A new assemblage of ray-finned fishes (Teleostei) from the Lower Oligocene “Schistes à Meletta” from the Glières plateau, Bornes Massif, eastern France

A recently discovered fish assemblage from the “Schistes à Meletta” facies (Lower Oligocene) of the Glières Plateau, Bornes Massif, Haute–Savoie, eastern France is described. The assemblage, comprising specimens ranging from fully-articulated skeletons to isolated scattered ossifications, is composed of Anenchelum cf. glarisianum, Pristigenys sp., Fistularia sp., Caranx cf. glarisianus alongside indeterminate teleosts. This new assemblage greatly increases the fish diversity previously known from the “Schistes à Meletta” of this area. The fauna shows biogeographic affinities with assemblages from the Peritethys domain, in particular from the Helvetic molassic basin and from the Paratethys. The genera identified at the Glières locality are represented today by species living in tropical nearshore environments together with species from the open sea. A possible explanation is that the environment of deposition was rather deep, and that shallow-water fishes were brought in by turbidity currents

How to Measure Scope Variables when no Metrics Exist : Application to Landscape Quality Measurement and Hedonic Price Evaluation

Landscape is an example of a non-market good where no metrics exist to measure its quality. The paper proposes an original methodology to nevertheless estimate scope variables in those circumstances, allowing then to better test if people's willingnesstopay for such good is sensitive to the scope. The methodology is based on techniques developed in the context of multicriteria decision analysis. It is applied to assess the quality of the landscape of several Swiss alpine resorts. This assessment is then used as an explanatory variable in a hedonic price function to explain the rent of apartments and to derive an implicit price of the landscape quality

Spurious signals in DQF spectroscopy: two-shot stimulated echoes

The most widely used technique for double-quantum filtered (DQF) single-voxel spectroscopy (SVS) is based on a symmetric PRESS sequence with two additional spatially unselective π/2 pulses, one of which is usually frequency selective. The actual filtering, rejecting signals from all uncoupled resonances, can be done by suitable phase cycling of the rf pulses in successive shots, but in practice gradient filtering is always used. Under usual conditions the sequence repetition time is comparable to the spin-lattice relaxation time, and a stimulated echo is formed by five out of the ten rf pulses in two consecutive shots. This echo is not filtered out by the gradients, and additional phase cycling is needed to eliminate it. Its spatial origin is the full transverse slice selected by the last pulse of the PRESS sequence. The SVS shimming procedure may create an important field variation in this slice (outside the volume of interest VOI). Water singlet signals therefore appear in a band of frequencies other than 4.7 ppm, and remain unaffected by water suppression pulses. In practice phase-alternation schemes can reduce these spurious signals by several orders of magnitude, but even then they may mask the weak metabolite signals of interest. We describe a strategy to minimize these spurious signals and propose a 16-step phase cycling scheme that attenuates the stimulated echo in every two-step subcycl

Barremian and Aptian (Cretaceous) sharks and rays from Speeton, Yorkshire, north-east England

Bulk sampling of a number of horizons within the upper part of the Speeton Clay Type section has produced teeth and other remains of sharks and rays from several poorly studied horizons. At least 10 shark and two ray species were recorded, with two sharks, Pteroscyllium speetonensis and Palaeobrachaelurus mitchelli, being described as new. The oldest occurrences of the family Anacoracadae and the genus Pteroscyllium, as well as the youngest occurrence of the genus Palaeobrachaelurus, were recorded. The palaeoenvironmental significance of the faunas is briefly discussed

La stratigraphie isotopique du Strontium est-elle une méthode fiable pour dater les plates-formes carbonatées à la transition du Barrémien à l'Aptien ? Révision de cas d'études en Téthys occidentale.

