Quantum dynamics of a dc-SQUID coupled to an asymmetric Cooper pair transistor

We present a theoretical analysis of the quantum dynamics of a superconducting circuit based on a highly asymmetric Cooper pair transistor (ACPT) in parallel to a dc-SQUID. Starting from the full Hamiltonian we show that the circuit can be modeled as a charge qubit (ACPT) coupled to an anharmonic oscillator (dc-SQUID). Depending on the anharmonicity of the SQUID, the Hamiltonian can be reduced either to one that describes two coupled qubits or to the Jaynes-Cummings Hamiltonian. Here the dc-SQUID can be viewed as a tunable micron-size resonator. The coupling term, which is a combination of a capacitive and a Josephson coupling between the two qubits, can be tuned from the very strong- to the zero-coupling regimes. It describes very precisely the tunable coupling strength measured in this circuit and explains the 'quantronium' as well as the adiabatic quantum transfer read-out.Comment: 20 page

Species Profiles: Life Histories and Environmental Requirements of Coastal Fishes and Invertebrates (Mid-Atlantic): Alewife/Blueback Herring

This profile covers life history and environmental requirements of both alewife (Alosa pseudoharengus) and blueback herring (Alosa aestivalis), since their distribution is overlapping and their morphology, ecological role, and environmental requirements are similar. The alewife is an anadromous species found in riverine, estuarine, and Atlantic coastal habitats, depending on life cycle stage, from Newfoundland (Winters et al. 1973) to Soutn Carolina (Berry 1964). Landlocked populations are i n the Great Lakes, Finger Lakes, and many other freshwater lakes (Bigelow and Sch roeder 1953; Scott and Crossman 1973). The blueback herring is an anadromous species found in riverine, estuarine, and Atlantic coastal habitats, depending on life stage cycle, from Nova Scotia to the St. Johns River, Florida (Hildebrand 1963

Fluorescent visualization of a spreading surfactant

The spreading of surfactants on thin films is an industrially and medically important phenomenon, but the dynamics are highly nonlinear and visualization of the surfactant dynamics has been a long-standing experimental challenge. We perform the first quantitative, spatiotemporally-resolved measurements of the spreading of an insoluble surfactant on a thin fluid layer. During the spreading process, we directly observe both the radial height profile of the spreading droplet and the spatial distribution of the fluorescently-tagged surfactant. We find that the leading edge of spreading circular layer of surfactant forms a Marangoni ridge in the underlying fluid, with a trough trailing the ridge as expected. However, several novel features are observed using the fluorescence technique, including a peak in the surfactant concentration which trails the leading edge, and a flat, monolayer-scale spreading film which differs from concentration profiles predicted by current models. Both the Marangoni ridge and surfactant leading edge can be described to spread as $R \propto t^{\delta}$. We find spreading exponents, $\delta_H \approx 0.30$ and $\delta_\Gamma \approx 0.22$ for the ridge peak and surfactant leading edge, respectively, which are in good agreement with theoretical predictions of $\delta = 1/4$. In addition, we observe that the surfactant leading edge initially leads the peak of the Marangoni ridge, with the peak later catching up to the leading edge

Energy relaxation in graphene and its measurement with supercurrent

We study inelastic energy relaxation in graphene for low energies to find out how electrons scatter with acoustic phonons and other electrons. By coupling the graphene to superconductors, we create a strong dependence of the measured signal, i.e.,\ critical Josephson current, on the electron population on different energy states. Since the relative population of high- and low-energy states is determined by the inelastic scattering processes, the critical current becomes an effective probe for their strength. We argue that the electron-electron interaction is the dominant relaxation method and, in our model of two-dimensional electron-electron scattering, we find a scattering time $\tau_{e-e}=5... 13$ ps at T=500 mK, 1-2 orders of magnitude smaller than predicted by theory.Comment: 10 pages, 13 figures submitted to Physical Review

