Marqueurs phénoliques du vieilleissement des vins galiciens de la variété “Mencía” en barrique et par des procédures alternatives.

4 páginas, 2 figuras, 1 tabla.- Trabajo presentado en el Congreso celebrado en Logroño (España) entre el 25 y el 30 de junio de 2006.[EN] The ageing of red wines in oak barrels is a very complex phenomenon involving phenolic compounds (anthocyanins derivatives particularly). The introduction in the market of aged red wines treated with oak wood “chips”, a practice in this moment considered like a fraud in the U.E, it does neccesary to stablish a method that allows to distinguish between traditionally aged wines and those aged by alternative methods. With this aim, the phenolic composition of three monovarietal red wines of Galicia (cv. “Mencía”) fermented in stainless steel tanks with three different treatments, was studied. Wines without ageing (used as “control”), wines aged for 3 months in oak barrels, and wines aged for 3 months in stainless steel tanks with oak “chips” of similar wood and intensity of toasting that barrels. Monthly, along the aging process, all the wines in each treatment (including the “control” wines) were analysed by HPLC-DAD and differences between them studied. In this work, we report the results obtained for the first year of study.[ES] El envejecimiento de vinos tintos en madera es un fenómeno muy complejo en el que los compuestos de naturaleza fenólica (entre ellos los antocianos) juegan un papel relevante. La entrada en el mercado de vinos envejecidos de forma acelerada mediante la aplicación de métodos alternativos al tradicional envejecimiento en barrica, una práctica que en el momento actual es considerada fraudulenta en los paises de la U.E., hace necesario buscar un método analítico que permita distinguir entre unos y otros. Con este objetivo, hemos estudiado la composición fenólica de tres vinos tintos gallegos monovarietales (“Mencía”) fermentados en depósitos de acero inoxidable y sometidos a tres tratamientos diferentes: vinos sin envejecimiento (utilizados como “testigos”), vinos envejecidos durante 3 meses en barrica de roble, y vinos envejecidos durante 3 meses en acero inoxidable con “chips” de roble de similar procedencia y tostado que las barricas. Mensualmente, y a lo largo del proceso de envejecimiento, se han analizado (mediante HPLC-DAD) muestras de los vinos “testigo” y de cada uno de los tratamientos utilizados con el objetivo de establecer diferencias analíticas que permitan reconocer su procedencia. En este trabajo se presentan los resultados obtenidos tras un primer año de estudio.[FR] L’élevage des vins rouges en bois est un phénomène très complexe dans lequel les composants à nature phénolique (parmis ceux-ci les anthocyanes) jouent un rôle remarquable. L'entrée au marché des vins vieillis de manière accélérée, à l'aide de l'application des méthodes alternatives à la méthode traditionnelle en barrique, une pratique qu'au moment actuel est considérée frauduleuse par la U.E., fait nécessaire la recherche d'une méthode analythique qui permette de distinguer entre les uns et les autres. Avec cet objectif, on a étudié la composition phénolique de trois vins rouges galiciens monovariétaux ("Mencía") fermentés dans des cuves d'acier inox, soumis à trois traitements différents: des vins non vieillis (utilisés comme " témoins "), des vins vieillis pendant trois mois en barriques de chêne et des vins vieillis pendant trois mois en cuves d’acier inox avec des "chips" de chêne de provenance et degré de tannage similaire à ceux des barriques. On a analysé tous les mois (par HPLCDAD), et au long du procès d’élevage, des prélèvements des vins "témoins" et de chaque traitement avec l'objectif d'établir des différences analytiques qui permettent de reconnaître leur provenance. Maintenant, on présente les résultats obtenus après la première année d'étude.Peer reviewe

Les dihydroflavonols comme des marqueurs biochimiques de la diversité génétique des variétés blanches de vigne cultivées en Galice (Espagne).

8 páginas, 3 figuras y 3 tablas.- Trabajo presentado en el Congreso celebrado en Logroño (España) entre el 25 y el 30 de junio de 2006.[EN] In order to develop a biochemical method that allows to distinguish between white grape cultivars, the phenolic composition of the main white cultivars from the “Misión Biolóxica de Galicia” germplasm collection were studied. The extracts obtained from peels of the selected cultivars were analysed by high performance liquid chromatography (HPLC with diode array detector) and several phenolic compounds were totally or partly identified. Some of these compounds, especially the called “dihydroflavonols”, have been proved to be of great value as phenolic markers for grape cultivar recognition.[ES] Para tratar de desarrollar un método bioquímico que permita diferenciar entre cultivares blancos de vid, se ha estudiado la composición fenólica de las principales variedades blancas de vid cultivadas en Galicia que se encuentran recogidas en la colección de germoplasma existente en la “Misión Biolóxica de Galicia”. Los extractos fenólicos obtenidos de las pieles de uva de cada una de estas variedades, se han analizado mediante cromatografía líquida (HPLC-DAD), lo que ha permitido identificar (total o parcialmente) diversos compuestos de naturaleza fenólica, entre los que debemos destacar los llamados “dihidroflavonoles”, que se han mostrado como verdaderos marcadores específicos para diferenciar entre las variedades estudiadas.[FR] Pour essayer de développer une méthode biochimique qui permette la différenciation des cépages blancs de vigne, on a étudié la composition phénolique des principales variétés blanches de vigne cultivées en Galice, qui ont été recueillies dans la collection de germoplasme qui existe à la Misión Biolóxica de Galicia. Les extracts phénoliques obtenus des peaux du raisin de chaque variété ont été analysés par chromatographie liquide (HPLCDAD), ce qui a permis d'identifier (de manière totale ou partielle) de divers composants à nature phénolique, parmi lesquels on doit détacher les soi-disants "dihydroflavonols", qui se sont montrés comme de véritables marqueurs spécifiques pour faire une différenciation dans les variétés étudiées.Peer reviewe

