Lasers incorporating two-dimensional photonic crystal mirrors

Photonic bandgap crystals are expected to be of use in defining microcavities for modifying spontaneous emission and as highly reflective mirrors. There are several reports of microfabricating one-dimensional structure. Here, we describe the incorporation of a microfabricated two-dimensional photonic lattice in an edge-emitting semiconductor laser structure. We demonstrate laser operation in a cavity formed between a cleaved facet and a microfabricated periodic lattice

Plankton patchiness investigated using simultaneous nitrate and chlorophyll observations

The complex patterns observed in marine phytoplankton distributions arise from the interplay of biological and physical processes, but the nature of the balance remains uncertain centuries after the first observations. Previous observations have shown a consistent trend of decreasing variability with decreasing length-scale. Influenced by similar scaling found for the properties of the water that the phytoplankton inhabit, ‘universal' theories have been proposed that simultaneously explain the variability seen from meters to hundreds of kilometers. However, data on the distribution of phytoplankton alone has proved insufficient to differentiate between the many causal mechanisms that have been suggested. Here we present novel observations from a cruise in the North Atlantic in which fluorescence (proxy for phytoplankton), nitrate and temperature were measured simultaneously at scales from 10 m to 100 km for the first time in the open ocean. These show a change in spectra between the small scale (10–100 m) and the mesoscale (10–100 km) which is different for the three tracers. We discuss these observations in relation to the current theories for phytoplankton patchiness

Plankton patchiness investigated using simultaneous nitrate and chlorophyll observations

The complex patterns observed in marine phytoplankton distributions arise from the interplay of biological and physical processes, but the nature of the balance remains uncertain centuries after the first observations. Previous observations have shown a consistent trend of decreasing variability with decreasing length-scale. Influenced by similar scaling found for the properties of the water that the phytoplankton inhabit, ‘universal' theories have been proposed that simultaneously explain the variability seen from meters to hundreds of kilometers. However, data on the distribution of phytoplankton alone has proved insufficient to differentiate between the many causal mechanisms that have been suggested. Here we present novel observations from a cruise in the North Atlantic in which fluorescence (proxy for phytoplankton), nitrate and temperature were measured simultaneously at scales from 10 m to 100 km for the first time in the open ocean. These show a change in spectra between the small scale (10–100 m) and the mesoscale (10–100 km) which is different for the three tracers. We discuss these observations in relation to the current theories for phytoplankton patchiness

Braggoriton--Excitation in Photonic Crystal Infiltrated with Polarizable Medium

Light propagation in a photonic crystal infiltrated with polarizable molecules is considered. We demonstrate that the interplay between the spatial dispersion caused by Bragg diffraction and polaritonic frequency dispersion gives rise to novel propagating excitations, or braggoritons, with intragap frequencies. We derive the braggoriton dispersion relation and show that it is governed by two parameters, namely, the strength of light-matter interaction and detuning between the Bragg frequency and that of the infiltrated molecules. We also study defect-induced states when the photonic band gap is divided into two subgaps by the braggoritonic branches and find that each defect creates two intragap localized states inside each subgap.Comment: LaTeX, 8 pages, 5 figure

An observational assessment of the influence of mesoscale and submesoscale heterogeneity on ocean biogeochemical reactions

Numerous observations demonstrate that considerable spatial variability exists in components of the marine planktonic ecosystem at the mesoscale and submesoscale (100?km -1?km). The causes and consequences of physical processes at these scales (‘eddy advection’) influencing biogeochemistry have received much attention. Less studied, the non-linear nature of most ecological and biogeochemical interactions means that such spatial variability has consequences for regional estimates of processes including primary production and grazing, independent of the physical processes. This effect has been termed ‘eddy reactions’. Models remain our most powerful tools for extrapolating hypotheses for biogeochemistry to global scales and to permit future projections. The spatial resolution of most climate and global biogeochemical models means that processes at the mesoscale and submesoscale are poorly resolved. Modelling work has previously suggested that the neglected ‘eddy reactions’ may be almost as large as the mean field estimates in some cases. This study seeks to quantify the relative size of eddy and mean reactions observationally, using in situ and satellite data. For primary production, grazing and zooplankton mortality the eddy reactions are between 7% and 15% of the mean reactions. These should be regarded as preliminary estimates to encourage further observational estimates, and not taken as a justification for ignoring eddy reactions. Compared to modelling estimates, there are inconsistencies in the relative magnitude of eddy reactions and in correlations which are a major control on their magnitude. One possibility is that models exhibit much stronger spatial correlations than are found in reality, effectively amplifying the magnitude of eddy reactions