Specific heat and thermal conductivity in the mixed state of MgB2

The specific heat C and the electronic and phononic thermal conductivities kappa_e and kappa_{ph} are calculated in the mixed state for magnetic fields H near H_{c2}. The effects of supercurrent flow and Andreev scattering of the Abrikosov vortex lattice on the quasiparticles are taken into account. The resulting function C(H) is nearly linear while kappa_e(H) exhibits an upward curvature near H_{c2}. The slopes decrease with impurity scattering which improves the agreement with the data on MgB_2. The ratio of phonon relaxation times tau_n/tau_s = g(omega_0,H) for phonon energy omega_0, which is nearly a step function at omega_0 = 2Delta for the BCS state, is smeared out and tends to one for increasing H. This leads to a rapid reduction of kappa_{ph}(H) in MgB_2 for relatively small fields due to the rapid suppression of the smaller energy gap.Comment: 8 pages, 4 figures, accepted for publication in Phys. Rev. Letter

Molecular Studies of Subfamily Gilliesioideae (Alliaceae)

We present an analysis of relationships in Gilliesioideae (Alliaceae) based on a combined matrix of plastid rbcL, the trnL intron, the trnL-F intergenic spacer, and the rps16 intron and nuclear ITS ribosomal DNA sequences. The results are generally congruent with previous analyses, indicating two well-supported groups: Ipheion plus allied genera ( lpheieae ined.) and Gilliesieae. They also provide higher bootstrap support for many patterns of relationships. Polyphyly of lpheion and Nothoscordum is confirmed. Increased taxon sampling (particularly in Gilliesieae) and additional molecular data would be desirable to provide further resolution and to allow an appropriate taxonomic revision to be made

Integrating TV/digital data spectrograph system

A 25-mm vidicon camera was previously modified to allow operation in an integration mode for low-light-level astronomical work. The camera was then mated to a low-dispersion spectrograph for obtaining spectral information in the 400 to 750 nm range. A high speed digital video image system was utilized to digitize the analog video signal, place the information directly into computer-type memory, and record data on digital magnetic tape for permanent storage and subsequent analysis

The Struck-and-lost Factor in Alaskan Walrus Harvests, 1952-1972

Struck-and-lost rates during hunts for walruses, Odobenus rosmarus (Linnaeus), in Alaska from 1952 to 1972 did not vary from year to year. On average, 42% of the animals struck by bullets were lost (i.e., not retrieved). About 55% of the struck-and lost animals died immediately; the rest were wounded. Apparently, most of the wounded died soon after they were struck. The sex-age composition of the struck-and-lost animals was about the same as that in the harvest, and the proportion lost did not vary with the size of the group encountered. Claims of reduction in loss rates in recent years, based on improved firepower, are open to question. Considerable improvement in weapons took place also during the 21-year period of this study, but it merely increased the proportion of outright kills among the struck-and-lost animals. It did not reduce the proportion lost of the animals that were struck.Key words: walrus, Odobenus rosmarus, Alaska, harvests, struck-and-lostLe taux d'animaux frappés et perdus au cours de la chasse au morse, Odobenus rosmarus (Linnaeus) en Alaska de 1952 à 1972 n'a pas varié d'une année à l'autre. En moyenne, 42 p. cent des animaux frappés par les balles ont été perdus (c.-à-d. non récupérés). Environ 55 p. cent des animaux frappés et perdus sont morts sur le coup et 45 p. cent ont été blessés. Il semble que la plupart de ces derniers soient morts peu de temps après avoir été frappés. La composition selon le sexe et l'âge des animaux frappés et perdus était environ la même que celle des prises, et la proportion des animaux perdus ne variait pas avec la taille du groupe chassé. On peut remettre en question les affirmations des dernières années concernant une réduction du taux de perte causée par l'amélioration de la puissance de feu. Durant les 21 années de l'étude, les armes ont subi de grosses améliorations, mais celles-ci ont tout simplement fait augmenter la proportion des bêtes tuées sur le coup, parmi les animaux qui avaient été frappés et perdus. Les améliorations apportées aux armes n'ont pas réduit la proportion des animaux perdus parmi ceux qui avaient été frappés.Mots clés: morse, Odobenus rosmarus, Alaska, prises, frappés et perdu

Factorization of the Two Loop Four-Particle Amplitude in Superstring Theory Revisited

We study in detail the factorization of the newly obtained two-loop four-particle amplitude in superstring theory. In particular some missing factors from the scalar correlators are obtained correctly, in comparing with a previous study of the factorization in two-loop superstring theory. Some details for the calculation of the factorization of the kinematic factor are also presented.Comment: 11 pages, 1 figure; v2, minor corrections and references update