475 research outputs found
Broadband terahertz heterodyne spectrometer exploiting synchrotron radiation at megahertz resolution
International audienceA new spectrometer allowing both high resolution and broadband coverage in the terahertz (THz) domain is proposed. This instrument exploits the heterodyne technique between broadband synchrotron radiation and a quantum cascade laser (QCL) based molecular THz laser that acts as the local oscillator (LO). Proof of principle for exploitation for spectroscopy is provided by the recording of molecular absorptions of hydrogen sulfide (H 2 S) and methanol (CH 3 OH) around 1.073 THz. Ultimately, the spectrometer will enable to cover the 1-4 THz region in 5 GHz windows at Doppler resolution
TERAHERTZ ROTATIONAL SPECTROSCOPY OF THE SO RADICAL
Author Institution: Laboratoire de Physico-Chimie de l'Atmosphere, EA 4493, Universite du Littoral Cote d'Opale, 59140 Dunkerque, France; Institut des Sciences Moleculaires d'Orsay, CNRS, UMR 8214, Universite Paris XI, bat. 210, 91405 Orsay Cedex, France; SOLEIL Synchrotron, AILES beamline, L'orme des Merisiers, Saint-Aubin, 91192 Gif-Sur-Yvette, FranceSulfur monoxide SO (X) is a well-known interstellar radical identified in a wide variety of astrophysical environments 184, L59 (1973)} which is particularly abundant in star forming regions, \textit{Astrophys. J.} 315, 621 (1987)}. Due to its high reactivity and its role in chemical reactions involving O and S atoms, SO is also a reaction intermediate in combustion processes and chemistry of the Earth atmosphere, \textit{J. Mol. Spectrosc.} 124, 379 (1987)}. %The pure rotational spectrum of SO has been extensively studied in the laboratory from sub-millimeter to THz wavelength, \textit{J. Mol. Speectrosc.} 182, 85 (1997)}. However no far infrared (FIR) broadband investigation on this radical has been reported up to date, and several rotational transitions belonging to the spectral windows of the HIFI instrument (on board of the Herschel satellite) require accurate laboratory measurements. %\vspace{1em} We have recorded pure rotational transitions of SO in the THz spectral range using synchrotron-based Fourier-Transform (FT) FIR and continous wave (CW) THz techniques. A FT-FIR spectrum of SO has been recorded at the AILES beamline of SOLEIL synchrotron in the spectral range 44--93 \wn~using a resolution of 0.001~\wn~allowing an accuracy on line position of 0.00007~\wn~( 2 MHz). A multipass absorption discharge cell aligned to an absorption path length of 24 m has been used, \textit{Rev. Sci. Instrum.} 82, 113106 (2011)}. A continuous electrical discharge (1~A / 980~V) in a flowing mixture of HS, He, H and air (respectively at pressure of 0.01, 1.15, 0.14 and 0.06~mbar) was used to produce SO. On this spectrum, 102 transitions of SO have been identified with to . Among the observed lines, 99 are detected for the first time (22 new transitions belong to the HIFI spectral windows). Due to our limited instrumental resolution, transitions involving ranging from to show unresolved fine structure triplets. Recently, in order to observe all fine structure components in the HIFI spectral windows, we have recorded a high resolution CW-THz spectrum of SO, \textit{J. Mol. Struct.} 1006, 13 (2011)}. At the time of the writing, this spectrum was under analysis
Local adaptations of Mediterranean sheep and goats through an integrative approach
