Among the largest objects in the main belt, asteroid 4 Vesta is unique in showing a basaltic crust. It is also the biggest member of the Vesta family, which is supposed to originate from a large ...cratering event about 1 Gyr ago (Marzari et al. 1996, A&A, 316, 248). Most of the members of the Vesta family for which a spectral classification is available show a V-type spectra. Due to their characteristic infrared spectrum, V-type asteroids are easily distinguished. Before the discovery of 1459 Magnya (Lazzaro et al. 2000, Science, 288, 2033) and of several V-type NEA (Xu et al. 1995, Icarus, 115, 1), all the known V-type asteroids were members of the Vesta family. Recently two V-type asteroids, 809 Lundia and 956 Elisa, (Florczak et al. 2002, Icarus, 159, 178) have been discovered well outside the limits of the family, near the Flora family. We currently know 22 V-type asteroids outside the family, in the inner asteroid belt. In this work we investigate the possibility that these objects are former family members that migrated to their current positions via the interplay of Yarkovsky effect and nonlinear secular resonances. The main dynamical feature of 956 Elisa and 809 Lundia is that they are currently inside the 2(g - g6) + s - s6 (z2 by Milani & Knezevic 1994, Icarus, 107, 219) secular resonance. Our investigations show that members of the Vesta dynamical family may drift in three-body and weak secular resonances until they are captured in the strong z2 secular resonance. Only asteroids with diameters larger than 16 km can remain in one of the three-body or secular resonances long enough to reach the region of the z2 resonance. This two-step mechanism of capture into the z2 resonance could explain: i) the current resonant orbits of 956 Elisa and 809 Lundia; ii) why their size is significantly larger than that of the typical member of the Vesta family; and iii) provide a lower limit on the Vesta family age. We believe that other V-type asteroids could have followed the same path, and could currently be inside the z2 resonance. In an forthcoming article of this series we will investigate the role that other mechanisms of dynamical mobility, such as close encounters with massive asteroids, may have played in causing the current orbital distribution of the remaining 20 other V-type asteroids.
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FMFMET, NUK, UL, UM, UPUK
LM124 operational amplifiers from three different manufacturers are irradiated with 60 Co gamma rays and neutrons. During neutrons irradiation, one of the three integrated circuits exhibits an ...unexpected slew rates increase while its open loop gain and supply bias current follow the usual monotonic decrease as described in the literature. Analysis at circuit level shows that this phenomenon is due to an increase in the radiation-induced base current of the transistor used as buffer stage in the amplification chain. It is then demonstrated that a slight modification of the buffer transistor design, which is not implemented on the two other devices, enhances this phenomenon. Finally, the impact of the buffer transistor design on displacement damage and total ionizing dose response is investigated.
Binary stars in open clusters are very useful targets in constraining the nucleosynthesis process. The luminosities of the stars are known because the distances of the clusters are also known, so ...chemical peculiarities can be linked directly to the evolutionary status of a star. We carried out a detailed spectroscopic analysis to derive the atmospheric parameters for 16 red giants in binary systems and the chemical composition of 11 of them in the open clusters NGC 2360, NGC 3680, and NGC 5822. We obtained abundances of C, N, O, Na, Mg, Al, Ca, Si, Ti, Ni, Cr, Y, Zr, La, Ce, and Nd. The atmospheric parameters of the studied stars and their chemical abundances were determined using high-resolution optical spectroscopy. We employ the local thermodynamic equilibrium model atmospheres of Kurucz and the spectral analysis code moog. The abundances of the light elements were derived using the spectral synthesis technique. Finally, rotational velocities were also determined and their values were compared with those already determined for field giant stars.
•Study of the oxidation steps of 4,6-DMDBT by different techniques using a BDD anode.•4,6-DMDBT was removed after 60 min of electrolysis at Ean = 1.50 V.•Selective oxidation of 4,6-DMDBT to sulfoxide ...or sulfone.•The conversion depended on concentration, applied potential, and water content.•A small amount of dimers was formed during the electrochemical oxidation.