Quantifying mesoscale-driven nitrate supply: a case study

The supply of nitrate to surface waters plays a crucial role in maintaining marine life. Physical processes at the mesoscale (~10-100?km) and smaller have been advocated to provide a major fraction of the global supply. Whilst observational studies have focussed on well-defined features, such as isolated eddies, the vertical circulation and nutrient supply in a typical 100-200?km square of ocean will involve a turbulent spectrum of interacting, evolving and decaying features. A crucial step in closing the ocean nitrogen budget is to be able to rank the importance of mesoscale fluxes against other sources of nitrate for surface waters for a representative area of open ocean. While this has been done using models, the vital observational equivalent is still lacking.To illustrate the difficulties that prevent us from putting a global estimate on the significance of the mesoscale observationally, we use data from a cruise in the Iceland Basin where vertical velocity and nitrate observations were made simultaneously at the same high spatial resolution. Local mesoscale nitrate flux is found to be an order of magnitude greater than that due to small-scale vertical mixing and exceeds coincident nitrate uptake rates and estimates of nitrate supply due to winter convection. However, a non-zero net vertical velocity for the region introduces a significant bias in regional estimates of the mesoscale vertical nitrate transport. The need for synopticity means that a more accurate estimate can not be simply found by using a larger survey area. It is argued that time-series, rather than spatial surveys, may be the best means to quantify the contribution of mesoscale processes to the nitrate budget of the surface ocean

Observed multivariable signals of late 20th and early 21st century volcanic activity

The relatively muted warming of the surface and lower troposphere since 1998 has attracted considerable attention. One contributory factor to this “warming hiatus” is an increase in volcanically induced cooling over the early 21st century. Here we identify the signals of late 20th and early 21st century volcanic activity in multiple observed climate variables. Volcanic signals are statistically discernible in spatial averages of tropical and near-global SST, tropospheric temperature, net clear-sky short-wave radiation, and atmospheric water vapor. Signals of late 20th and early 21st century volcanic eruptions are also detectable in near-global averages of rainfall. In tropical average rainfall, however, only a Pinatubo-caused drying signal is identifiable. Successful volcanic signal detection is critically dependent on removal of variability induced by the El Nino–Southern Oscillation.National Science Foundation (U.S.) (Grant AGS-1342810

Observation and Assignment of Silent and Higher Order Vibrations in the Infrared Transmission of C60 Crystals

We report the measurement of infrared transmission of large C60 single crystals. The spectra exhibit a very rich structure with over 180 vibrational absorptions visible in the 100 - 4000 cm-1 range. Many silent modes are observed to have become weakly IR-active. We also observe a large number of higher order combination modes. The temperature (77K - 300K) and pressure (0 - 25KBar) dependencies of these modes were measured and are presented. Careful analysis of the IR spectra in conjunction with Raman scattering data showing second order modes and neutron scattering data, allow the selection of the 46 vibrational modes C60. We are able to fit *all* of the first and second order data seen in the present IR spectra and the previously published Raman data (~300 lines total), using these 46 modes and their group theory allowed second order combinations.Comment: REVTEX v3.0 in LaTeX. 12 pages. 8 Figures by request. c60lon

Associations of vomiting and antiemetic use in pregnancy with levels of circulating GDF15 early in the second trimester: A nested case-control study.

Background: Although nausea and vomiting are very common in pregnancy, their pathogenesis is poorly understood. We tested the hypothesis that circulating growth and differentiation factor 15 (GDF15) concentrations in early pregnancy, whose gene is implicated in hyperemesis gravidarum, are associated with nausea and vomiting. Methods: Blood samples for the measurement of GDF15 and human chorionic gonadotrophin (hCG) concentrations were obtained early in the second trimester (median 15.1 (interquartile range 14.4-15.7) weeks) of pregnancy from 791 women from the Cambridge Baby Growth Study, a prospective pregnancy and birth cohort. During each trimester participants completed a questionnaire which included questions about nausea, vomiting and antiemetic use. Associations with pre-pregnancy body mass indexes (BMI) were validated in 231 pregnant NIPTeR Study participants. Results: Circulating GDF15 concentrations were higher in women reporting vomiting in the second trimester than in women reporting no pregnancy nausea or vomiting: 11,581 (10,977-12,219) (n=175) vs. 10,593 (10,066-11,147) (n=193) pg/mL, p=0.02). In women who took antiemetic drugs during pregnancy (n=11) the GDF15 levels were also raised 13,157 (10,558-16,394) pg/mL (p =0.04). Serum GFD15 concentrations were strongly positively correlated with hCG levels but were inversely correlated with maternal BMIs, a finding replicated in the NIPTeR Study. Conclusions: Week 15 serum GDF15 concentrations are positively associated with second trimester vomiting and maternal antiemetic use in pregnancy. Given GDF15's site of action in the chemoreceptor trigger zone of the brainstem and its genetic associations with hyperemesis gravidarum, these data support the concept that GDF15 may be playing a pathogenic role in pregnancy-associated vomiting.This work was supported by the Wellcome Trust [100574; Strategic Award]; and an unrestricted award from the Novo Nordisk Foundation (International Prize for Excellence in diabetes research) (both SOR). The Cambridge Baby Growth Study has been funded by the Medical Research Council (7500001180) (CLA), European Union Framework 5 (QLK4-1999-01422) (IAH), the Mothercare Foundation (RG54608) (IAH), Newlife Foundation for Disabled Children (07/20) (IAH), and the World Cancer Research Fund International (2004/03) (DBD). It is also supported by the National Institute for Health Research Cambridge Biomedical Research Centre. KKO and JRB are supported by the Medical Research Council (Unit Programme MC_UU_12015/2). The NIPTeR study was in part supported by an AMC-VUMC Alliance grant