Detection of a branched alkyl molecule in the interstellar medium: iso-propyl cyanide

The largest non-cyclic molecules detected in the interstellar medium (ISM) are organic with a straight-chain carbon backbone. We report an interstellar detection of a branched alkyl molecule, iso-propyl cyanide (i-C3H7CN), with an abundance 0.4 times that of its straight-chain structural isomer. This detection suggests that branched carbon-chain molecules may be generally abundant in the ISM. Our astrochemical model indicates that both isomers are produced within or upon dust grain ice mantles through the addition of molecular radicals, albeit via differing reaction pathways. The production of iso-propyl cyanide appears to require the addition of a functional group to a non-terminal carbon in the chain. Its detection therefore bodes well for the presence in the ISM of amino acids, for which such side-chain structure is a key characteristic.Comment: This is the author's version of the work. It is posted here by permission of the AAAS for non-commercial use. The definitive version was published in Science 345, 1584 (2014), doi:10.1126/science.125667

Chirped Pulse Spectrometer Operating at 200 GHz

The combination of electronic sources operating at high frequencies and modern microwave instrumentation has enabled the recent development of chirped-pulse spectrometers for the millimetre and THz bands. This type of instrument can operate at high resolution which is particularly suited to gas phase rotational spectroscopy. The construction of a chirped pulse spectrometer operating at 200 GHz is described in detail while attention is paid to the phase stability and the data accumulation over many cycles. Validation using carbonyl sulphide has allowed the detection limit of the instrument to be established as function of the accumulation. A large number of OCS transitions were identified using a 10 GHz chirped pulse and include the 6 most abundant isotopologues, the weakest line corresponding to the fundamental R(17) transition of 16 O 13 C 33 S with a line strength of 4.3 x 10-26 cm-1 /(molec.cm-2). The linearity of the system response for different degrees of data accumulation and transition line strength was confirmed over 4 orders of magnitudes. A simple analysis of the time domain data was demonstrated to provide the line broadening coefficient without the need for conversion by a Fourier transform. Finally, the pulse duration is discussed and optimal values are given for both Doppler limited and collisional regimes

Effet des efflorescences d’Anabaena spp. sur la qualité organoleptique de la truite arc-en ciel (Onchorynchus mykiss)

Une étude a été menée sur dix plans d’eau peu profonds et eutrophes, touchés régulièrement par des efflorescences de cyanobactéries, et en particulier le genre Anabaena (A. spiroides et A flos-aquae). La recherche de composés odorants dans les truites prélevées lors des efflorescences a permis de retrouver des concentrations significatives de géosmine (jusqu’à 850 ng•kg‑1), composé odorant lipophile connu pour être produit entre autres microorganismes par Anabaena spp.. Les analyses sensorielles ont permis de retenir des descripteurs de défauts de goût de type « terreux-moisi », avec une intensité des défauts de goût notée jusqu’à 8,3/10.L’étude en microcosme de la cinétique de fixation et de libération de la géosmine dans des truites arc-en-ciel (Onchorynchus mykiss) de 250 g a permis de conclure que l’apparition de défauts de goût significatifs dans la chair apparaît après seulement quelques heures d’exposition à la géosmine. Après 30 h en présence de géosmine, la mise en eau claire dans des conditions optimales de renouvellement permet une réduction significative des défauts sensoriels au bout de quatre jours. Une corrélation significative a été retrouvée entre les densités d’Anabaena spp. et les teneurs en géosmine retrouvées dans les truites pêchées in situ (r2 = 0,74, p < 0,01).L’étude de la relation entre l’intensité sensorielle des défauts définie par les goûteurs et les concentrations de géosmine retrouvées parallèlement dans les truites pêchées in situ et celles contaminées artificiellement a permis de définir un seuil sensoriel proche de 500 ng•kg‑1. L’apparition de tels problèmes sur ces plans d’eau souvent dédiés à la pêche de loisirs implique une gestion écologique de ces masses d’eau en amont de l’apparition des cyanobactéries.A study was conducted on ten small, eutrophic water bodies affected by cyanobacteria blooms. The genus Anabaena (A. spiroides and A. flos-aquae) is often implicated in the appearance of these blooms. The consequences of these blooms on the sensory quality of fish have been studied. Anabaena spp. produce geosmin, and this earthy-musty volatile compound is found in trout flesh with significant concentrations, up to 850 ng•kg‑1. Trout are also tainted with the presence of a repulsive flavour (intensity of bad taste up to 8.3/10).A microcosm study of the kinetics of uptake and depuration of geosmin was conducted on rainbow trout (Onchorynchus mykiss). After an exposure of 6 h to geosmin, trout are significantly tainted with the appearance of significant concentrations of geosmin in the flesh and detection of repulsive flavour by taste. After an exposure of 30 h to geosmin, an open clear-water circulation system induces an elimination of the earthy-musty compound and a progressive reduction of off‑flavor intensity. The recovery of a good sensory evaluation for trout is obtained after more than four days.A significant correlation was found between Anabaena spp. density and geosmin concentrations in trout flesh (r2 = 0.74, p < 0.01). The sensory threshold of geosmin in trout by the panel of assessors is relatively low (500 ng•kg‑1) for samples collected in situ and for trout exposed artificially to geosmin. The management of off-flavour problems in these fishing water bodies requires the use of preventive methods before the appearance of cyanobacteria