Small ruminants are suited to a wide variety of habitats and thus represent promising study models for identifying genes underlying adaptations. Here, we considered local Mediterranean breeds of goats (n = 17) and sheep (n = 25) from Italy, France and Spain. Based on historical archives, we selected the breeds potentially most linked to a territory and defined their original cradle (i.e., the geographical area in which the breed has emerged), including transhumant pastoral areas. We then used the programs PCAdapt and LFMM to identify signatures of artificial and environmental selection. Considering cradles instead of current GPS coordinates resulted in a greater number of signatures identified by the LFMM analysis. The results, combined with a systematic literature review, revealed a set of genes with potentially key adaptive roles in relation to the gradient of aridity and altitude. Some of these genes have been previously implicated in lipid metabolism (SUCLG2, BMP2), hypoxia stress/lung function (BMPR2), seasonal patterns (SOX2, DPH6) or neuronal function (TRPC4, TRPC6). Selection signatures involving the PCDH9 and KLH1 genes, as well as NBEA/NBEAL1, were identified in both species and thus could play an important adaptive role
HIGH RESOLUTION THZ AND FIR SPECTROSCOPY OF SOCl
Author Institution: Laboratoire de Physico-Chimie de l'Atmosphere, EA 4493, Universite du Littoral Cote d'Opale, 59140 Dunkerque, France; Institut des Sciences Moleculaires d'Orsay, CNRS, UMR 8214, Universite Paris XI, bat. 210, 91405 Orsay Cedex, France; SOLEIL Synchrotron, AILES beamline, L'orme des Merisiers, Saint-Aubin, 91192 Gif-Sur-Yvette, FranceThionyl chloride (SOCl) is an extremely powerful oxidant widely used in industrial processes and playing a role in the chemistry of the atmosphere, \textit{J. Phys. Chem. A} 107, 6183 (2003)}. In addition, it has a molecular configuration similar to that of phosgene (COCl), and is therefore of particular interest for security and defense applications. Low resolution vibrational spectra of gas phase SOCl 22,1193 (1954)} as well as high resolution pure rotational transitions up to 25 GHz 90, 3473 (1994)} have previously been investigated. To date no high resolution data are reported at frequencies higher than 25 GHz. \vspace{1em} We have investigated the THz absorption spectrum of SOCl in the spectral region 70--650 GHz using a frequency multiplier chain coupled to a 1 m long single path cell containing a pressure of about 15 bar. At the time of the writing, about 8000 pure rotational transitions of SOCl with highest and values of 110 and 50 respectively have been assigned on the spectrum. We have also recorded the high resolution FIR spectra of SOCl in the spectral range 50--700 \wn~using synchrotron radiation at the AILES beamline of SOLEIL facility. A White-type cell aligned with an absorption path length of 150 m has been used to record, at a resolution of 0.001 \wn,~two spectra at pressures of 5 and 56 bar of SOCl. On these spectra all FIR modes of SOCl are observed ( to ) and present a resolved rotational structure. Their analysis is in progress
Advancing Tests of Relativistic Gravity via Laser Ranging to Phobos
Phobos Laser Ranging (PLR) is a concept for a space mission designed to
advance tests of relativistic gravity in the solar system. PLR's primary
objective is to measure the curvature of space around the Sun, represented by
the Eddington parameter , with an accuracy of two parts in ,
thereby improving today's best result by two orders of magnitude. Other mission
goals include measurements of the time-rate-of-change of the gravitational
constant, and of the gravitational inverse square law at 1.5 AU
distances--with up to two orders-of-magnitude improvement for each. The science
parameters will be estimated using laser ranging measurements of the distance
between an Earth station and an active laser transponder on Phobos capable of
reaching mm-level range resolution. A transponder on Phobos sending 0.25 mJ, 10
ps pulses at 1 kHz, and receiving asynchronous 1 kHz pulses from earth via a 12
cm aperture will permit links that even at maximum range will exceed a photon
per second. A total measurement precision of 50 ps demands a few hundred
photons to average to 1 mm (3.3 ps) range precision. Existing satellite laser
ranging (SLR) facilities--with appropriate augmentation--may be able to
participate in PLR. Since Phobos' orbital period is about 8 hours, each
observatory is guaranteed visibility of the Phobos instrument every Earth day.
