Astronomical identification of CN-, the smallest observed molecular anion

We present the first astronomical detection of a diatomic negative ion, the cyanide anion CN-, as well as quantum mechanical calculations of the excitation of this anion through collisions with para-H2. CN- is identified through the observation of the J = 2-1 and J = 3-2 rotational transitions in the C-star envelope IRC +10216 with the IRAM 30-m telescope. The U-shaped line profiles indicate that CN-, like the large anion C6H-, is formed in the outer regions of the envelope. Chemical and excitation model calculations suggest that this species forms from the reaction of large carbon anions with N atoms, rather than from the radiative attachment of an electron to CN, as is the case for large molecular anions. The unexpectedly large abundance derived for CN-, 0.25 % relative to CN, makes likely its detection in other astronomical sources. A parallel search for the small anion C2H- remains so far unconclusive, despite the previous tentative identification of the J = 1-0 rotational transition. The abundance of C2H- in IRC +10216 is found to be vanishingly small, < 0.0014 % relative to C2H.Comment: 5 pages, 4 figures; accepted for publication in A&A Letter

Search for anions in molecular sources: C4H- detection in L1527

We present the results of a search for the negative ion C4H- in various dark clouds, low mass star-forming regions and photon-dominated regions (PDRs). We have also searched for C6H-, C2H- and CN- in some of the sources. The millimeter-wave observations were carried out with the IRAM-30m telescope. We detect C4H-, through the J = 9-8 and J = 10-9 rotational transitions, in the low mass star-forming region L1527. We thus confirm the tentative detection of the J = 9-8 line recently reported toward this source. The [C4H-]/[C4H] ratio found is 0.011 %, which is slightly lower than the value observed in IRC +10216, 0.024 %, but above the 3 sigma upper limit we derive in TMC-1, < 0.0052 %. We have also derived an upper limit for the [C6H-]/[C6H] ratio in the Horsehead Nebula, and for various anion-to-neutral ratios in the observed sources. These results are compared with recent chemical models.Comment: 4 pages, 1 figure; accepted for A&A Letter

Krafla magma testbed: Understanding and using the magma-hydrothermal connection

The Krafla Magma Testbed (KMT), Krafla Caldera, Iceland, is proposed to be the first magma observatory, an international multi-borehole facility where teams will conduct scientific experiments and engineering tests focused on the magma-hydrothermal interface in a superhot geothermal systems (SHGS). Objectives are to: 1) Core and monitor from the roots of the hydrothermal system to the top of the magma body; 2) Provide ground-truth testing of surface-based techniques for locating magma; 3) Perturb the deep system to understand signals interpreted as volcano “unrest”; 4) Advance drilling and completion technology so that superhot and supercritical fluids can be produced from the magma roof zone; and 5) Advance sensor technology so that magma bodies can be monitored directly, vastly improving the eruption warnings important to 10% of Earth's population. KMT will provide a vanguard view of magma and hydrothermal circulation as the single system that it is. It will integrate the separate communities of practice of geothermal energy, which relies heavily on direct drilling observations; and volcanology, which relies on surface observations and theoretical models. The driving force is that geothermal drilling hit magma in Iceland, Kenya, and Hawaii, revealing how close to the surface magma exists and how closely connected magma is to the hydrothermal system. KMT is a 3 rd path in efforts to expand geothermal use. One path is to go deeper in cooler places, the Enhanced Geothermal System (EGS) concept, relying on advances in drilling and reservoir stimulation for economic viability, e.g. Frontier Observatory for Research in Geothermal Energy (FORGE) of the U.S. Department of Energy. Another, within SHGS, is to drill to conditions where fluids should be supercritical, e.g. IDDP-2 of Iceland Deep Drilling Program (IDDP) at Reykjanes. The 3 rd , also SHGS and pursued by KMT, is to access the vicinity of a magma body. This takes advantage of magma's high energy density due to latent heat of crystallization and delivered by convection to sustain high power output. Not only have SHGS wells proximal to magma at Krafla Caldera, Iceland, exhibited high flow rates equivalent to >100 MWt, but the expected efficiency of conversion to electricity is ~30% vs. ~10% for conventional geothermal. When combined with the new efficiencies of High Voltage Direct Current (HVDC) tranmission, the economic balance could shift from low-grade geothermal sources near the consumer to high-grade sources farther from the consumer

Germinação e vigor de sementes de trigo inoculadas com Azospirillum brasilense.

