Collaborative Reseach: Nitrogen Limitation and Ultraviolet Stress in Marine Macroalgae

Physical factors such as light, temperature and nutrient availability are known to limit marine productivity and play an important role in determining species distribution and community structure. Most understanding of the role of physical factors is based on studies with a single variable with other conditions being optimized for growth. Consequently, little information is available on physiological responses to the natural environment where several physical factors may be suboptimal. The ability to understand the constraints on marine productivity requires not only an understanding of potential synergistic or antagonistic interactions but also an analysis of their effects on algae with different ecological strategies. This investigation will examine the response of marine red macroalgae to simultaneous nitrogen limitation and ultraviolet radiation stress. Both factors are known to be important determinants of marine primary productivity and they frequently co-occur. This is true not only of the tropics, but also in cold- temperate oceans such as the Gulf of Maine. Red macroalgae were selected for this research because they provide the opportunity to study interactions between UV and nitrogen limitation in a group of algae with similar physiological and morphological characteristics but with well-defined differences in UV-tolerance and well-characterized contents of mycosporine-like amino acids. Furthermore, in contrast to phytoplankton, benthic macroalgae experience a more predictable light climate and are relatively long-lived, exposing individuals to a wider range of environmental conditions. The red algae studied from the Gulf of Maine will include Porphyra umbilicalis, Chondrus crispus, Membranoptera alata and Phycodry rubens. These species range from UV-tolerant intertidal and shallow sublittoral species to UV-susceptible species from the deeper sublittoral. The investigators anticipate that the costs and benefits of UV-tolerance and the impact of nitrogen limitation will vary between UV-tolerant and UV-susceptible species. The research will focus on the effect of nitrogen metabolism (limited or replete) on (a) short and long-term effects of UV-stress (e.g., short-tem inhibition of photosynthesis, lipid peroxidation, and growth), (b) UV-photoprotection including contents of sunscreens such as mycosporine-like amino acids (MAAs), antioxidants such as ascorbate, gluathione and tocopherols, and enzymes of reactive oxygen metabolism such as catalase, superoxide dismutase and ascorbate peroxidase, and (c) ability to recover from UV-stress (e.g., the role of protein synthesis in recovery). The research will also examine the effect of UV-stress on nitrogen metabolism (e.g., nitrogen content and rates of uptake and assimilation). The research will involve measurements on field-collected material, laboratory experiments under controlled conditions and outdoor experiments in flowing seawater and natural radiation manipulated by a variety of UV and photosynthetically active radiation (PAR)-filters. The research will substantially contribute to an understanding of the effect of UV and inorganic nitrogen availability on marine productivity and, in particular, elucidate the importance of interactions between these factors. The research involves collaboration between faculty at an undergraduate teaching institution (Westfield State College, MA) and a Land and Sea Grant research University (University of Maine). In addition to graduate education, the project has a substantial research experience for undergraduate component, providing undergraduates from Westfield State College with the opportunity to become involved in research

Schmidt Analysis of Pure-State Entanglement

We examine the application of Schmidt-mode analysis to pure state entanglement. Several examples permitting exact analytic calculation of Schmidt eigenvalues and eigenfunctions are included, as well as evaluation of the associated degree of entanglement.Comment: 5 pages, 3 figures, for C.M. Bowden memoria

Classical versus quantum dynamics for a driven relativistic oscillator

We compare the time evolution of the quantum-mechanical spatial probability density obtained by solving the time-dependent Dirac equation with its classical counterpart obtained from the relativistic Liouville equation for the phase-space density in a regime in which the dynamics is essentially relativistic. For a resonantly driven one-dimensional harmonic oscillator, the simplest nontrivial model system to perform this comparison, we find that, despite the nonlinearity induced by relativity, the classical ensemble description matches the quantum evolution remarkably well

Studies of group velocity reduction and pulse regeneration with and without the adiabatic approximation

We present a detailed semiclassical study on the propagation of a pair of optical fields in resonant media with and without adiabatic approximation. In the case of near and on resonance excitation, we show detailed calculation, both analytically and numerically, on the extremely slowly propagating probe pulse and the subsequent regeneration of a pulse via a coupling laser. Further discussions on the adiabatic approximation provide many subtle understandings of the process including the effect on the band width of the regenerated optical field. Indeed, all features of the optical pulse regeneration and most of the intricate details of the process can be obtained with the present treatment without invoke a full field theoretical method. For very far off resonance excitation, we show that the analytical solution is nearly detuning independent, a surprising result that is vigorously tested and compared to numerical calculations with very good agreement.Comment: 13 pages, 15 figures, submitted to Phys. Rev.

Schmidt number of pure bi-partite entangled states and methods of its calculation

An entanglement measure for pure-state continuous-variable bi-partite problem, the Schmidt number, is analytically calculated for one simple model of atom-field scattering.Comment: 3 pages, 1 figure; based on the poster presentation reported on the 11th International Conference on Quantum Optics (ICQO'2006, Minsk, May 26 -- 31, 2006), to be published in special issue of Optics and Spectroscop

Dephasing model for spatially extended atomic states in cyclotronlike resonances

In recent work, the formation of ring-shaped electron distributions for hydrogen atoms in resonant static magnetic-laser fields has exclusively been associated with the impact of relativity. In this note we will generalize this statement and show that the nonlinearity associated with the nuclear binding force can trigger similarly shaped steady-state charge clouds in atoms under suitable conditions. The dephasing model, based on modeling the quantum-mechanical state by a classical ensemble of quasiparticles evolving with slightly different cyclotron periods, can recover features, in the two lowest-order resonances as well as the Coulomb-field-induced charge distributions

Double Ionization by Strong Elliptically Polarized Laser Pulses

We join the tribute to Professor N.B. Delone in this memorial issue by presenting the results of new calculations on the effects of ellipticity on double ionization by short and strong near-optical laser pulses.Comment: 3 pages, 4 figures, accepted in Professor N.B. Delone's memorial issu

Multipartite entanglement characterization of a quantum phase transition

A probability density characterization of multipartite entanglement is tested on the one-dimensional quantum Ising model in a transverse field. The average and second moment of the probability distribution are numerically shown to be good indicators of the quantum phase transition. We comment on multipartite entanglement generation at a quantum phase transition.Comment: 10 pages, 6 figures, final versio