On the non-linear relationships between N(CaII), N(KI) and N(H)

Calculations by Penstonet al. (1969) of the mass distribution of interstellar clouds are reexamined in the light of Hobbs's data on the relationship between N(Caii) and N(H). The mass spectrum is calculated using two different sets of simple assumptions. Two possible explanations of the quadratic dependence of N(Ki) on N(H) are briefly examined.     

Search for spatial variation in the jovian N/N ratio from Cassini/CIRS observations

We have used the spectra obtained by the Composite Infrared Spectrometer (CIRS) onboard the Cassini spacecraft to search for latitudinal variation in the ¹⁵N/¹⁴N ratio on Jupiter. We found no variations statistically significant given the observational and model uncertainties. The absence of latitudinal variations demonstrates that ¹⁵NH₃ is not fractionated in Jupiter's atmosphere, and that the measured ¹⁵N/¹⁴N represents Jupiter's global value. Our mean value for the global jovian ¹⁵N/¹⁴N ratio of (2.22±0.52)×10⁻³ agrees with previous measurements made by Fouchet et al. (2000, Icarus 143, 223-243) and Owen et al. (2001, Astrophys. J. 553, L77-L79). We argue that the jovian isotopic ¹⁵N/¹⁴N ratio must represent the solar nitrogen isotopic composition. The solar ¹⁵N/¹⁴N ratio hence significantly differs from the terrestrial value: (¹⁵N/¹⁴N)_⊕=3.68×10⁻³. This supports the proposition that terrestrial nitrogen originates from a nitrogen reservoir isolated from the main nitrogen reservoir in the proto-solar nebula. The origin and carrier of this isolated reservoir are still unknown.     

Diurnal variability of thermospheric N and NO

A model for diurnal variations of neutral and ionic nitrogen compounds in the thermosphere is reconstructed on the basis of a new photochemical aspect on N(²D), together with new observations of the NO density. The NO density so far measured must be reduced by a factor 2, due to a revision of the fluorescence coefficient for the NO γ-band airglow. Incorporating the quenching reaction of N(²D) with O in the model calculation results in a reduction of the NO density at heights as low as 100 km. These two effects are combined to lead to an evaluation that the N(²D) quantum yield for various possible reactions is as large as 0.9. A smaller rate coefficient for the quenching reaction than that measured in the laboratory, i.e. 1.0 × 10^?12cm³sec^?1 is favourable for the recent NO observation in the early morning, as well as the observed emission rates of the 5200 A airglow from N(²D) The present model predicts a significant day-to-night variation of N and NO densities at heights above 100 km. Below 100 km, the NO density is fairly stable because of its long chemical time constant. Since the rate coefficient for the conversion of N(⁴S) to NO is highly temperature dependent, the relative population of N(⁴S) and NO is very sensitive to the thermospheric temperature variation. Large variations of both N(⁴S) and NO densities due to the temperature change could occur especially at night. The model is in good agreement with the NO observations so far available in low and middle latitudes, as well as the N observation by the use of a rocket in the twilight.     

The Titan N/N and C/C isotopic ratios in HCN from Cassini/CIRS

We report the detection of H¹³CN and HC¹⁵N in mid-infrared spectra recorded by the Composite Infrared Spectrometer (CIRS) aboard Cassini, along with the determination of the ¹²C/¹³C and ¹⁴N/¹⁵N isotopic ratios. We analyzed two sets of limb spectra recorded near 13-15° S (Tb flyby) and 83° N (T4 flyby) at 0.5 cm⁻¹ resolution. The spectral range 1210-1310 cm⁻¹ was used to retrieve the temperature profile in the range 145-490 km at 13° S and 165-300 km at 83° N. These two temperature profiles were then incorporated in the atmospheric model to retrieve the abundance profile of H¹²C¹⁴N, H¹³CN and HC¹⁵N from their bands at 713, 706 and 711 cm⁻¹, respectively. The HCN abundance profile was retrieved in the range 90-460 km at 15° S and 165-305 km at 83° N. There is no evidence for vertical variations of the isotopic ratios. Constraining the isotopic abundance profiles to be proportional to the HCN one, we find at 15° S, and at 83° N, two values that are statistically consistent. A combination of these results yields a ¹²C/¹³C value equal to 75±12. This global result, as well as the 15° S one, envelop the value in Titan's methane (82.3±1) [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779-784] measured at 10° S and is slightly lower than the terrestrial inorganic standard value (89). The ¹⁴N/¹⁵N isotopic ratio is found equal to at 15° S and at 83° N. Combining the two values yields ¹⁴N/¹⁵N = 56 ± 8, which corresponds to an enrichment in ¹⁵N of about 4.9 compared with the terrestrial ratio. These results agree with the values obtained from previous ground-based millimeter observations [Hidayat, T., Marten, A., Bézard, B., Gautier, D., Owen, T., Matthews, H.E., Paubert, G., 1997. Icarus 126, 170-182; Marten, A., Hidayat, T., Biraud, Y., Moreno, R., 2002. Icarus 158, 532-544]. The ¹⁵N/¹⁴N ratio found in HCN is ∼3 times higher than in N₂ [Niemann, H.B., and 17 colleagues, 2005. Nature 438, 779-784], which implies a large fractionation process in the HCN photochemistry.     