The electrochemical oxidation of 4,6-dimethyldibenzothiophene (4,6-DMDBT) at low concentrations on a BDD anode was investigated in a monophasic acetonitrile (93.5% v/v)–water (6.5% v/v, 0.01 M LiClO4) solution. Two oxidation steps related to the sequential formation of sulfoxide and sulfone derivatives were identified. Kinetic parameters such as the electron transfer coefficient α, the number of electrons nα involved in the rate-determining step, the total number of electrons n, the reaction rate constant k0 and the diffusion coefficient D of 4,6-DMDBT for the first transformation were determined by cyclic voltammetry, differential pulse voltammetry (DPV), square wave voltammetry and bulk electrolysis under potentiostatic conditions. The process was bielectronic with α = 0.57, nα = 1, k0 = 7.46 × 10−6 cm s−1 and D = 2.30 × 10−6 cm2 s−1. DPV was the most sensitive electroanalytical technique. Using 27 mg L−1 of 4,6-DMTDB, DPV allowed determining a conversion of 91% to sulfoxide after 60 min of electrolysis in a BDD/BDD cell at an anodic potential of 1.50 V, with an apparent rate constant of 0.034 min−1. The electrochemical characterization was corroborated via gas chromatography–mass spectrometry and ultra-high performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry, confirming the formation of the sulfoxide in the first step and the sulfone in the second one as main products, alongside a minor proportion of dimers.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The electrochemical oxidation of dibenzothiophene and two derivatives, namely 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene, was investigated either separately or as a mixture, on a BDD ...anode in a miscible acetonitrile (87.5% v/v)–water (12.5% v/v, 0.01M NaNO3) solution. Linear sweep voltammetry, cyclic voltammetry, chronoamperometry and bulk electrolysis under potentiostatic conditions suggested the probable occurrence of two pathways: direct electrochemical oxidation and indirect reaction with hydroxyl radicals and other reactive oxygen species formed at the BDD anode surface during water discharge. The products extracted upon electrolysis at 1.5 and 2.0V vs. SCE were analyzed by Fourier-transform infrared spectroscopy, gas chromatography–mass spectrometry and ultra-high performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry (UHPLC-ESI-Q-TOF-MS). The main molecules identified were the corresponding sulfoxides or sulfones, depending on the applied anodic potential. Possible oxidation routes for the dibenzothiophene compounds are proposed.
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•Electrochemical oxidation of dibenzothiophenes in CH3CN/H2O using a BDD anode•Oxidation is direct or mediated by reactive oxygen species like OH.•Selective oxidation of single compounds or mixtures to sulfoxides or sulfones•The conversion depends on concentration, applied potential and water content.•The electrochemical reactivity on BDD decreases as: 4,6-DMDBT≥4-MDBT>DBT.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Long-term trends of temperature variations across the southern Andes (37-55 degrees S) are examined using a combination of instrumental and tree-ring records. A critical appraisal of surface air ...temperature from station records is presented for southern South America during the 20th century. For the interval 1930-1990, three major patterns in temperature trends are identified. Stations along the Pacific coast between 37 and 43 degrees S are characterized by negative trends in mean annual temperature with a marked cooling period from 1950 to the mid-1970s. A clear warming trend is observed in the southern stations (south of 46 degrees S), which intensifies at higher latitudes. No temperature trends are detected for the stations on the Atlantic coast north of 45 degrees S. In contrast to higher latitudes in the Northern Hemisphere where annual changes in temperature are dominated by winter trends, both positive and negative trends in southern South America are due to mostly changes in summer (December to February) temperatures. Changes in the Pacific Decadal Oscillation (PDO) around 1976 are felt in summer temperatures at most stations in the Pacific domain, starting a period with increased temperature across the southern Andes and at higher latitudes. Tree-ring records from upper-treeline were used to reconstruct past temperature fluctuations for the two dominant patterns over the southern Andes. These reconstructions extend back to 1640 and are based on composite tree-ring chronologies that were processed to retain as much low-frequency variance as possible. The resulting reconstructions for the northern and southern sectors of the southern Andes explain 55% and 45% of the temperature variance over the interval 1930-1989, respectively. Cross-spectral analysis of actual and reconstructed temperatures over the common interval 1930-1989, indicates that most of the explained variance is at periods >10 years in length. At periods >15 years, the squared coherency between actual and reconstructed temperatures ranges between 0.6 and 0.95 for both reconstructions. Consequently, these reconstructions are especially useful for studying multi-decennial temperature variations in the South American sector of the Southern Hemisphere over the past 360 years. As a result, it is possible to show that the temperatures during the 20th century have been anomalously warm across the southern Andes. The mean annual temperatures for the northern and southern sectors during the interval 1900-1990 are 0.53 degrees C and 0.86 degrees C above the 