Results 1 - 10 of 13634
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[en] Competition between three-photon resonantly enhanced vacuum ultraviolet third-harmonic generation and six-photon multiphoton ionization using the A state in gaseous carbon monoxide is observed. Excitation spectra of the third-harmonic emission exhibit increasing blue shifts and broadening with increasing pressure due to the phase matching requirements. Estimates for the efficiency and tunability show that third-harmonic generation in carbon monoxide molecules is a promising source for coherent vacuum ultraviolet light
[en] A continuous wave CO laser was used to excite the vibrational mode of CO in gas mixtures. 13C isotope enrichment was studied. High steady-state excitation of the CO vibrational mode (0.3 eV/molecule) was achieved, while a translational-rotational temperature near 3000K was maintained by the steady flow of cold gas into the cell. Kinetics of the observed C2 formation were studied. Diagnostic experiments were begun to detect reaction intermediates in the enrichment process
[en] Endogenous carbon monoxide (CO), which is produced by the enzyme heme oxygenase (HO), participates as a neuromodulator in physiological processes such as thermoregulation and nociception by stimulating the formation of 3′,5′-cyclic guanosine monophosphate (cGMP). In particular, the acute physical restraint-induced fever of rats can be blocked by inhibiting the enzyme HO. A previous study reported that the HO-CO-cGMP pathway plays a key phasic antinociceptive role in modulating noninflammatory acute pain. Thus, this study evaluated the involvement of the HO-CO-cGMP pathway in antinociception induced by acute stress in male Wistar rats (250-300 g; n=8/group) using the analgesia index (AI) in the tail flick test. The results showed that antinociception induced by acute stress was not dependent on the HO-CO-cGMP pathway, as neither treatment with the HO inhibitor ZnDBPG nor heme-lysinate altered the AI. However, antinociception was dependent on cGMP activity because pretreatment with the guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxaline-1-one (ODQ) blocked the increase in the AI induced by acute stress
[en] Experimental facilities and tests are described for the investigation of the energy, temporal, and spectral characteristics of the emission of pulsed high-pressure CO lasers excited by the electron-beam-controlled discharge method, with emission energy up to 400 J and efficiency up to 35%, and with an excitation volume of 5 liters. The dependences of the output parameters of such lasers on the excitation power and duration, as well as on the composition and density of the working gas mixture, are investigated. It is shown that the results of numerical calculations of the parameters of pulsed electron-beam CO lasers agree qualitatively with the experimental data. The greatest discrepancies are observed for a laser with an uncooled gas mixture and for a pure carbon monoxide laser
[en] The influence of a multi-line CO laser focusing on spectral characteristics of broadband sum-frequency generation in ZnGeP2 nonlinear crystal was experimentally and numerically studied. Maximal frequency conversion was experimentally observed under a tight focusing laser beam of a multi-line CO laser rather than a single-line one. The tight focusing resulted in a broadening sum-frequency generation spectrum and an increasing total, i.e. integrated over the spectrum, frequency conversion efficiency. These effects were due to the increasing phase-matching bandwidth and angular dispersion. The maximal conversion efficiency of the multi-line CO laser was numerically demonstrated to take place at a focal length of 0.4 times that required for the single-line one. (letter)
[en] We report the detection of molecular CO(1-0) gas in the high-z radio galaxy MRC 0152-209 (z = 1.92) with the Australia Telescope Compact Array Broadband Backend (ATCA/CABB). This is the third known detection of CO(1-0) in a high-z radio galaxy to date. CO(1-0) is the most robust tracer of the overall molecular gas content (including the widespread, low-density, and sub-thermally excited component), hence observations of CO(1-0) are crucial for studying galaxy evolution in the early universe. We derive L'CO = 6.6 ± 2.0 x 1010 K km s-1 pc2 for MRC 0152-209, which is comparable to that derived from CO(1-0) observations of several high-z submillimeter and star-forming BzK galaxies. The CO(1-0) traces a total molecular hydrogen mass of MH2 = 5 x 1010 (αx/0.8) Msun. MRC 0152-209 is an infrared bright radio galaxy, in which a large reservoir of cold molecular gas has not (yet) been depleted by star formation or radio source feedback. Its compact radio source is reliably detected at 40 GHz and has a steep spectral index of α = -1.3 between 1.4 and 40 GHz (4-115 GHz in the galaxy's rest frame). MRC 0152-209 is part of an ongoing systematic ATCA/CABB survey of CO(1-0) in high-z radio galaxies between 1.7 < z < 3.