Temperature dependence of HC3N,C6H2, and C4N2 mid-UV absorption coefficients. Application to the interpretation of Titan's atmospheric spectra

Three organic compounds (HC₃N, C₆H₂, and C₄N₂) relevant of Titan's atmosphere have been studied within the framework of the SIPAT (Spectroscopie UV d'Intérêt Prébiologique dans l'Atmosphère de Titan) program. Since this facility is still unable to reach the very low temperatures (170 K) of Titan's high atmosphere, spectra have to be obtained at several absorption-cell temperatures, and the data extrapolated towards lower temperatures. Previously published HC₃N and C₆H₂ absorption coefficient data are reviewed, while new spectroscopic data are presented on C₄N₂. Integrated intensity calculations over the vibrational bands are performed apart from the background continuum. Thus, only the band contrast is considered here. While, the temperature dependence of the hot-band integrated intensity follows a Boltzmann distribution, we have enhanced the fit through an empirical parametrisation to account for the observed temperature dependence of the C₄N₂ and HC₃N absorption coefficients, and to extrapolate those data to the low temperature conditions of Titan's high atmosphere. Finally, we discuss the implications of the results to possible detection by remote sensing observations of these minor compounds in Titan's atmosphere.     

New light on the search for low-metallicity galaxies – I. The N2 calibrator

We present a simple metallicity estimator based on the logarithmic [N  ii ]   λ 6584/H α   ratio, hereafter N2, which we envisage will become very useful for ranking galaxies in a metallicity sequence from redshift survey-quality data even for moderately low spectral resolution.
We have calibrated the N2 estimator using a compilation of H  ii galaxies having accurate oxygen abundances, plus photoionization models covering a wide range of abundances. The comparison of models and observations indicates that both primary and secondary nitrogen are important for the relevant range of metallicities.
The N2 estimator follows a linear relation with log(O/H) that holds for the whole abundance range covered by the sample, from approximately  1/50th  to twice the Solar value  [7.2<12+log(O/H)<9.1]  . We suggest that the ([S  ii ]   λλ 6717,6731/H α )  ratio (hereafter S2) can also be used as a rough metallicity indicator. Because of its large scatter the S2 estimator will be useful only in systems with very low metallicity, where [N  ii ] λ 6584 is not detected or in low-resolution spectra where [N  ii ] λ 6584 is blended with H α .     

Bifurcation of central configuration in the 2N+1 body problem

The bifurcation of central configuration in the Newtonian N-body problem for any odd number N ≥ 7 is shown. We study a special case where 2n particles of mass m on the vertices of two different coplanar and concentric regular n-gons (rosette configuration) and an additional particle of mass m₀ at the center are governed by the gravitational law he 2n+1 body problem. This system is of two degrees of freedom and permits only one mass parameter μ =m ₀/m. This parameter μ controls the bifurcation. If n≥ 3, namely any odd N ≥ 7, then the number of central configurations is three when μ ≥ μ _c , and one when μ ≥ μ _c . By combining the results of the preceding studies and our main theorem, explicit examples of bifurcating central configuration are obtained for N ≤ 13, for any odd N ∈ [15,943], and for any N ≥ 945.     