Quasinormal ringing of acoustic black holes in Laval nozzles: Numerical simulations

Quasinormal ringing of acoustic black holes in Laval nozzles is discussed. The equation for sounds in a transonic flow is written into a Schr\"{o}dinger-type equation with a potential barrier, and the quasinormal frequencies are calculated semianalytically. From the results of numerical simulations, it is shown that the quasinormal modes are actually excited when the transonic flow is formed or slightly perturbed, as well as in the real black hole case. In an actual experiment, however, the purely-outgoing boundary condition will not be satisfied at late times due to the wave reflection at the end of the apparatus, and a late-time ringing will be expressed as a superposition of "boxed" quasinormal modes. It is shown that the late-time ringing damps more slowly than the ordinary quasinormal ringing, while its central frequency is not greatly different from that of the ordinary one. Using this fact, an efficient way for experimentally detecting the quasinormal ringing of an acoustic black hole is discussed.Comment: 9 pages, 8 figures, accepted for publication in Physical Review

Interplay between Nitrogen Dopants and Native Point Defects in Graphene

To understand the interaction between nitrogen dopants and native point defects in graphene, we have studied the energetic stability of N-doped graphene with vacancies and Stone-Wales (SW) defect by performing the density functional theory calculations. Our results show that N substitution energetically prefers to occur at the carbon atoms near the defects, especially for those sites with larger bond shortening, indicating that the defect-induced strain plays an important role in the stability of N dopants in defective graphene. In the presence of monovacancy, the most stable position for N dopant is the pyridinelike configuration, while for other point defects studied (SW defect and divacancies) N prefers a site in the pentagonal ring. The effect of native point defects on N dopants is quite strong: While the N doping is endothermic in defect-free graphene, it becomes exothermic for defective graphene. Our results imply that the native point defect and N dopant attract each other, i.e., cooperative effect, which means that substitutional N dopants would increase the probability of point defect generation and vice versa. Our findings are supported by recent experimental studies on the N doping of graphene. Furthermore we point out possibilities of aggregation of multiple N dopants near native point defects. Finally we make brief comments on the effect of Fe adsorption on the stability of N dopant aggregation.Comment: 10 pages, 5 figures. Figure 4(g) and Figure 5 are corrected. One additional table is added. This is the final version for publicatio

Hooge's Constant of Carbon Nanotube Field Effect Transistors

The 1/f noise in individual semiconducting carbon nanotubes (s-CNT) in a field effect transistor configuration has been measured in ultra-high vacuum and following exposure to air. The amplitude of the normalized current spectral noise density is independent of source-drain current, indicating the noise is due to mobility rather than number fluctuations. Hooge's constant for s-CNT is found to be 9.3 plus minus 0.4x10^-3. The magnitude of the 1/f noise is substantially degreased by exposing the devices to air

High Ratio of 44Ti/56Ni in Cas A and Axisymmetric Collapse-Driven Supernova Explosion

The large abundance ratio of $^{44}Ti/^{56}Ni$ in Cas A is puzzling. In fact, the ratio seems to be larger than the theoretical constraint derived by Woosley & Hoffman (1991). However, this constraint is obtained on the assumption that the explosion is spherically symmetric, whereas Cas A is famous for the asymmetric form of the remnant. Recently, Nagataki et al. (1997) calculated the explosive nucleosynthesis of axisymmetrically deformed collapse-driven supernova. They reported that the ratio of $^{44}Ti/^{56}Ni$ was enhanced by the stronger alpha-rich freezeout in the polar region. In this paper, we apply these results to Cas A and examine whether this effect can explain the large amount of $^{44}Ti$ and the large ratio of $^{44}Ti/^{56}Ni$. We demonstrate that the conventional spherically symmetric explosion model can not explain the $^{44}$Ti mass produced in Cas A if its lifetime is shorter than $\sim$ 80 years and the intervening space is transparent to the gamma-ray line from the decay of $^{44}$Ti. On the other hand, we show the axisymmetric explosion models can solve the problem. We expect the same effect from a three dimensionally asymmetric explosion, since the stronger alpha-rich freezeout will also occur in that case in the region where the larger energy is deposited.Comment: 10 pages, LaTeX text and 3 postscript figure

