Host-Parasite Co-evolution and Optimal Mutation Rates for Semi-conservative Quasispecies

In this paper, we extend a model of host-parasite co-evolution to incorporate the semi-conservative nature of DNA replication for both the host and the parasite. We find that the optimal mutation rate for the semi-conservative and conservative hosts converge for realistic genome lengths, thus maintaining the admirable agreement between theory and experiment found previously for the conservative model and justifying the conservative approximation in some cases. We demonstrate that, while the optimal mutation rate for a conservative and semi-conservative parasite interacting with a given immune system is similar to that of a conservative parasite, the properties away from this optimum differ significantly. We suspect that this difference, coupled with the requirement that a parasite optimize survival in a range of viable hosts, may help explain why semi-conservative viruses are known to have significantly lower mutation rates than their conservative counterparts

Entropy/IP: Uncovering Structure in IPv6 Addresses

In this paper, we introduce Entropy/IP: a system that discovers Internet address structure based on analyses of a subset of IPv6 addresses known to be active, i.e., training data, gleaned by readily available passive and active means. The system is completely automated and employs a combination of information-theoretic and machine learning techniques to probabilistically model IPv6 addresses. We present results showing that our system is effective in exposing structural characteristics of portions of the IPv6 Internet address space populated by active client, service, and router addresses. In addition to visualizing the address structure for exploration, the system uses its models to generate candidate target addresses for scanning. For each of 15 evaluated datasets, we train on 1K addresses and generate 1M candidates for scanning. We achieve some success in 14 datasets, finding up to 40% of the generated addresses to be active. In 11 of these datasets, we find active network identifiers (e.g., /64 prefixes or `subnets') not seen in training. Thus, we provide the first evidence that it is practical to discover subnets and hosts by scanning probabilistically selected areas of the IPv6 address space not known to contain active hosts a priori.Comment: Paper presented at the ACM IMC 2016 in Santa Monica, USA (https://dl.acm.org/citation.cfm?id=2987445). Live Demo site available at http://www.entropy-ip.com

A multiplet table for neutral helium (4He I) with transition rates

This paper combines the precise determination of the energy levels of 4He I from calculations and experiments with theoretical transition probabilities to present multiplet tables and finding lists for the fine structure of the helium atom. The tabulated transition rates and oscillator strengths include corrections for singlet-triplet mixing and spin-orbit coupling, but not the higher order relativistic terms nor the finite nuclear mass, although the latter are tabulated for future use. The results are consistent with laboratory lifetimes and oscillator strengths, but very few measurements are accurate enough to be stringent tests. An Appendix discusses the corrections for finite nuclear mass. © 2007. The American Astronomical Society. All rights reserved

Spin-forbidden radiative decay rates from the 3′,3P 1,2 and 3′,1P 1 states of helium

We have calculated atomic helium spontaneous decay rates and absorption oscillator strengths for the spin-forbidden transitions from 3′,3P 1,2 and 3′,1P 1 to all lower 1S 0 and 3S 1 states. In particular we found A 10=44.33(4)′, s -1 for the E1 transition 3′,3P 1-1′,1S 0 and 0.1147(1) s -1 for the M2 transition 3′,3P 2-1′,1S 0. © 2011 American Physical Society

Variational calculation for the ground state of lithium and the QED corrections for Li-like ions

High-precision variational calculations using multiple basis sets in Hylleraas coordinates are presented for the 1s22s 2S state of lithium. The variational bound of -7.478 060 326(10) a.u. for the nonrelativistic energy is in good agreement with our revised experimental value of -7.47 806 034(20) a.u., thereby resolving a long-standing disrepancy. Two-electron calculations of the QED corrections are extended to three-electron systems and compared with other results. The comparison for Li-like ions up to U89+ suggests a simple interpretation for the \u27\u27screening of the Lamb shift\u27\u27 recently calculated by Cheng, Johnson, and Sapirstein [Phys. Rev. Lett. 66, 2960 (1991)]. © 1991 The American Physical Society

Stationary solutions for an electron in an intense laser field. I. Single-mode case

The Schrodinger equation for an electron and a single-mode photon field with interactions is solved by a direct method. A unique feature of these solutions is the inclusion of retardation effects in the photon field. Some interesting physical questions arising from the solutions are discussed. The Keldysh-Faisal-Reiss formula for the transition rate of multiphoton ionization modified by the inclusion of retardation effects is simplified by averaging the degenerate initial states. The result shows that the retardation effects can be calculated in terms of the radial part of the momentum wavefunction of the initial state. The physical significance of the inclusion is analysed in the near-threshold case of multiphoton ionization. The result shows that in the near-threshold case, retardation effects depend exponentially on the orbital angular momentum of the initial state. The effect vanishes for s-states, but is significant for states with high orbital angular momentum

Stationary solutions for an electron in an intense laser field. II. Multimode case

The Schrodinger equation for an electron and a multimode photon field with interactions is solved in the large-phonon-number limit by using an \u27integration\u27 method. A graphical technique different from Feynman\u27s is developed to represent the terms in the solution. By this graphical technique, all interactions between the electron and the multimode photon field are evaluated to any arbitrary order according to the number of transferred photons. The graphical technique allows one easily to write down the wavefunctions for an electron interacting with a strong photon field which contains an arbitrary number of photon modes. The two-mode case is discussed in detail as an example. Some interesting physical questions arising from the solutions are briefly discussed. As a simple application, a direct generalization of the Keldysh-Faisal-Reiss formula for the transition rate of multiphoton ionization, is given in the case where two different laser beams are applied

Many-electron radial and angular integrals in the unitary-group approach

An extension of work by Drake [Phys. Rev. A 18, 820 (1978)] to the treatment of radial and angular integrals occurring in N-electron systems is presented. It is shown that the essential results pertaining to two-electron systems adapted to Hylleraas coordinates also apply to many electrons when pairs of electrons are chosen to interact with each other in a spin-adapted basis set. These results are derived using graphical-analysis techniques in the context of the unitary-group approach. © 1992 The American Physical Society