Mass spectrometric study of three-body ion-molecule clustering reactions of CpHq+ ions with N2 or CH4 in N2-CH4 mixtures

Thermochemical data for several ion-molecule clustering of hydrocarbon ions with N2 or CH4 were obtained from clustering equilibria studies in gas mixtures irradiated by alpha-particles. High-pressure mass spectrometry was used to determine the enthalpy and entropy changes of clustering (delta H0 and delta S0, respectively) for the reactions X+(N2)n-1 + 2N2 <==> X(+)(N2)n + N2 with X = CH5, n = 1-2; X = C2H5, n = 1-4; and X = C3H7, n = 1. For X = CH5, the values (delta H0; delta S0) are found to be (-6.8 kcal mol-1; -19.7 cal mol-1 K-1) for n = 1, and (-5.3 kcal mol-1; -15.9 cal mol-1 K-1) for n = 2. For X = C2H5, (delta H0; delta S0) = (-6.9 kcal mol-1; -18.2 cal mol-1 K-1), for n = 1, and (-4.6 kcal mol-1; -20.8 cal mol-1 K-1) for n = 2. From the equilibrium measurements at 129 K, estimates of the thermochemical values could be obtained for n = 3-4. The results obtained for the free energy, delta G0, were -1.4 kcal mol-1 for n = 3, and -1.1 kcal mol-1 for n = 4. For X = C3H7 we found delta G0 = -0.7 kcal mol-1 at 213 K. The association reactions X+ + 2CH4 <==> X+(CH4) + CH4 with X = CH5, C2H5, C2H7, and C3H7 were also studied, resulting in free energy values at 206 K of -3.1, -1.9, -0.5 and -1.3 kcal mol-1, respectively. The results for CH5, C2H5 and C3H7 are compared with previously reported measurements.     

Decametric N Burst: A Consequence of the Interaction of Two Coronal Mass Ejections

Radio emissions of electron beams in the solar corona and interplanetary space are tracers of the underlying magnetic configuration and of its evolution. We analyse radio observations from the Culgoora and WIND/WAVES spectrographs, in combination with SOHO/LASCO and SOHO/MDI data, to understand the origin of a type N burst originating from NOAA AR 10540 on January 20, 2004, and its relationship with type II and type III emissions. All bursts are related to the flares and the CME analysed in a previous paper (Goff et al., 2007). A very unusual feature of this event was a decametric type N burst, where a type III-like burst, drifting towards low frequencies (negative drift), changes drift first to positive, then again to negative. At metre wavelengths, i.e., heliocentric distances ≲1.5R _⊙, these bursts are ascribed to electron beams bouncing in a closed loop. Neither U nor N bursts are expected at decametric wavelengths because closed quasi-static loops are not thought to extend to distances ≫1.5R _⊙. We take the opportunity of the good multi-instrument coverage of this event to analyse the origin of type N bursts in the high corona. Reconnection of the expanding ejecta with the magnetic structure of a previous CME, launched about 8 hours earlier, injects electrons in the same manner as with type III bursts but into open field lines having a local dip and apex. The latter shape was created by magnetic reconnection between the expanding CME and neighbouring (open) streamer field lines. This particular flux tube shape in the high corona, between 5R _⊙ and 10R _⊙, explains the observed type N burst. Since the required magnetic configuration is only a transient phenomenon formed by reconnection, severe timing and topological constraints are present to form the observed decametric N burst. They are therefore expected to be rare features.     

The development of the scientific and design school of G.N. Babakin during the creation of deep-space automated spacecraft

This article presents the main outline of the creation of the scientific and design school of G.N. Babakin, who was a corresponding member of the Academy of Sciences of the USSR, during the creation of automated spacecraft for fundamental space research.     

On nova Scorpii 2007 N.1 (V1280 Sco)

We present the results of our photometric and spectroscopic observations of Nova Sco 2007 N.1 (V1280 Sco). The photometric data was represented by a single data point in the light curve since the observation was carried out only for one night. The spectra cover two different phases of the object’s evolution during the outburst, i.e. pre-maximum and post-maximum. Measurements of the P-Cygni profile on Na I ‘D’ line (5889 Å) was derived as the velocity of shell expansion, yielding 1567.43±174.14 km s^?1. We conclude that V1280 Sco is a fast Fe II-type nova.     

