The oxygen isotopic composition of phytolith assemblages from tropical rainforest soil tops (Queensland, Australia): validation of a new paleoenvironmental tool

Phytoliths are micrometric particles of amorphous silica that form inside or between the cells of higher plant tissues throughout the life of a plant. With plant decay, phytoliths are either incorporated into soils or exported to sediments via regional watersheds. Phytolith morphological assemblages are increasingly used as proxy of grassland diversity and tree cover density in inter-tropical areas. Here, we investigate whether, along altitudinal gradients in northeast Queensland (Australia), changes in the δ<sup>18</sup>O signature of soil top phytolith assemblages reflect changes in mean annual temperature (MAT) and in the oxygen isotopic composition of precipitation (δ<sup>18</sup>O<sub>precipitation</sub>), as predicted by equilibrium temperature coefficients previously published for silica. Oxygen isotopic analyses were performed on 16 phytolith samples, after controlled isotopic exchange (CIE), using the IR Laser-Heating Fluorination Technique. Long-term mean annual precipitation (MAP) and MAT values at the sampled sites were calculated by the ANUCLIM software. δ<sup>18</sup>O<sub>precipitation</sub> estimates were calculated using the Bowen and Wilkinson (2002) model, slightly modified. An empirical temperature-dependant relationship was obtained: δ<sup>18</sup>O<sub>wood phytolith-precipitation</sub> (‰ vs. VSMOW) = −0.4 (±0.2) <i>t</i> (°C) + 46 (±3) (<i>R</i><sup>2</sup> = 0.4, <i>p</i> < 0.05; <i>n</i> = 12). Despite the various unknowns introduced when estimating δ<sup>18</sup>O<sub>precipitation</sub> values and the large uncertainties on δ<sup>18</sup>O<sub>wood phytolith</sub> values, the temperature coefficient (−0.4 ± 0.2‰ °C<sup>−1</sup>) is in the range of values previously obtained for natural quartz, fresh and sedimentary diatoms and harvested grass phytoliths (from −0.2 to −0.5‰ °C<sup>−1</sup>). The consistency supports the reliability of δ<sup>18</sup>O<sub>wood phytolith</sub> signatures for recording relative changes in mean annual δ<sup>18</sup>O<sub>soil water</sub> values (which are assumed to be equivalent to the weighted annual δ<sup>18</sup>O<sub> precipitation</sub> values in rainforests environments) and MAT, provided these changes were several ‰ and/or several °C in magnitude

Trust Central Eases Funding Decisions With Data

The Children’s Trust is a local government taxing authority that uses property tax dollars to fund programming for Miami-Dade County children and families. To become more efficient, Trust Central was created and now automates our full business cycle. Data flow is solicitation → contracting → program metrics → solicitation. Agencies apply for funding, contract to provide services, report their progress. Their progress is used to determine future solicitation criteria. Data automatically flows from one module to another. Trust Central allowed us to move from using 5 data points to make funding decisions to 24 data points. We were able to look across our various initiatives to ensure that our funding decisions were equitable. Funding decisions were backed by data and easy to share with applicants. We created context and communicated funding decisions in a way that reduced emotional conflicts and appeals. As a reference point, we had 96 appeal meetings last funding cycle - this funding cycle no appeal meetings and only 19 review meetings; a cost savings of $15,850 in meetings. Another reference point, we spent 1 week reviewing data to make funding decisions last funding cycle - this funding cycle we spent 4 weeks reviewing data in a more meaningful and valuable way. We made$68M in funding decisions without any negative feedback from the community. Our relationship with the community pivoted from negative to positive. This is a first for us! We are now positioned to be a mentor for both governmental and non-governmental funders

