Measuring stellar oscillations using equivalent widths of absorption lines

Kjeldsen et al. (1995, AJ 109, 1313; astro-ph/9411016) have developed a new technique for measuring stellar oscillations and claimed a detection in the G subgiant eta Boo. The technique involves monitoring temperature fluctuations in a star via their effect on the equivalent width of Balmer lines. In this paper we use synthetic stellar spectra to investigate the temperature dependence of the Balmer lines, Ca II, Fe I, the Mg b feature and the G~band. We present a list of target stars likely to show solar-like oscillations and estimate their expected amplitudes. We also show that centre-to-limb variations in Balmer-line profiles allow one to detect oscillation modes with l<=4, which accounts for the detection by Kjeldsen et al. of modes with degree l=3 in integrated sunlight.Comment: MNRAS (accepted); 7 pages, LaTeX with necessary style file and PostScript figures in a single uuencoded Z-compressed .tar fil

Finding the First Stars: The Hamburg/ESO Objective Prism Survey

We report on a search for extremely metal-poor ([Fe/H]<-3.0) turnoff stars in the Hamburg/ESO objective prism survey (HES). Metal-poor stars are selected by automatic spectral classification. Extensive simulations show that the selection efficiency for turnoff stars of [Fe/H]25% at B<16.5. Since the HES is more than 1 mag deeper than the HK survey of Beers et al. (1992), the HES offers the possibility to efficiently increase the total number of metal-poor stars by at least a factor of 4.Comment: To appear in: Proceedings of ESO/MPA conference "The First Stars". 2 pages, 1 figur

Mechanical effect of van der Waals interactions observed in real time in an ultracold Rydberg gas

We present time-resolved spectroscopic measurements of Rydberg-Rydberg interactions in an ultracold gas, revealing the pair dynamics induced by long-range van der Waals interactions between the atoms. By detuning the excitation laser, a specific pair distribution is prepared. Penning ionization on a microsecond timescale serves as a probe for the pair dynamics under the influence of the attractive long-range forces. Comparison with a Monte Carlo model not only explains all spectroscopic features but also gives quantitative information about the interaction potentials. The results imply that the interaction-induced ionization rate can be influenced by the excitation laser. Surprisingly, interaction-induced ionization is also observed for Rydberg states with purely repulsive interactions

A suboptimality test for two person zero sum Markov games

This paper presents a games version of the nonoptimality test given by Hastings for Markov decision processes. A pure action will be eliminated if compared to some randomized action it performs worse against any of the opponents possible actions

Accounting Facilities in the European Supercomputing Grid DEISA

Account management and resource usage monitoring are essential services for production Grids. The scope of a production Grid infrastructure, the heterogeneity of resources and services, the typical community usage profiles, and the depth of integration of the resource providers regarding operational procedures and policies imply specific requirements for accounting facilities. We present the accounting facilities currently used in production in the Distributed European Infra-structure for the Supercomputing Applications (DEISA). DEISA is a consortium of leading national supercomputing centres currently deploying and operating a persistent, production quality, distributed su-percomputing environment with continental scope. The DEISA accounting facilities gather information from the site-local batch systems and the distributed DEISA user administration system, and generate XML usage records conforming to the OGF usage record specification which are then stored locally in a XML data base at each DEISA site. The distributed accounting information can be fetched by clients such as users, project supervisors, site accounting managers and DEISA supervisors. The information is made available by site-local WSRF-compliant accounting information services that allow for a fine-grained setting of access rights. Each authorized client gets a specific view on the accounting information according to one of the following roles: a) a site accounting manager imports usage records of related home-site users from all DEISA sites for longterm archiving, b) a project supervisor retrieves information to assess the resource usage by his project partners, c) a DEISA supervisor (e.g. someone overlooking the usage on behalf of the DEISA executive committee) gets a report on the global usage of DEISA resources, and d) the user who can retrieve all the accounting information related to his own jobs. The privacy and integrity of the data provided and transferred from the accounting information service running at each site is guaranteed using X.509 certificates for mutual authentication and secure communication channels

