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  • American Institute of Physics (AIP)  (5)
  • American Physical Society (APS)  (2)
  • American Association for the Advancement of Science (AAAS)  (1)
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  • 1
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    Communication: Fully coherent quantum state hopping (2015)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2015-10-10
    Description: In this paper, we describe a new and fully coherent stochastic surface hopping method for simulating mixed quantum-classical systems. We illustrate the approach on the simple but unforgiving problem of quantum evolution of a two-state quantum system in the limit of unperturbed pure state dynamics and for dissipative evolution in the presence of both stationary and nonstationary random environments. We formulate our approach in the Liouville representation and describe the density matrix elements by ensembles of trajectories. Population dynamics are represented by stochastic surface hops for trajectories representing diagonal density matrix elements. These are combined with an unconventional coherent stochastic hopping algorithm for trajectories representing off-diagonal quantum coherences. The latter generalizes the binary (0,1) “probability” of a trajectory to be associated with a given state to allow integers that can be negative or greater than unity in magnitude. Unlike existing surface hopping methods, the dynamics of the ensembles are fully entangled, correctly capturing the coherent and nonlocal structure of quantum mechanics.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Regulated virulence controls the ability of a pathogen to compete with the gut microbiota (2012)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2012-05-15
    Description: The virulence mechanisms that allow pathogens to colonize the intestine remain unclear. Here, we show that germ-free animals are unable to eradicate Citrobacter rodentium, a model for human infections with attaching and effacing bacteria. Early in infection, virulence genes were expressed and required for pathogen growth in conventionally raised mice but not germ-free mice. Virulence gene expression was down-regulated during the late phase of infection, which led to relocation of the pathogen to the intestinal lumen where it was outcompeted by commensals. The ability of commensals to outcompete C. rodentium was determined, at least in part, by the capacity of the pathogen and commensals to grow on structurally similar carbohydrates. Thus, pathogen colonization is controlled by bacterial virulence and through competition with metabolically related commensals.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3439148/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3439148/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kamada, Nobuhiko -- Kim, Yun-Gi -- Sham, Ho Pan -- Vallance, Bruce A -- Puente, Jose L -- Martens, Eric C -- Nunez, Gabriel -- DK091191/DK/NIDDK NIH HHS/ -- DK61707/DK/NIDDK NIH HHS/ -- R01 DK061707/DK/NIDDK NIH HHS/ -- R01 DK091191/DK/NIDDK NIH HHS/ -- Canadian Institutes of Health Research/Canada -- New York, N.Y. -- Science. 2012 Jun 8;336(6086):1325-9. doi: 10.1126/science.1222195. Epub 2012 May 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Pathology and Comprehensive Cancer Center, The University of Michigan Medical School, Ann Arbor, MI 48109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22582016" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bacterial Load ; Bacterial Proteins/genetics/metabolism ; Bacteroides/*growth & development ; Citrobacter rodentium/genetics/growth & development/immunology/*pathogenicity ; Enterobacteriaceae Infections/immunology/*microbiology ; Escherichia coli/*growth & development ; Feces/microbiology ; Gene Expression Regulation, Bacterial ; Germ-Free Life ; Intestinal Mucosa/*microbiology ; Intestines/*microbiology ; *Metagenome ; Mice ; Mice, Inbred C57BL ; *Microbial Interactions ; Specific Pathogen-Free Organisms ; Virulence Factors/genetics/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Phase separation and proximity effects in itinerant ferromagnet/superconductor heterostructures (2018)
    American Physical Society (APS)
    Details
    Publication Date: 2018-11-27
    Description: Author(s): C. Martens, A. Bill, and G. Seibold Heterostructures made of itinerant ferromagnets and superconductors are studied. In contrast to most previous models, ferromagnetism is not enforced by an effective Zeeman field but induced in a correlated single-band model (CSBM) that displays itinerant ferromagnetism as a mean-field ground state. ... [Phys. Rev. B 98, 174513] Published Mon Nov 26, 2018
    Keywords: Superfluidity and superconductivity
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
    Published by American Physical Society (APS)
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  • 4
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    Entanglement dynamics with a trajectory-based formulation (2017)
    American Physical Society (APS)
    Details
    Publication Date: 2017-08-31
    Description: Author(s): Feng Xu (徐峰), Craig C. Martens, and Yujun Zheng (郑雨军) In this paper we present a trajectory-based formulation of entanglement dynamics by employing the Wigner function. The linear entropy of a single trajectory is derived based on the trajectory evolution of the Wigner function. The entanglement dynamics with a separable Gaussian initial state is inves... [Phys. Rev. A 96, 022138] Published Tue Aug 29, 2017