Strontium-isotope measurements on Lower Cretaceous marine rocks derive from belemnite material sampled in ammonite-constrained basinal successions. A group of values with a narrow range across the Barremian/Aptian boundary does not allow the separation of the uppermost Barremian (Martelites sarasini ammonite zone) from the lower Aptian pro parte (Deshayesites oglanlensis-D. forbesi ammonite zones). Growing numbers of studies applied Sr-Isotope Stratigraphy (SIS) on Barremian-Aptian shallow-marine sequences (Urgonian facies) in order to solve controversial results obtained by using different shallow-water biological time markers. Based on re-examination of case studies, we conclude that Sr-isotope values can neither be used to prove nor to disprove the location of the putative Barremian/Aptian boundary based on biostratigraphy. Pending more data available, SIS should be used with caution for dating ammonite-free carbonate sediments in the corresponding time interval.Les mesures de l'isotope du Strontium dans des roches carbonatées marines du Crétacé inférieur proviennent de restes de bélemnites récoltés dans des séries de bassins datées directement par ammonites. Autour de la limite Barrémien/Aptien, une gamme étroite de valeurs du Strontium ne permet pas de distinguer le Barrémien supérieur (Zone d'ammonite à Martelites sarasini) de l'Aptien inférieur pro parte (zones d'ammonite à Deshayesites oglanlensis et D. forbesi). Pourtant, l’application de la Stratigraphie Isotopique du Strontium (SIS) sur des séquences marines carbonatées barrémo–aptiennes (à faciès urgonien) apparaît dans un nombre croissant d’études, essentiellement afin de résoudre les datations souvent controversées des marqueurs biologiques d’environnements peu profonds. La révision de ces cas d'étude montre que l’utilisation des valeurs de l'isotope du Strontium n’est pas un outil fiable pour prouver ou réfuter la localisation de la limite Barrémien/Aptien telle que déduite par la biostratigraphie. Dans l'attente de données complémentaires, la SIS doit être utilisée avec précaution pour dater des séries carbonatées non datées directement par ammonites dans l'intervalle de temps concerné

Scaling of the distribution of fluctuations of financial market indices

We study the distribution of fluctuations over a time scale $\Delta t$ (i.e., the returns) of the S&P 500 index by analyzing three distinct databases. Database (i) contains approximately 1 million records sampled at 1 min intervals for the 13-year period 1984-1996, database (ii) contains 8686 daily records for the 35-year period 1962-1996, and database (iii) contains 852 monthly records for the 71-year period 1926-1996. We compute the probability distributions of returns over a time scale $\Delta t$, where $\Delta t$ varies approximately over a factor of 10^4 - from 1 min up to more than 1 month. We find that the distributions for $\Delta t \leq$ 4 days (1560 mins) are consistent with a power-law asymptotic behavior, characterized by an exponent $\alpha \approx 3$, well outside the stable L\'evy regime $0 < \alpha < 2$. To test the robustness of the S&P result, we perform a parallel analysis on two other financial market indices. Database (iv) contains 3560 daily records of the NIKKEI index for the 14-year period 1984-97, and database (v) contains 4649 daily records of the Hang-Seng index for the 18-year period 1980-97. We find estimates of $\alpha$ consistent with those describing the distribution of S&P 500 daily-returns. One possible reason for the scaling of these distributions is the long persistence of the autocorrelation function of the volatility. For time scales longer than $(\Delta t)_{\times} \approx 4$ days, our results are consistent with slow convergence to Gaussian behavior.Comment: 12 pages in multicol LaTeX format with 27 postscript figures (Submitted to PRE May 20, 1999). See http://polymer.bu.edu/~amaral/Professional.html for more of our work on this are

Biocatalyzed C-C bond formation for the production of alkaloids

Traditional methods of chemical synthesis of alkaloids exhibit various problems such as lack of enantioselectivity, the use of toxic chemical and intermediates, and multiple numbers of synthetic steps. Consequently, various enzymatic methods for the formation of C-C bonds in the alkaloid skeleton have been developed. Herein, we report advances achieved in the enzymatic or chemo-enzymatic synthesis of pharmaceutically important alkaloids that employ three C-C bond forming enzymes: two Pictet-Spenglerases and the oxidative C-C bond forming flavoenzyme Berberine Bridge Enzyme. Protein engineering studies, improving the substrate scope of these enzymes, and thereby leading to the synthesis of non-natural alkaloids possessing higher or newer pharmacological activities, are also discussed. Furthermore, the integration of these biocatalysts with other enzymes, in multi-enzymatic cascades for the enantioselective synthesis of alkaloids, is also reviewed. Current results suggest that these enzymes hold great promise for the generation of C-C bonds in the selective synthesis of alkaloid compounds possessing diverse pharmacological properties