Faecal Steroids and n-Alkanes in Lake Sediments

Lake sediments are used as archives for climate and environmental reconstructions. This study investigated if biomarker analyses in lake sediments can be used to reconstruct anthropogenic landscape modifications during Holocene. In contrast to the mineral matrix of sediments and e.g. pollen, plant macro remains and charcoal particles, biomarkers can be more easily translocated within soil profiles before erosion and deposition. Furthermore, a translocation can also occur in lake sediments. Therefore, we tested if biomarker concentrations and patterns correlated with pollen patterns and further paleo environmental proxies in sediments of two maar lakes in the Eifel region. Five core sections of Lake Holzmaar and two core sections of Lake Ulmener Maar were sampled. The analysed core sections contain ca. 10 000 years and a number of data existed from previous analyses (ELSA project). As example for biomarkers for the reconstruction of vegetation changes, n-alkanes were analysed. Steroids incl. bile acids were used as proxies for the deposition of faeces of animals (animal husbandry). Patterns of n-alkanes correlated with pollen data. Parts of the core that show characteristics of dense forest in the catchment area had relatively low amounts of faecal steroids and the steroid patterns indicated the presence of several different animals. In parts of the core that show characteristics for grassland and agricultural fields, faecal steroids showed the presence of animal husbandry. The correlation of biomarker concentrations with pollen data and other data showed that it possible to detect changes in vegetation and land use with biomarker analyses within the catchment area of the two maar lakes

Sistemas integrados de información técnica en fábricas de cemento

Not availableCuando en la actualidad es tratado en el campo industrial el concepto "sistemas de información", se hace generalmente con miras a la cantidad de datos que deben ser preparados para la comercialización. En numerosas empresas es cada vez mayor la tendencia a la rápida información del rendimiento del negocio; en ellas fueron introducidos primeramente los sistemas de información para la Dirección con sus conceptos básicos. En la industria del cemento no está la justificación, para la aplicación de este sistema, en la rapidez de la información sobre el desarrollo del funcionamiento, sino más bien en el volumen de dicha información. Muchas fábricas o sociedades están provistas, además, con instalaciones de elaboración de datos para fines comerciales que, en su capacidad y en el grado de condensación de la información, satisfacen la organización de los datos allí elaborados; pero no comprenden, sin embargo, valores particulares del campo técnico, sino que son primeramente recopilados manualmente y almacenados del mismo modo. Las tareas de esta clase ocupan, sin embargo, una parte considerable del personal disponible, que debe considerar y evaluar las columnas de datos de medida aparecidas en la instalación. La importancia de esta recopilación tampoco es muy elevada, es decir, no son posibles, sin inconvenientes, comprobaciones sobre el comportamiento de la instalación y juicios sobre la exactitud de determinados equipos. Dichas desventajas del tratamiento convencional han originado el deseo, en el caso de los técnicos avanzados, de evaluar los datos disponibles, con la ayuda de instalaciones electrónicas de elaboración de datos, siguiendo diversos criterios

A New Type of Stereoselectivity in Baeyer–Villiger Reactions: Access to E- and Z-Olefins

A new concept for accessing configurationally defined trisubstituted olefins has been developed. Starting from a common ketone precursor of the type 4-ethylidenecyclohexanone, Baeyer–Villiger monooxygenases are employed as catalysts in diastereoselective Baeyer–Villiger reactions leading to the corresponding E- or Z-configurated lactones. Wild-type cyclohexanone monooxygenase (CHMO) as catalyst delivers the E-isomers and a directed evolution mutant the opposite Z-isomers. Subsequent transition metal-catalyzed chemical transformations of a key product containing a vinyl bromide moiety provide a variety of different trisubstituted E- or Z-olefins. A model based on QM/MM sheds light on the origin of this unusual type of diastereoselectivity. In contrast to this biocatalytic approach, traditional Baeyer–Villiger reagents such as m-CPBA fail to show any selectivity, 1:1 mixtures of E- and Z-olefins being formed