Obstacles, levers and impacts of organic farming development in Camargue

We are presenting an analysis of the obstacles and levers for the development of organic cropping systems in Camargue, documented with a multicriteria analysis of scenarios of organic farming (OF) development. This communication is built using results from on-farm agronomic monitoring, stakeholders and farmers’ interviews and the use of models for integrated assessment of scenarios. At the farm level, the obstacles are related to identification of profitable cropping systems and rotations that include enough rice, conversion being therefore risky as impacting financial management and requiring a labour reorganisation. At the regional level, the constraints are related to the absence of advisory services for technical issues, and to the lack of coordination among the different stakeholders, to the low incentive of the public policies to convert, and to a relatively opaque organization of the supply chains. At the regional level, we analysed the consequences of two scenarios related to OF development on criteria such as the rice surface area, the quantity and quality of water, energy consumption or the employment generated. These results are expected to contribute to the definition of an action plan about OF development by the local stakeholders

Голод 1946–1947 рр. як продовження геноциду і антиукраїнської політики влади

International audienceA diatom study, carried out on a core recovered in the Southern Altiplano (Coipasa salt lake 19 degrees S, 68 degrees W) currently almost completely dry, shows that during the last glacial maximum the Coipasa salar was entirely occupied by a large shallow lake. Available data for the northern Altiplano (Lake Titicaca, 16 degrees S, 69 degrees W) indicate a water level 17 m lower than today. This opposition is explained by decreased tropical precipitations whose effects registered by Lake Titicaca were obliterated in the Coipasa salar by increased winter precipitation. ((C) Academie des sciences/Elsevier, Paris.)

Ethane in Titan's Stratosphere from Cassini CIRS Far- and Mid-Infrared Spectra

The Cassini Composite Infrared Spectrometer (CIRS) observed thermal emission in the far- and mid-infrared (from 10 to 1500 cm(exp 1)), enabling spatiotemporal studies of ethane on Titan across the span of the Cassini mission from 2004 through 2017. Many previous measurements of ethane on Titan have relied on modeling the molecules mid-infrared (sub 12) band, centered on 822 cm(exp 1). Other bands of ethane at shorter and longer wavelengths were seen, but have not been modeled to measure ethane abundance. Spectral line lists of the far-infrared (sub 4) torsional band at 289 cm(exp 1) and the mid-infrared (sub 8) band centered at 1468 cm(exp 1) have recently been studied in the laboratory. We model CIRS observations of each of these bands (along with the (sub 12) band) separately and compare the retrieved mixing ratios from each spectral region. Nadir observations of the (sub 4) band probe the low stratosphere below 100 km. Our equatorial measurements at 289 cm(exp 1) show an abundance of (1.00.4)x10(exp 5) at 88 km from 2007 to 2017. This mixing ratio is consistent with measurements at higher altitudes, in contrast to the depletion that many photochemical models predict. Measurements from the (sub 12) and (sub 8) bands are comparable to each other, with the (sub 12) band probing an altitude range that extends deeper in the atmosphere. We suggest that future studies of planetary atmospheres may observe the (sub 8) band, enabling shorter wavelength studies of ethane. There may also be an advantage to observing both the ethane (sub 8) band and nearby methane (sub 4) band in the same spectral window

Real time noise and wavelength correlations in octave-spanning supercontinuum generation

We use dispersive Fourier transformation to measure shot-to-shot spectral instabilities in femtosecond supercontinuum generation. We study both the onset phase of supercontinuum generation with distinct dispersive wave generation, as well as a highly-unstable supercontinuum regime spanning an octave in bandwidth. Wavelength correlation maps allow interactions between separated spectral components to be identified, even when such interactions are not apparent in shot-to-shot or average measurements. Experimental results are interpreted using numerical simulations. Our results show the clear advantages of dispersive Fourier transformation for studying spectral noise during supercontinuum generation.Comment: 14 pages, 5 figure

Real-time full bandwidth measurement of spectral noise in supercontinuum generation