Editores técnicos: Joseani Mesquita Antunes, Ana Lídia Variani Bonato, Márcia Barrocas Moreira Pimentel

Negative Ions in Space

Until a decade ago, the only anion observed to play a prominent role in astrophysics was H–. The bound–free transitions in H– dominate the visible opacity in stars with photospheric temperatures less than 7000 K, including the Sun. The H– anion is also believed to have been critical to the formation of molecular hydrogen in the very early evolution of the Universe. Once H₂ formed, about 500 000 years after the Big Bang, the expanding gas was able to lose internal gravitational energy and collapse to form stellar objects and “protogalaxies”, allowing the creation of heavier elements such as C, N, and O through nucleosynthesis. Although astronomers had considered some processes through which anions might form in interstellar clouds and circumstellar envelopes, including the important role that polycyclic aromatic hydrocarbons might play in this, it was the detection in 2006 of rotational line emission from C₆H– that galvanized a systematic study of the abundance, distribution, and chemistry of anions in the interstellar medium. In 2007, the Cassini mission reported the unexpected detection of anions with mass-to-charge ratios of up to ˜10 000 in the upper atmosphere of Titan; this observation likewise instigated the study of fundamental chemical processes involving negative ions among planetary scientists. In this article, we review the observations of anions in interstellar clouds, circumstellar envelopes, Titan, and cometary comae. We then discuss a number of processes by which anions can be created and destroyed in these environments. The derivation of accurate rate coefficients for these processes is an essential input for the chemical kinetic modeling that is necessary to fully extract physics from the observational data. We discuss such models, along with their successes and failings, and finish with an outlook on the future

Maximum tumor diameter is not an independent prognostic factor in high-risk localized prostate cancer

Contains fulltext : 69173.pdf (publisher's version ) (Closed access)OBJECTIVES: Previous studies suggest that maximum tumor diameter (MTD) is a predictor of recurrence in prostate cancer (PC). This study investigates the prognostic value of MTD for biochemical recurrence (BCR) in patients with PC, after radical prostatectomy (RP), with emphasis on high-risk localized prostate cancer. METHODS: RP specimens of 542 patients were evaluated with a median follow-up of 39.5 months (range 0.6-150 months). MTD was defined as the largest diameter of the largest tumor; high-risk as >or=T2c or PSA level>20 ng/ml or Gleason score>or=8 and BCR as two consecutive PSA levels>0.10 ng/ml. Proportional hazards multivariable regression models were composed to determine prognostic factors for BCR. RESULTS: Overall, 114 patients developed BCR after RP. The overall 5-year risk of BCR was 25% (95% CI=20.4-29.6), and median MTD was 24 mm (range 1-65). MTD in the total and high-risk group was associated with total tumor volume, volume of the largest tumor, pre-operative PSA levels, and Gleason score. In a univariable analyses, MTD was weakly associated with risk of BCR (HR=1.02 per mm increase, 95% CI=1.002-1.035, P=0.024) in the total group; in the high-risk group this association was lost (HR=1.01, 95%CI=0.99-1.03, P=0.18). Multivariable analyses indicated that positive surgical margins, higher Gleason score, advanced pathological stage, and multiple tumors were the main prognostic factors for BCR irrespective of the risk profile. MTD did not provide additional information. CONCLUSIONS: MTD is not an independent prognostic factor for BCR in patients treated with RP, irrespective of the risk profile