    Keywords: Fundamental concepts
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
    Published by American Physical Society (APS)
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  • 5
    Electronic Resource
    Electronic Resource
    The breaking and remaking of a bond: Caging of I2 in solid Kr (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6648-6657 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The caging of I2 in solid Kr is followed in real-time following its dissociative excitation on the A(3Π1u) surface. The experiments involve pump–probe measurements with a time resolution of ≥150 fs. The experimental signals are reproduced using classical molecular dynamics simulations, and the classical Franck approximation. The comparison between experiment and simulation allows an unambiguous interpretation of features in the observed signal as being due to the initial impulsive stretch of the I–I bond, collision of the atoms with the cage wall, recoil and recombination, and the subsequent coherent oscillations of the nascent I2 molecule. These detailed observations are possible due to retention of coherence along the I–I coordinate throughout the caging process. The extent of coherence is dictated mainly by the initial impact parameters of the molecule-cage collision, which in turn is controlled by the thermal and zero-point amplitudes of lattice vibrations. The caging is well-described as a sudden process, involving a binary collision between I and Kr atoms with nearly complete energy loss of the I atom upon completion of the first collision. Vibrational relaxation of the bound molecule proceeds on the time scale of 12 ps. The nontrivial relation between this relaxation time and decay rates that may be extracted from experimental transients is discussed. Although the interplay between the nested A and A' potentials is not detectable, it is clear that in the studied range of initial excess energies, 1000–1700 cm−1, the recombination remains effectively adiabatic, and does not involve the ground state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468359
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  • 6
    Electronic Resource
    Electronic Resource
    Comment on "Local frequency analysis and the structure of classical phase space of the LiNC/LiCN molecular system" [J. Chem. Phys. 108, 63 (1998)] (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6507-6507 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this Comment, we correct a misunderstanding in the title paper concerning the accuracy of the fast Fourier transform method of local frequency analysis of Martens, Davis, and Ezra. We also discuss the application of the Martens–Davis–Ezra method to a two degree of freedom model of OSC. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477298
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  • 7
    Electronic Resource
    Electronic Resource
    Semiclassical vibrational energies and transition frequencies for a Hamiltonian with stretch–bend potential energy coupling: Application of Fourier methods (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6609-6617 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Semiclassical methods are applied to determine transition frequencies and vibrational energies for the two-mode HC2 stretch–bend Hamiltonian recently studied by Swamy and Hase [J. Chem. Phys. 84, 361 (1986)]. The mean action spectral approximation for calculating transition frequencies is found to give results in excellent agreement with quantum variational values. The FFT EBK method is used to calculate vibrational eigenvalues for both nonresonant and 3:1 resonant states. Both approaches give results more accurate than those reported by Swamy and Hase using the DeLeon–Heller–Miller method. The presence of stretch–bend potential coupling is found to reduce the extent of classical chaos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453445
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  • 8
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    Low absorption loss p-AlGaN superlattice cladding layer for current-injection deep ultraviolet laser diodes (2016)
    American Institute of Physics (AIP)
    Details
    Publication Date: 2016-04-16
    Description: Current injection into AlGaN-based laser diode structures with high aluminum mole fractions for deep ultraviolet emission is investigated. The electrical characteristics of laser diode structures with different p-AlGaN short period superlattice (SPSL) cladding layers with various aluminum mole fractions are compared. The heterostructures contain all elements that are needed for a current-injection laser diode including cladding and waveguide layers as well as an AlGaN quantum well active region emitting near 270 nm. We found that with increasing aluminum content in the p-AlGaN cladding, the diode turn-on voltage increases, while the series resistance slightly decreases. By introducing an SPSL instead of bulk layers, the operating voltage is significantly reduced. A gain guided broad area laser diode structure with transparent p-Al 0.70 Ga 0.30 N waveguide layers and a transparent p-cladding with an average aluminum content of 81% was designed for strong confinement of the transverse optical mode and low optical losses. Using an optimized SPSL, this diode could sustain current densities of more than 4.5 kA/cm 2 .
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
    Published by American Institute of Physics (AIP)
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