The ability to measure real-time fluctuations of ultrashort pulses propagating in optical fiber has provided significant insights into fundamental dynamical effects such as modulation instability and the formation of frequency-shifting rogue wave solitons. We report here a detailed study of real-time fluctuations across the full bandwidth of a fiber supercontinuum which directly reveals the significant variation in measured noise statistics across the spectrum, and which allows us to study correlations between widely separated spectral components. For two different propagation distances corresponding to the onset phase of spectral broadening and the fully-developed supercontinuum, we measure real time noise across the supercontinuum bandwidth, and we quantify the supercontinuum noise using statistical higher-order moments and a frequency-dependent intensity correlation map. We identify correlated spectral regions within the supercontinuum associated with simultaneous sideband generation, as well as signatures of pump depletion and soliton-like pump dynamics. Experimental results are in excellent agreement with simulations

LOOC UP: Locating and observing optical counterparts to gravitational wave bursts

Gravitational wave (GW) bursts (short duration signals) are expected to be associated with highly energetic astrophysical processes. With such high energies present, it is likely these astrophysical events will have signatures in the EM spectrum as well as in gravitational radiation. We have initiated a program, "Locating and Observing Optical Counterparts to Unmodeled Pulses in Gravitational Waves" (LOOC UP) to promptly search for counterparts to GW burst candidates. The proposed method analyzes near real-time data from the LIGO-Virgo network, and then uses a telescope network to seek optical-transient counterparts to candidate GW signals. We carried out a pilot study using S5/VSR1 data from the LIGO-Virgo network to develop methods and software tools for such a search. We will present the method, with an emphasis on the potential for such a search to be carried out during the next science run of LIGO and Virgo, expected to begin in 2009.Comment: 11 pages, 2 figures; v2) added acknowledgments, additional references, and minor text changes v3) added 1 figure, additional references, and minor text changes. v4) Updated references and acknowledgments. To be published in the GWDAW 12 Conf. Proc. by Classical and Quantum Gravit

Annular aperture arrays: study in the visible region of the electromagnetic spectrum

http://www.opticsinfobase.org/abstract.cfm?URI=ol-30-13-1611Baida and Van Labeke recently proposed a structure that exhibits a supertransmission of light through an array of nanometric coaxial apertures in a metallic film that has been named an annular aperture array (AAA) [Opt. Commun.209, 17 (2002); Phys. Rev. B67, 155314 (2003); J. Microsc.213, 140 (2003)]. We present the first experimental study, to our knowledge, of an AAA structure in the visible region. For technological reasons, the structure under study does not produce a supertransmission of 80% as in Baida and Van Labeke [Opt. Commun.209, 17 (2002)]. We built the nanostructure and experimentally recorded its far-field spectral response. This transmission shows only one broad band with a maximum around lambda=700 nm, giving a maximum efficiency around 17%. A finite-difference time-domain simulation reproduces quite well the obtained transmission spectrum

A close halo of large transparent grains around extreme red giant stars

Intermediate-mass stars end their lives by ejecting the bulk of their envelope via a slow dense wind back into the interstellar medium, to form the next generation of stars and planets. Stellar pulsations are thought to elevate gas to an altitude cool enough for the condensation of dust, which is then accelerated by radiation pressure from starlight, entraining the gas and driving the wind. However accounting for the mass loss has been a problem due to the difficulty in observing tenuous gas and dust tens of milliarcseconds from the star, and there is accordingly no consensus on the way sufficient momentum is transferred from the starlight to the outflow. Here, we present spatially-resolved, multi-wavelength observations of circumstellar dust shells of three stars on the asymptotic giant branch of the HR diagram. When imaged in scattered light, dust shells were found at remarkably small radii (<~ 2 stellar radii) and with unexpectedly large grains (~300 nm radius). This proximity to the photosphere argues for dust species that are transparent to starlight and therefore resistant to sublimation by the intense radiation field. While transparency usually implies insufficient radiative pressure to drive a wind, the radiation field can accelerate these large grains via photon scattering rather than absorption - a plausible mass-loss mechanism for lower-amplitude pulsating stars.Comment: 13 pages, 1 table, 6 figure