Bursts of type N in Jupiter's decametric radio spectra

Dynamic spectra of Jupiter's decametric emission often display narrow-band features, referred to as events of type N (Carr et al., 1983). The average bandwidth of these emissions is in the vicinity of 200 kHz, their durations are typically in the decasecond range, and their f-t slopes are small and random. Although the N-bursts can be described as narrow-band L-bursts, it seems that they are realted to S-bursts in their area of occurrence in the Io-B region, the durations of the emission envelopes, and their bandwidths. Possible implications are discussed.     

Abundances and radial gradients from disk planetary nebulae: He,N, C,and Cl

Chemical abundances of the elements He, N, C, and Cl are presented for disk planetary nebulae, comprising Peimbert types I, II, and III. Average abundances for these classes are determined and compared with the remaining abundances available. The presence of abundance gradients relative to hydrogen for disk nebulae is investigated in a region of about 8 kpc centered in the solar system. It can be concluded that the gradients of the ratios N/H, Cl/H, and probably C/H are similar to the O/H gradient, especially for type II objects.     

A simulation study on the eco-environmental effects of 3N Shelterbelt in North China

Based on the Global Land Cover Characteristics Database (GLCCD) generated by the U.S. Geological Survey (USGS) and University of Nebraska-Lincoln (UNL), a new land cover dataset within a domain of 14.1–49.6°N, 84.6–140.5°E is extracted. This dataset is used to identify the achievements of constructing 3N (Northeast, North and Northwest of China) Shelterbelt in North China and to update the lower boundary conditions of the mesoscale model (MM5), a widely used mesoscale meteorological model. The model is then used to simulate the regional climate effects of the 3N Shelterbelt, the largest forestation engineering in the world. The simulation shows that the construction of the 3N Shelterbelt and the corresponding land use and land cover (LULC) variations in China have changed the roughness length in the cited model domain significantly. Consequently, the surface layer wind speed, air temperature, humidity, and the precipitation are all changed. As compared with the control run without the 3N Shelterbelt, the regional climate in North China is improved shown by the decreased wind speed, increased air humidity and precipitation. The paper also stresses that, in meteorological or climatic simulations, the lower boundary conditions related to the land cover has to be updated frequently by the satellite observed database since the LULC vary fast due to the increasing world population and human activities, this is especially true in developing countries like China.     

Measurements in N2-CH4(C2H2) discharges of reaction rates and thermochemical constants for Titan atmosphere study

The kinetic reactions in N2-xCH4(C2H2) gas discharges with x less than 1% have been studied by emission spectroscopy in the afterglow of D.C. discharges and by mass spectroscopy from radiolysis ionization using alpha particles. The pressure range is from several Torr to 100 Torr. At the end of N2 D.C. discharges at room temperature, for a residence time of about 10(-2) s, the dominant active species are the N atoms with density of 10(14)-10(15) cm-3 for N2 density of about 10(17) cm-3 (3 Torr), the N2(X,V) vibrational molecules with for example [N2(X,V = 10)] approximately 10(14) cm-3 and the electronic metastable molecules N2(A 3 sigma u +) with a density of 10(12) cm-3. In such conditions, the following kinetic reactions have been studied: N2(A) + N2(A) --> N2(C,B,V') + N2(X), N2(A) + N2(X,V>5) --> N2(X) + N2(B,V') in pure N2 post-discharges and N2(A) + CH4 --> products, C + N + M2 --> CN(B,V') + M2, N2(X,V>4) + CN --> N2(X) + CN(B,A,V'), in N2-1% CH4 post-discharges. The clustering reactions of N2-(1-5%)CH4(C2H2) gas mixtures after radiolysis ionization have been studied for the H2CN+ nN2 ions and the equilibrium constants have been determined in the temperature range T = 140-300 K.     

