lutheran Church, Davenport, Iowa were asked five interview questions before and after the Bible study. The results of the data gathered and discussed and the conclusion from this study shows there is misunderstanding among believers on resurrection theology. There is also room for improved understanding of the biblical resurrection teaching.
Zentralblatt für Chirurgie - Zeitschrift für Allgemeine, Viszeral-, Thorax- und Gefäßchirurgie, 2019
Zusammenfassung Einleitung Die Medikation des chirurgischen Intensivpatienten ist schwer kalkulie... more Zusammenfassung Einleitung Die Medikation des chirurgischen Intensivpatienten ist schwer kalkulierbar durch gestörte Organfunktionen, Organversagen, pathophysiologische Veränderungen bei schwerer Erkrankung und in der Sepsis, laufende Organersatz-, Nierenersatz- und Leberersatzverfahren sowie die unterschiedliche Pharmakokinetik/Pharmakodynamik (PK/PD) von medikamentösen Substanzen und zahlreichen Medikamenteninteraktionen. Ziel Interdisziplinäres Vorgehen im klinischen Alltag zur Optimierung sowohl der Vielfachmedikation als auch der laufenden medikamentösen Therapie von Patienten vor indizierten Operationen oder Interventionen sowie im Rahmen des peri- und postoperativen intensivmedizinischen Managements. Methode Etablierung einer „Drug Interaction Stewardship“ (DIS), analog und zeitgleich zur bereits etablierten Antibiotic Stewardship (ABS) in der Routine einer chirurgischen Intensivstation. Erweiterung des etablierten therapeutischen Drug-Monitorings (TDM) auf Standard-Antiinfek...
Physical Review B, 2015
We investigate the orbital origin of the Fano-Kondo line shapes measured in STM spectroscopy of m... more We investigate the orbital origin of the Fano-Kondo line shapes measured in STM spectroscopy of magnetic adatoms on metal substrates. To this end we calculate the low-bias tunnel spectra of a Co adatom on the (001) and (111) Cu surfaces with our density functional theory-based ab initio transport scheme augmented by local correlations. In order to associate different d-orbitals with different Fano line shapes we only correlate individual 3d-orbitals instead of the full Co 3d-shell. We find that Kondo peaks arising in different d-levels indeed give rise to different Fano features in the conductance spectra. Hence the shape of measured Fano features allows us to draw some conclusions about the orbital responsible for the Kondo resonance, although the actual shape is also influenced by temperature, effective interaction and charge fluctuations. Comparison with a simplified model shows that line shapes are mostly the result of interference between tunneling paths through the correlated d-orbital and the sp-type orbitals on the Co atom. Very importantly, the amplitudes of the Fano features vary strongly among orbitals, with the 3z 2-orbital featuring by far the largest amplitude due to its strong direct coupling to the s-type conduction electrons.
Http Www Theses Fr, 2012
1 : étude expérimentale avec des atomes de sodium dans un piège optique Soutenue le 25 mai 2012 d... more 1 : étude expérimentale avec des atomes de sodium dans un piège optique Soutenue le 25 mai 2012 devant le jury composé de :
Journal De Physique I, 1994
The polarisation robustness of vectorial lasers with respect to différent kinds of perturbation i... more The polarisation robustness of vectorial lasers with respect to différent kinds of perturbation is theoretically investigated in thé framework of a Landau potential approach. It is shown that usual internat and external perturbations may be classified in two main classes uniform perturbations which alter thé two eigenstates in thé same manner, and differential perturbations that favor one eigenstate with respect
When a magnetic molecule is deposited on a metallic substrate or attached to metallic contacts it... more When a magnetic molecule is deposited on a metallic substrate or attached to metallic contacts its magnetic moment may actually be screened by the conduction electrons due to the Kondo effect. In view of possible applications of molecular magnets such as nanoscale spintronics and magnetic storage devices, it is important to being able to predict whether the Kondo effect will take place or not in a given system. Also one would like to understand in detail how the Kondo effect emerges in a given situation and how it is controlled by the various parameters such as the molecular conformation and the type of substrate. Using a recently developed ab initio approach for molecular devices [1,2] that explicitly takes into account the strong electronic correlations that give rise to the Kondo effect, we have calculated the electronic structure and transport properties of different magnetic molecules coupled to nanocontacts [3] and surfaces [4]. Our calculations shed light on the complex nature of the Kondo effect in molecular-scale devices. [1] D.
Physical Review B, 2006
Contrary to the antiferromagnetic and insulating character of bulk NiO, one-dimensional chains of... more Contrary to the antiferromagnetic and insulating character of bulk NiO, one-dimensional chains of this material can become half-metallic due to the lower coordination of their atoms. Here we present ab initio electronic structure and quantum transport calculations of ideal infinitely long NiO chains and of more realistic short ones suspended between Ni electrodes. While infinite chains are insulating, short suspended chains are half-metallic minority-spin conductors which display very large magnetoresistance and a spin-valve behaviour controlled by a single atom.
Journal de Radiologie, 2007
Ultrasound guided interventional radiology
Physical Review Letters, 2009
We study the impact of dynamical correlations on the electronic structure and coherent transport ... more We study the impact of dynamical correlations on the electronic structure and coherent transport properties of Cu nanocontacts hosting a single magnetic impurity (Ni,Co,Fe) in the contact region. The strong dynamical correlations of the impurity 3d-electrons are fully taken into account by combining density functional calculations with a dynamical treatment of the impurity 3d-shell in the one-crossing approximation. We find that dynamical correlations give rise to the Kondo effect and lead to Fano features in the coherent transport characteristics similar to those observed in related experiments.