[en] Carbon monoxide observations of neutral matter near W3 provide an excellent example of the formative process of 0 stars. As in other regions where O stars are forming the young stars in W3 are located in dense cloud fragments that are at the edge of an extended molecular cloud complex. This peculiar formation site is simply explained in terms of a million year old shock that probably surrounds the expanding H II region IC1805. The contrast between this situation for W3 and what is found in other star-forming regions where only low mass stars occur is emphasized. (Auth.)
[en] We report the detection of the 12CO J = 1-0 emission line in [H89]1821+643, one of the most optically luminous quasi-stellar objects (QSOs) in the local universe, and a template ULIRG-to-QSO transition object, located in a rich, cool-core cluster at z = 0.297. The CO emission is likely to be extended, highly asymmetric with respect to the center of the host elliptical where the QSO resides, and correspond with a molecular gas mass of ∼8.0 x 109 Msun. The dynamical mass enclosed by the CO emission-line region could amount to ∼1.7 x 1012 Msun (80% of the total mass of the elliptical host). The bulk of the CO emission is located at ∼9 kpc southeast from the nuclei position, close to a faint optical structure, suggesting that the CO emission could either represent a gas-rich companion galaxy merging with the elliptical host or a tail-like structure reminiscent of a previous interaction. We argue that the first scenario is more likely given the large masses implied by the CO source, which would imply a highly asymmetric elliptical host. The close alignment between the CO emission's major axis and the radio plume suggests a possible role in the excitation of the ambient gas reservoir by the latter. The stacking technique was used to search for CO emission and 3-mm continuum emission from galaxies in the surrounding cluster. However, no detection was found toward individual galaxies or the stacked ensemble of galaxies, with a 3σ limit of <1.1 x 109 Msun for the molecular gas.
[en] This study was undertaken to investigate the effect of chromium on the reduction behaviour of ferric oxide with carbon monoxide (10 %, v/v) in nitrogen as a reductant. Ferric oxide was impregnated with 3 % chromium to produce chromium-doped ferric oxide (Cr-Fe2O3). The reduction behaviour and the kinetic studies of Cr-Fe2O3 and Fe2O3 have been studied by temperature programmed reduction (TPR) and the phases formed of partially and completely reduced samples were characterized by X-ray diffraction spectroscopy (XRD). Meanwhile, the activation energy values were calculated from the Arrhenius equation using Wimmer's method. TPR results indicate that the reduction of Cr-Fe2O3 proceeded in two reduction steps (Fe2O3→Fe3O4→Fe), while, Fe2O3 proceeded in three reduction steps (Fe2O3→Fe3O4→FeO→Fe) with doped ferric oxide showed a large shifted towards lower temperature. The complete reduction of ferric oxide to metallic Fe occur at 700 degree Celcius compared to the undoped ferric oxide (900 degree Celcius). The XRD pattern showed that the diffraction peaks of Cr-Fe2O3 are more intense compare to Fe2O3, indicating that the improvement on the crystallinity of the characteristic peaks of Fe2O3 with no additional peak observed meaning that the chromium particles loaded on the ferric oxide were well dispersed. Furthermore, additional of 3 % chromium on ferric oxide gives larger surface area and decrease in the activation energy up to 12.39 % regarding to transition phases of Fe2O3→Fe3O4 during the reduction process may also led to the increase in the rates of ferric oxide reduction. (author)