1640-1899 means, respectively. These findings placed the current warming in a longer historical perspective, and add new support for the existence of unprecedented 20th century warming over much of the globe. The rate of temperature increase from 1850 to 1920 was the highest over the past 360 years, a common feature observed in several proxy records from higher latitudes in the Northern Hemisphere. Local temperature regimes are affected by changes in planetary circulation, with in turn are linked to global sea surface temperature (SST) anomalies. Therefore, we explored how temperature variations in the southern Andes since 1856 are related to large-scale SSTs on the South Pacific and South Atlantic Oceans. Spatial correlation patterns between the reconstructions and SSTs show that temperature variations in the northern sector of the southern Andes are strongly connected with SST anomalies in the tropical and subtropical Pacific. This spatial correlation pattern resembles the spatial signature of the PDO mode of SST variability over the South Pacific and is connected with the Pacific-South American (PSA) atmospheric pattern in the Southern Hemisphere. In contrast, temperature variations in the southern sector of the southern Andes are significantly correlated with SST anomalies over most of the South Atlantic, and in less degree, over the subtropical Pacific. This spatial correlation field regressed against SST resembles the "Global Warming" mode of SST variability, which in turn, is linked to the leading mode of circulation in the Southern Hemisphere. Certainly, part of the temperature signal present in the reconstructions can be expressed as a linear combination of four orthogonal modes of SST variability. Rotated empirical orthogonal function analysis, performed on SST across the South Pacific and South Atlantic Oceans, indicate that four discrete modes of SST variability explain a third, approximately, of total variance in temperature fluctuations across the southern Andes. PUBLICATION ABSTRACT
Total dose effect remains one challenging issue for electronics systems intended to space applications. For high total dose missions, like Jupiter missions, or for scientific instruments for which ...functionality and precision must be guaranteed, dose effect is one of the main drawbacks. So, new solutions must be found in order to ensure the reliability of the mission. In this paper, an analysis of a thermal annealing approach is done. This approach consists of applying isothermal annealing cycles to a device such that its electrical characteristics can be regenerated after being degraded by total ionizing dose. The analysis is based on experimental results obtained on Power MOSFET and CMOS APS imager. The impact of electric field during annealing is also investigated. It is shown that thermal annealing can be applied to electronic devices in order to extend their lifetime.
The North Atlantic Oscillation (NAO) is the most important source of winter atmospheric variability in the northern hemisphere. NAO inversely reflects the precipitation regime, which plays a ...fundamental role in Mediterranean regions, e.g., by recharging the water table. As no attempt has been made thus far to analyze the relationship between NAO variability and tree radial growth in coastal Mediterranean conifers, this paper identifies the monthly, winter, annual, and decadal influence of NAO on tree-ring chronologies of six planted Pinus pinea L. populations distributed along the Tyrrhenian coasts of central Italy. Through multidimensional analyses, we identified tree-ring chronology associations in two main groups. The influence of NAO on the regional chronologies was identified with correlation functions for the comparison period between 1949 and 2003 at both annual and decadal timescales. Results indicate that winter NAO influence on radial tree growth at annual and decadal timescales may depend on geographical location, site characteristics, and the age structure of tree-ring chronologies. These results contribute to a better understanding of the P. pinea coastal forest ecology and provide evidence of large-scale climatic forcings that influence forest Mediterranean ecosystems.
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BFBNIB, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We report on the analysis of high-resolution optical spectra of four symbiotic stars CD-43°14304, Hen 3-863, Hen 3-1213, and StH alpha 176. The chemical composition of the atmospheres of the ...investigated stars shows that they are all metal-poor K giants with metallicities around Fe/H -1.0. All stars show an enrichment of the elements created by slow neutron-capture reactions. The luminosities obtained for the symbiotic star CD-43°14304 and probably for Hen 3-1213 are below those of the asymptotic giant branch (AGB) stars that started helium-burning (via thermal pulses) and became self-enriched in the neutron-capture elements. Therefore, their abundance peculiarities are due to mass transfer from the previous thermally pulsing AGB star (now the white dwarf), overabundant in s-process elements. For the stars Hen 3-863 and StH alpha 176, the uncertainties due to the distance (and interstellar absorption as well) prevent a reliable determination of the luminosity. The heavy-element abundance distribution of these four analyzed symbiotics is similar to that of the three symbiotics previously analyzed (AG Dra, BD-21°3873, and Hen 2-467). Finally, their general abundance pattern follows the halo standard abundance.
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