Physical Review B, 2006
We show how to extract the orbital contribution to the transport eigenchannels from a firstprinci... more We show how to extract the orbital contribution to the transport eigenchannels from a firstprinciples quantum transport calculation in a nanoscopic conductor. This is achieved by calculating and diagonalizing the first-principles transmission matrix reduced to selected scattering crosssections. As an example, the orbital nature of the eigenchannels in the case of Ni nanocontacts is explored, stressing the difficulties inherent to the use of non-orthogonal basis sets
Physical Review B, 2010
We present an approach for calculating the electronic structure and transport properties of nanos... more We present an approach for calculating the electronic structure and transport properties of nanoscopic conductors that takes into account the dynamical correlations of strongly interacting d-or f-electrons by combining density functional theory calculations with the dynamical mean-field theory. While the density functional calculation yields a static mean-field description of the weakly interacting electrons, the dynamical mean-field theory explicitly takes into account the dynamical correlations of the strongly interacting d-or f-electrons of transition metal atoms. As an example we calculate the electronic structure and conductance of Ni nanocontacts between Cu electrodes. We find that the dynamical correlations of the Ni 3d-electrons give rise to quasi-particle resonances at the Fermi-level in the spectral density. The quasi-particle resonances in turn lead to Fano lineshapes in the conductance characteristics of the nanocontacts similar to those measured in recent experiments of magnetic nanocontacts.
Physical Review B, 2004
ABSTRACT Charge localization seems unlikely to occur in two vertically coupled symmetric quantum ... more ABSTRACT Charge localization seems unlikely to occur in two vertically coupled symmetric quantum dots even if a small bias voltage breaks the exact isospin-symmetry of the system. However for a three-electron double quantum dot we find a strong localization of charges at certain vertically applied magnetic fields. The charge localization is directly connected to new ground state transitions between eigenstates differing only in parity. The transitions are driven by magnetic field dependent Coulomb correlations between the electrons and give rise to strong isospin blockade signatures in transport through the double dot system.
Physical Review A, 2012
We study experimentally the equilibrium phase diagram of a spin 1 Bose-Einstein condensate with a... more We study experimentally the equilibrium phase diagram of a spin 1 Bose-Einstein condensate with antiferromagnetic interactions, in a regime where spin and spatial degrees of freedom are decoupled. For a given total magnetization mz, we observe for low magnetic fields an "antiferromagnetic" phase where atoms condense in the m = ±1 Zeeman states, and occupation of the m = 0 state is suppressed. Conversely, for large enough magnetic fields, a phase transition to a "broken axisymmetry" phase takes place: The m = 0 component becomes populated and rises sharply above a critical field Bc(mz). This behavior results from the competition between antiferromagnetic spin-dependent interactions (dominant at low fields) and the quadratic Zeeman energy (dominant at large fields). We compare the measured Bc as well as the global shape of the phase diagram with mean-field theory, and find good quantitative agreement.
Optics Letters, 1995
The high sensitivity of the eigenstates of a large-finesse passive Fabry-Perot cavity is used to ... more The high sensitivity of the eigenstates of a large-finesse passive Fabry-Perot cavity is used to measure the residual anisotropy of supermirrors at strictly normal incidence. An experimental demonstration leads to the measurement of phase retardances of the order of 10 26 rad.
Nature Nanotechnology, 2013
The properties of quantum systems interacting with their environment, commonly called open quantu... more The properties of quantum systems interacting with their environment, commonly called open quantum systems, can be strongly affected by this interaction. While this can lead to unwanted consequences, such as causing decoherence in qubits used for quantum computation 1 , it can also be exploited as a probe of the environment. For example, magnetic resonance imaging is based on the dependence of the spin relaxation times of protons 2 in water molecules in a host's tissue 3. Here we show that the excitation energy of a single spin, which is determined by magnetocrystalline anisotropy and controls its stability and suitability for use in magnetic data storage devices 4 , can be modified by varying the exchange coupling of the spin to a nearby conductive electrode. Using scanning tunnelling microscopy and spectroscopy, we observe variations up to a factor of two of the spin excitation energies of individual atoms as the strength of the spin's coupling to the surrounding electronic bath changes. These observations, combined with calculations, show that exchange coupling can strongly modify the magnetic anisotropy. This system is thus one of the few open quantum systems in which the energy levels, and not just the excited-state lifetimes, can be controllably
Nature, 2009
Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk, electronic conduction in th... more Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk, electronic conduction in these materials takes place mainly through the s and p electrons, whereas the magnetic moments are mostly in the narrow d-electron bands, where they tend to align. This general picture may change at the nanoscale because electrons at the surfaces of materials experience interactions that differ from those in the bulk. Here we show direct evidence for such changes: electronic transport in atomic-scale contacts of pure ferromagnets (iron, cobalt and nickel), despite their strong bulk ferromagnetism, unexpectedly reveal Kondo physics, that is, the screening of local magnetic moments by the conduction electrons below a characteristic temperature 1. The Kondo effect creates a sharp resonance at the Fermi energy, affecting the electrical properties of the system;this appears as a Fano-Kondo resonance 2 in the conductance characteristics as observed in other artificial nanostructures 3,