Strong photon non-linearities and photonic Mott insulators

We show, that photon non-linearities in electromagnetically induced transparency can be at least one order of magnitude larger than predicted in all previous approaches. As an application we demonstrate that, in this regime they give rise to very strong photon - photon interactions which are strong enough to make an experimental realization of a photonic Mott insulator state feasible in arrays of coupled ultra high-Q micro-cavities.Comment: minor changes, to appear in Phys. Rev. Let

Analysis of Nitrogen Loading Reductions for Wastewater Treatment Facilities and Non-Point Sources in the Great Bay Estuary Watershed

In 2009, the New Hampshire Department of Environmental Services (DES) published a proposal for numeric nutrient criteria for the Great Bay Estuary. The report found that total nitrogen concentrations in most of the estuary needed to be less than 0.3 mg N/L to prevent loss of eelgrass habitat and less than 0.45 mg N/L to prevent occurrences of low dissolved oxygen. Based on these criteria and an analysis of a compilation of data from at least seven different sources, DES concluded that 11 of the 18 subestuaries in the Great Bay Estuary were impaired for nitrogen. Under the Clean Water Act, if a water body is determined to be impaired, a study must be completed to determine the existing loads of the pollutant and the load reductions that would be needed to meet the water quality standard. Therefore, DES developed models to determine existing nitrogen loads and nitrogen loading thresholds for the subestuaries to comply with the numeric nutrient criteria. DES also evaluated the effects of different permitting scenarios for wastewater treatment facilities on nitrogen loads and the costs for wastewater treatment facility upgrades. This modeling exercise showed that: Nitrogen loads to the Great Bay, Little Bay, and the Upper Piscataqua River need to be reduced by 30 to 45 percent to attain the numeric nutrient criteria. Both wastewater treatment facilities and non-point sources will need to reduce nitrogen loads to attain the numeric nutrient criteria. The percent reduction targets for nitrogen loads only change minimally between wet and dry years. Wastewater treatment facility upgrades to remove nitrogen will be costly; however, the average cost per pound of nitrogen removed from the estuary due to wastewater facility upgrades is lower than for non-point source controls. The permitting options for some wastewater treatment facilities will be limited by requirements to not increase pollutant loads to impaired waterbodies. The numeric nutrient criteria and models used by DES are sufficiently accurate for calculating nitrogen loading thresholds for the Great Bay watershed. Additional monitoring and modeling is needed to better characterize conditions and nitrogen loading thresholds for the Lower Piscataqua River. This nitrogen loading analysis for Great Bay may provide a framework for setting nitrogen permit limits for wastewater treatment facilities and developing watershed implementation plans to reduce nitrogen loads

Decoherence due to three-body loss and its effect on the state of a Bose-Einstein condensate

A Born-Markov master equation is used to investigate the decoherence of the state of a macroscopically occupied mode of a cold atom trap due to three-body loss. In the large number limit only coherent states remain pure for times longer than the decoherence time: the time it takes for just three atoms to be lost from the trap. For large numbers of atoms (N>10^4) the decoherence time is found to be much faster than the phase collapse time caused by intra-trap atomic collisions

Phonon-assisted transitions from quantum dot excitons to cavity photons

For a single semiconductor quantum dot embedded in a microcavity, we theoretically and experimentally investigate phonon-assisted transitions between excitons and the cavity mode. Within the framework of the independent boson model we find that such transitions can be very efficient, even for relatively large exciton-cavity detunings of several millielectron volts. Furthermore, we predict a strong detuning asymmetry for the exciton lifetime that vanishes for elevated lattice temperature. Our findings are corroborated by experiment, which turns out to be in good quantitative and qualitative agreement with theory