The European Large Area ISO Survey: optical identifications of 15-μm and 1.4-GHz sources in N1 and N2

We present the multiwavelength properties and catalogue of the 15 μm and 1.4 GHz radio sources detected in the European Large Area ISO Survey ( ELAIS ) areas N1 and N2. Using the optical data from the Wide Field Survey we use a likelihood ratio method to search for the counterparts of the 1056 and 691 sources detected at 15 μm and 1.4 GHz, respectively, down to flux limits of   S ₁₅= 0.5 mJy  and   S _1.4 GHz= 0.135 mJy  . We find that ∼92 per cent of the 15 μm ELAIS sources have an optical counterpart down to   r '= 24  . All mid-infrared (IR) sources with fluxes   S ₁₅≥ 3 mJy  have an optical counterpart. The magnitude distribution of the sources shows a well-defined peak at relatively bright magnitudes   r '∼ 18  . The mid-IR-to-optical and radio-to-optical flux diagrams are presented and discussed in terms of actual galaxy models. About 15 per cent of the sources are bright galactic stars; of the extragalactic objects ∼65 per cent are compatible with being normal or starburst galaxies and ∼25 per cent active galactic nuclei (AGNs). Objects with mid-IR-to-optical fluxes larger than 100 are found, comprising ∼20 per cent of the sample. We suggest that that these sources are highly obscured luminous and ultraluminous starburst galaxies and AGNs.     

Transition probabilities for N IV,O V and O VI

Dipole lengths and dipole velocities have been determined for a series of transitions in N IV, O V and O VI. Some of these transitions are of astrophysical interest and the remainder were computed to give a more complete picture of the transitions in the respective ions. With the dipole length and dipole velocity known the line strengths and, therefore, the transition probabilities can be readily obtained. Agreement between dipole length and dipole velocity has been obtained in most cases.     

In situ survey of graphite in unequilibrated chondrites: Morphologies,C, N,O, and H isotopic ratios

Abstract— We performed in situ morphological and isotopic studies of graphite in the primitive chondrites Khohar (L3), Mezö‐Madaras (L3), Inman (L3), Grady (H3), Acfer 182 (CH3), Acfer 207 (CH3), Acfer 214 (CH3), and St. Marks (EH5). Various graphite morphologies were identified, including book, veins, fibrous, fine‐grained, spherulitic, and granular graphite, and cliftonite. SIMS measurements of H, C, N, and O isotopic compositions of the graphites revealed large variations in the isotopic ratios of these four elements. The δ¹⁵N and δ¹³C values show significant variations among the different graphite types without displaying any strict correlation between the isotopic composition and morphology. In the Khohar vein graphites, large ¹⁵N excesses are found, with δ¹⁵N_max ～+955‰, confirming previous results. Excesses in ¹⁵N are also detected in fine‐grained graphites in chondrites of the CH clan, Acfer 182, Acfer 207, and Acfer 214, with δ¹⁵N ranging up to +440‰. The ¹⁵N excesses are attributed to ion‐molecule reactions at low temperatures in the interstellar molecular cloud (IMC) from which the solar system formed, though the largest excesses seem to be incompatible with the results of some recent calculation. Significant variations in the carbon isotopic ratios are detected between graphite from different chondrite groups, with a tendency for a systematic increase in δ¹³C from ordinary to enstatite to carbonaceous chondrites. These variations are interpreted as being due to small‐ and large‐scale carbon isotopic variations in the solar nebula.     

Microwave bursts from Jupiter due to K, N, P2 and S fragments

This article reports the observations of microwave emission from Jupiter during the impact of K, N, P2 and S fragments of the comet Shoemaker-Levy 9. The comparison of microwave bursts intensities produced by these impacts with the impact class and the size of the impactors reveals no correlation. This is in conformity with other observations at microwave frequencies and indicates that the process of burst emission is very complex. The impacts K and N produced three microwave bursts which could possibly be due to further fragmentation of these fragments. The results are discussed in the perspective of synchrotron emission from Jupiter and possible enhancements due to an increase in the radial diffusion coefficient. However, this model does not fully explain the observations.     

Rigid body dynamics in the restricted ring problem of N + 1 bodies

The dynamic behavior of a small tri-axial body acted upon by the Newtonian forces of N major bodies of spherical symmetry which forma planar ring configuration is studied in this paper. The equations of the translational-rotational motion of the minor body are derived and its equilibrium states as well as their stability are investigated. This revised version was published online in July 2006 with corrections to the Cover Date.