Explosive Nucleosynthesis in Axisymmetrically Deformed Type II Supernovae

Explosive nucleosynthesis under the axisymmetric explosion in Type II supernova has been performed by means of two dimensional hydrodynamical calculations. We have compared the results with the observations of SN 1987A. Our chief findings are as follows: (1) $^{44}Ti$ is synthesized so much as to explain the tail of the bolometric light curve of SN 1987A. We think this is because the alpha-rich freezeout takes place more actively under the axisymmetric explosion. (2) $^{57}Ni$ and $^{58}Ni$ tend to be overproduced compared with the observations. However, this tendency relies strongly on the progenitor's model. We have also compared the abundance of each element in the mass number range $A= 16-73$ with the solar values. We have found three outstanding features. (1) For the nuclei in the range $A=16-40$, their abundances are insensitive to the initial form of the shock wave. This insensitivity is favored since the spherical calculations thus far can explain the solar system abundances in this mass range. (2) There is an enhancement around A=45 in the axisymmetric explosion compared with the spherical explosion fairly well. In particular, $^{44}Ca$, which is underproduced in the present spherical calculations, is enhanced significantly. (3) In addition, there is an enhancement around A=65. This tendency does not rely on the form of the mass cut but of the initial shock wave. This enhancement may be the problem of the overproduction in this mass range, although this effect would be relatively small since Type I supernovae are chiefly responsible for this mass number range.Comment: 32 pages, 12 figures, LaTe

Nucleosynthesis in ONeMg Novae: Models versus Observations to Constrain the Masses of ONeMg White Dwarfs and Their Envelopes

Nucleosynthesis in ONeMg novae has been investigated with the wide ranges of three parameters, i.e., the white dwarf mass, the envelope mass at ignition, and the initial composition. A quasi-analytic one-zone approach is used with an up-to-date nuclear reaction network. The nucleosynthesis results show correlation with the peak temperatures or the cooling timescales during outbursts. Among the combinations of white dwarf and envelope masses which give the same peak temperature, the explosion is more violent for a lower white dwarf mass owing to its smaller gravitational potential. Comparison of the nucleosynthesis results with observations implies that at least two-third of the white dwarf masses for the observed ONeMg novae are $\simeq 1.1 M_\odot$, which are significantly lower than estimated by previous hydrodynamic studies but consistent with the observations of V1974 Cyg. Moreover, the envelope masses derived from the comparison are $\gtrsim 10^{-4} M_\odot$, which are in good agreement with the ejecta masses estimated from observations but significantly higher than in previous hydrodynamic studies. With such a low mass white dwarf and a high mass envelope, the nova can produce interesting amounts of $\gamma$-ray emitters $^7$Be, $^{22}$Na, and $^{26}$Al. We suggest that V1974 Cyg has produced $^{22}$Na as high as the upper limit derived from the COMPTEL survey. In addition, a non-negligible part of the Galactic $^{26}$Al may originate from ONeMg novae, if not the major contributors. Both the future INTEGRAL survey for these $\gamma$-ray emitters and abundance estimates derived from ultraviolet, optical, and near infrared spectroscopies will impose a severe constraint on the current nova models.Comment: 21 pages, 23 figures, to appear in the Astrophysical Journal, Vol. 523, No.1, September 20, 1999; preprint with embedded images can be obtained from http://th.nao.ac.jp/~wanajo/journal/onenova.p

Ultra-stable performance of an underground-based laser interferometer observatory for gravitational waves

In order to detect the rare astrophysical events that generate gravitational wave (GW) radiation, sufficient stability is required for GW antennas to allow long-term observation. In practice, seismic excitation is one of the most common disturbances effecting stable operation of suspended-mirror laser interferometers. A straightforward means to allow more stable operation is therefore to locate the antenna, the ``observatory'', at a ``quiet'' site. A laser interferometer gravitational wave antenna with a baseline length of 20m (LISM) was developed at a site 1000m underground, near Kamioka, Japan. This project was a unique demonstration of a prototype laser interferometer for gravitational wave observation located underground. The extremely stable environment is the prime motivation for going underground. In this paper, the demonstrated ultra-stable operation of the interferometer and a well-maintained antenna sensitivity are reported.Comment: 8 pages, to appear on PR

Optimal Location of Two Laser-interferometric Detectors for Gravitational Wave Backgrounds at 100 MHz

Recently, observational searches for gravitational wave background (GWB) have been developed and given constraints on the energy density of GWB in a broad range of frequencies. These constraints have already resulted in the rejection of some theoretical models of relatively large GWB spectra. However, at 100 MHz, there is no strict upper limit from direct observation, though an indirect limit exists due to He4 abundance due to big-bang nucleosynthesis. In our previous paper, we investigated the detector designs that can effectively respond to GW at high frequencies, where the wavelength of GW is comparable to the size of a detector, and found that the configuration, a so-called synchronous-recycling interferometer is best at these sensitivity. In this paper, we investigated the optimal location of two synchronous-recycling interferometers and derived their cross-correlation sensitivity to GWB. We found that the sensitivity is nearly optimized and hardly changed if two coaligned detectors are located within a range 0.2 m, and that the sensitivity achievable in an experiment is far below compared with the constraint previously obtained in experiments.Comment: 17 pages, 6 figure