A national level assessment of metal contamination in bats

Abstract Many populations of bat species across the globe are declining, with chemical contamination one of many potential stressors implicated in these demographic changes. Metals still contaminate a wide range of habitats, but the risks to bats remain poorly understood. This study is the first to present a national scale assessment of toxic metal (Cd, Pb) and essential trace metal (Cu, Zn) concentrations in bats. Metal concentrations in tissues (kidneys, liver, stomach -stomach content, bones and fur) were measured in 193 Pipistrellus sp. in England and Wales using ICP-MS, and compared to critical toxic concentrations for small mammals. The concentrations of metals determined in bat tissues were generally lower than those reported elsewhere. Strong positive associations were found between concentrations in tissues for a given metal (liver and kidneys for Cd, Cu and Pb; stomach and fur and fur and bones for Pb), suggesting recent as well as long term exposure to these contaminants. In addition, positive correlations between concentrations of different metals in the same tissues (Cd and Zn, Cu and Zn, Cd and Pb, Pb and Zn) suggest a co-exposure of metals to bats. Approximately 21% of the bats sampled contained residues of at least one metal at concentrations high enough to elicit toxic effects (associated with kidney damage), or to be above the upper level measured in other mammal species. Pb was found to pose the greatest risk (with 7–11% of the bats containing concentrations of toxicological concern), followed by Cu (4–9%), Zn (0.5–5.2%) and Cd (0%). Our data suggest that leaching of metals into our storage matrix, formaldehyde, may have occurred, especially for Cu. The overall findings suggest that metal contamination is an environmental stressor affecting bat populations, and that further research is needed into the direct links between metal contamination and bat population declines worldwide

Modeling evaporation, ion-beam assist, and magnetron sputtering of TiO 2 thin films over realistic timescales

Results are presented for modeling the growth of TiO2 on the rutile (110) surface. We illustrate how long time scale dynamics techniques can be used to model thin film growth at realistic growth rates. The system evolution between deposition events is achieved through an on-the-fly Kinetic Monte Carlo method, which finds diffusion pathways and barriers without prior knowledge of transitions. We examine effects of various experimental parameters, such as substrate bias, plasma density, and stoichiometry of the deposited species. Growth of TiO2 via three deposition methods has been investigated: evaporation (thermal and electron beam), ion-beam assist, and reactive magnetron sputtering. We conclude that the evaporation process produces a void filled, incomplete structure even with the low-energy ion-beam assist, but that the sputtering process produces crystalline growth. The energy of the deposition method plays an important role in the film quality

Modeling evaporation, ion-beam assist, and magnetron sputtering of TiO 2 thin films over realistic timescales

Results are presented for modeling the growth of TiO2 on the rutile (110) surface. We illustrate how long time scale dynamics techniques can be used to model thin film growth at realistic growth rates. The system evolution between deposition events is achieved through an on-the-fly Kinetic Monte Carlo method, which finds diffusion pathways and barriers without prior knowledge of transitions. We examine effects of various experimental parameters, such as substrate bias, plasma density, and stoichiometry of the deposited species. Growth of TiO2 via three deposition methods has been investigated: evaporation (thermal and electron beam), ion-beam assist, and reactive magnetron sputtering. We conclude that the evaporation process produces a void filled, incomplete structure even with the low-energy ion-beam assist, but that the sputtering process produces crystalline growth. The energy of the deposition method plays an important role in the film quality

Fur : A non-invasive approach to monitor metal exposure in bats

This paper presents a novel assessment of the use of fur as a non-invasive proxy to biomonitor metal contamination in insectivorous bats. Concentrations of metals (cadmium, copper, lead and zinc) were measured using ICP-MS in tissues (kidneys, liver, stomach and stomach content, bones and fur) obtained from 193 Pipistrellus pipistrellus/pygmaeus bats. The bats were collected across a gradient of metal pollution in England and Wales. The utility of small samples of fur as an indicator of metal exposure from the environment was demonstrated with strong relationships obtained between the concentrations of non-essential metals in fur with concentrations in stomach content, kidneys, liver and bones. Stronger relationships were observed for non-essential metals than for essential metals. Fur analyses might therefore be a useful non-invasive proxy for understanding recent, as well as long term and chronic, metal exposure of live animals. The use of fur may provide valuable information on the level of endogenous metal exposure and contamination of bat populations and communities

Quantum enhanced measurement of rotations with a spin-1 Bose-Einstein condensate in a ring trap

We present a model of a spin-squeezed rotation sensor utilizing the Sagnac effect in a spin-1 Bose-Einstein condensate in a ring trap. The two input states for the interferometer are seeded using Raman pulses with Laguerre-Gauss beams and are amplified by the bosonic enhancement of spin-exchange collisions, resulting in spin-squeezing and potential quantum enhancement of the interferometry. The ring geometry has an advantage over separated beam path atomic rotation sensors due to the uniform condensate density. We model the interferometer both analytically and numerically for realistic experimental parameters and find that significant quantum enhancement is possible, but this enhancement is partially degraded when working in a regime with strong atomic interactions