Astrochemistry During the Formation of Stars

Star-forming regions show a rich and varied chemistry, including the presence of complex organic molecules - both in the cold gas distributed on large scales, and in the hot regions close to young stars where protoplanetary disks arise. Recent advances in observational techniques have opened new possibilities for studying this chemistry. In particular, the Atacama Large Millimeter/submillimeter Array (ALMA) has made it possible to study astrochemistry down to Solar System size scales, while also revealing molecules of increasing variety and complexity. In this review, we discuss recent observations of the chemistry of star-forming environments, with a particular focus on complex organic molecules, taking context from the laboratory experiments and chemical models that they have stimulated. The key takeaway points are: The physical evolution of individual sources plays a crucial role in their inferred chemical signatures, and remains an important area for observations and models to elucidate. Comparisons of the abundances measured toward different star-forming environments (high-mass versus low-mass, Galactic center versus Galactic disk) reveal a remarkable similarity, an indication that the underlying chemistry is relatively independent of variations in their physical conditions. Studies of molecular isotopologs in star-forming regions provide a link with measurements in our own Solar System, and thus may shed light on the chemical similarities and differences expected in other planetary systems.Comment: Invited review to be published in Annual Reviews of Astronomy and Astrophysics; 55 pages, 10 figure

Terahertz gas phase spectroscopy using a high finesse Fabry-P\'erot cavity

The achievable instrument sensitivity is a critical parameter for the continued development of THz applications. Techniques such as Cavity-Enhanced Techniques and Cavity Ring Down Spectroscopy have not yet been employed at THz frequency due to the difficulties to construct a high finesse Fabry-P\'erot cavity. Here, we describe such a THz resonator based on a low-loss oversized corrugated waveguide with highly reflective photonic mirrors obtaining a finesse above 3000 around 620 GHz. These components enable a Fabry-Perot THz Absorption Spectrometer with an equivalent interaction length of one kilometer giving access to line intensities as low as 10-27cm- 1/(molecule/cm2) with a S/N ratio of 3. In addition, the intracavity optical power have allowed the Lamb-Dip effect to be studied with a low-power emitter, an absolute frequency accuracy better than 5 kHz can be easily obtained providing an additional solution for rotational spectroscopy.Comment: 7 pages, 4 figure

Using the event calculus to reason about problem diagrams

Central to the problem frames approach is the distinction of three different descriptions: requirements R, domain assumptions W and specifications S, tied together with the so-called 'frame concern', a proof obligation that has to hold between them if a problem diagram is to be correct: S, W |- R. The form this proof should take is not fixed a priori. It might, however, be desirable to automate it in order to allow for an efficient analysis of large diagrams. To make this possible, we follow some earlier suggestions to use the Event Calculus as a suitable formalism for these descriptions. The main contribution of the present paper is a set of consistency rules as well as guidelines for passing from a problem diagram to its formal description

Coupled experiment/simulation approach for the design of radiation-hardened rare-earth doped optical fibers and amplifiers

We developed an approach to design radiation-hardened rare earth -doped fibers and amplifiers. This methodology combines testing experiments on these devices with particle swarm optimization (PSO) calculations. The composition of Er/Yb-doped phosphosilicate fibers was improved by introducing Cerium inside their cores. Such composition strongly reduces the amplifier radiation sensitivity, limiting its degradation: we observed a gain decreasing from 19 dB to 18 dB after 50 krad whereas previous studies reported higher degradations up to 0°dB at such doses. PSO calculations, taking only into account the radiation effects on the absorption efficiency around the pump and emission wavelengths, correctly reproduce the general trends of experimental results. This calculation tool has been used to study the influence of the amplifier design on its radiation response. The fiber length used to ensure the optimal amplification before irradiation may be rather defined and adjusted to optimize the amplifier performance over the whole space mission profile rather than before integration in the harsh environments. Both forward and backward pumping schemes lead to the same kind of degradation with our active fibers. By using this promising coupled approach, radiation-hardened amplifiers nearly insensitive to radiations may be designed in the future

Aged Nicotinamide Riboside Kinase 2 Deficient Mice Present an Altered Response to Endurance Exercise Training

Background: Skeletal muscle aging is marked by the development of a sarcopenic phenotype, a global decline of muscle energetic capacities, and an intolerance to exercise. Among the metabolic disorders involved in this syndrome, NAD metabolism was shown to be altered in skeletalmuscle, with an important role for the NAMPT enzyme recycling the nicotinamide precursor. An alternative pathway for NAD biosynthesis has been described for the nicotinamide riboside vitamin B3 precursor used by the NMRK kinases, including the striated muscle-specific NMRK2.Aim: With this study, our goal is to explore the ability of 16-month-old Nmrk2−/− mice to perform endurance exercise and study the consequences on muscle adaptation to exercise.Methods: 10 control and 6 Nmrk2−/− mice were used and randomly assigned to sedentary and treadmill endurance training groups. After 9 weeks of training, heart and skeletal muscle samples were harvested and used for gene expression analysis, NAD levels measurements and immunohistochemistry staining.Results: Endurance training triggered a reduction in the expression of Cpt1b and AcadL genes involved in fatty acid catabolism in the heart of Nmrk2−/− mice, not in control mice. NAD levels were not altered in heart or skeletal muscle, nor at baseline neither after exercise training in any group. Myh7 gene encoding for the slow MHC-I was more strongly induced by exercise in Nmrk2−/− mice than in controls. Moreover, IL-15 expression levels is higher in Nmrk2−/− mice skeletal muscle at baseline compared to controls. No fiber type switch was observed in plantaris after exercise, but fast fibers diameter was reduced in aged control mice, not in Nmrk2−/− mice. No fiber type switch or diameter modification was observed in soleus muscle.Conclusion: In this study, we demonstrated for the first time a phenotype in old Nmrk2−/− mice in response to endurance exercise training. Although NMRK2 seems to be predominantly dispensable to maintain global NAD levels in heart and skeletal muscle, we demonstrated a maladaptive metabolic response to exercise in cardiac and skeletal muscle, showing that NMRK2 has a specific and restricted role in NAD signaling compared to the NAMPT pathway