Given the current technology readiness level, PLR could be started in 2011 for
launch in 2016 for 3 years of science operations. We discuss the PLR's science
objectives, instrument, and mission design. We also present the details of
science simulations performed to support the mission's primary objectives.Comment: 25 pages, 10 figures, 9 table
Coupled calcium and inorganic carbon uptake suggested by magnesium and sulfur incorporation in foraminiferal calcite
Shell chemistry of foraminiferal carbonate proves to be
useful in reconstructing past ocean conditions. A new addition to the proxy
toolbox is the ratio of sulfur (S) to calcium (Ca) in foraminiferal shells,
reflecting the ratio of SO42- to CO32- in seawater. When
comparing species, the amount of SO42- incorporated, and therefore
the S∕Ca of the shell, increases with increasing magnesium (Mg) content. The
uptake of SO42- in foraminiferal calcite is likely connected to
carbon uptake, while the incorporation of Mg is more likely related to Ca
uptake since this element substitutes for Ca in the crystal lattice. The
relation between S and Mg incorporation in foraminiferal calcite therefore
offers the opportunity to investigate the timing of processes involved in Ca
and carbon uptake. To understand how foraminiferal S∕Ca is related to Mg∕Ca,
we analyzed the concentration and within-shell distribution of S∕Ca of three
benthic species with different shell chemistry: Ammonia tepida, Bulimina marginata and Amphistegina lessonii. Furthermore, we
investigated the link between Mg∕Ca and S∕Ca across species and the
potential influence of temperature on foraminiferal S∕Ca. We observed that
S∕Ca is positively correlated with Mg∕Ca on a microscale within specimens, as
well as between and within species. In contrast, when shell Mg∕Ca increases
with temperature, foraminiferal S∕Ca values remain similar. We evaluate our
findings in the light of previously proposed biomineralization models and
abiological processes involved during calcite precipitation. Although all
kinds of processes, including crystal lattice distortion and element
speciation at the site of calcification, may contribute to changes in either
the amount of S or Mg that is ultimately incorporated in foraminiferal
calcite, these processes do not explain the covariation between Mg∕Ca and
S∕Ca values within specimens and between species. We observe that groups of
foraminifera with different calcification pathways, e.g., hyaline versus
porcelaneous species, show characteristic values for S∕Ca and Mg∕Ca, which
might be linked to a different calcium and carbon uptake mechanism in
porcelaneous and hyaline foraminifera. Whereas Mg incorporation might be
controlled by Ca dilution at the site of calcification due to Ca pumping, S
is linked to carbonate ion concentration via proton pumping. The fact that
we observe a covariation of S and Mg within specimens and between species
suggests that proton pumping and Ca pumping are intrinsically coupled across
multiple scales.</p
Recommended from our members
SEIS: Insight's Seismic Experiment for Internal Structure of Mars.
By the end of 2018, 42 years after the landing of the two Viking seismometers on Mars, InSight will deploy onto Mars' surface the SEIS (Seismic Experiment for Internal Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz, with possible extension to longer periods. Data will be transmitted in the form of three continuous VBB components at 2 sample per second (sps), an estimation of the short period energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at 10 sps. The continuous streams will be augmented by requested event data with sample rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Viking's Mars seismic monitoring by a factor of ∼ 2500 at 1 Hz and ∼ 200 000 at 0.1 Hz. An additional major improvement is that, contrary to Viking, the seismometers will be deployed via a robotic arm directly onto Mars' surface and will be protected against temperature and wind by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is reasonable to infer a moment magnitude detection threshold of M w ∼ 3 at 40 ∘ epicentral distance and a potential to detect several tens of quakes and about five impacts per year. In this paper, we first describe the science goals of the experiment and the rationale used to define its requirements. We then provide a detailed description of the hardware, from the sensors to the deployment system and associated performance, including transfer functions of the seismic sensors and temperature sensors. We conclude by describing the experiment ground segment, including data processing services, outreach and education networks and provide a description of the format to be used for future data distribution.Electronic supplementary materialThe online version of this article (10.1007/s11214-018-0574-6) contains supplementary material, which is available to authorized users
Evolutionary optimisation of neural network models for fish collective behaviours in mixed groups of robots and zebrafish
Animal and robot social interactions are interesting both for ethological
studies and robotics. On the one hand, the robots can be tools and models to
analyse animal collective behaviours, on the other hand, the robots and their
artificial intelligence are directly confronted and compared to the natural
animal collective intelligence. The first step is to design robots and their
behavioural controllers that are capable of socially interact with animals.
Designing such behavioural bio-mimetic controllers remains an important
challenge as they have to reproduce the animal behaviours and have to be
calibrated on experimental data. Most animal collective behavioural models are
designed by modellers based on experimental data. This process is long and
costly because it is difficult to identify the relevant behavioural features
that are then used as a priori knowledge in model building. Here, we want to
model the fish individual and collective behaviours in order to develop robot
controllers. We explore the use of optimised black-box models based on
artificial neural networks (ANN) to model fish behaviours. While the ANN may
not be biomimetic but rather bio-inspired, they can be used to link perception
to motor responses. These models are designed to be implementable as robot
controllers to form mixed-groups of fish and robots, using few a priori
knowledge of the fish behaviours. We present a methodology with multilayer
perceptron or echo state networks that are optimised through evolutionary
algorithms to model accurately the fish individual and collective behaviours in
a bounded rectangular arena. We assess the biomimetism of the generated models
and compare them to the fish experimental behaviours.Comment: 10 pages, 4 figure
- …