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

Use of soil moisture information in yield models

There are no author-identified significant results in this report

Observation of coherent many-body Rabi oscillations

A two-level quantum system coherently driven by a resonant electromagnetic field oscillates sinusoidally between the two levels at frequency $\Omega$ which is proportional to the field amplitude [1]. This phenomenon, known as the Rabi oscillation, has been at the heart of atomic, molecular and optical physics since the seminal work of its namesake and coauthors [2]. Notably, Rabi oscillations in isolated single atoms or dilute gases form the basis for metrological applications such as atomic clocks and precision measurements of physical constants [3]. Both inhomogeneous distribution of coupling strength to the field and interactions between individual atoms reduce the visibility of the oscillation and may even suppress it completely. A remarkable transformation takes place in the limit where only a single excitation can be present in the sample due to either initial conditions or atomic interactions: there arises a collective, many-body Rabi oscillation at a frequency $N^0.5\Omega$ involving all N >> 1 atoms in the sample [4]. This is true even for inhomogeneous atom-field coupling distributions, where single-atom Rabi oscillations may be invisible. When one of the two levels is a strongly interacting Rydberg level, many-body Rabi oscillations emerge as a consequence of the Rydberg excitation blockade. Lukin and coauthors outlined an approach to quantum information processing based on this effect [5]. Here we report initial observations of coherent many-body Rabi oscillations between the ground level and a Rydberg level using several hundred cold rubidium atoms. The strongly pronounced oscillations indicate a nearly complete excitation blockade of the entire mesoscopic ensemble by a single excited atom. The results pave the way towards quantum computation and simulation using ensembles of atoms

Measurement of the electric dipole moments for transitions to rubidium Rydberg states via Autler-Townes splitting

We present the direct measurements of electric-dipole moments for $5P_{3/2}\to nD_{5/2}$ transitions with $20<n<48$ for Rubidium atoms. The measurements were performed in an ultracold sample via observation of the Autler-Townes splitting in a three-level ladder scheme, commonly used for 2-photon excitation of Rydberg states. To the best of our knowledge, this is the first systematic measurement of the electric dipole moments for transitions from low excited states of rubidium to Rydberg states. Due to its simplicity and versatility, this method can be easily extended to other transitions and other atomic species with little constraints. Good agreement of the experimental results with theory proves the reliability of the measurement method.Comment: 12 pages, 6 figures; figure 6 replaced with correct versio

Observation of mesoscopic crystalline structures in a two-dimensional Rydberg gas

The ability to control and tune interactions in ultracold atomic gases has paved the way towards the realization of new phases of matter. Whereas experiments have so far achieved a high degree of control over short-ranged interactions, the realization of long-range interactions would open up a whole new realm of many-body physics and has become a central focus of research. Rydberg atoms are very well-suited to achieve this goal, as the van der Waals forces between them are many orders of magnitude larger than for ground state atoms. Consequently, the mere laser excitation of ultracold gases can cause strongly correlated many-body states to emerge directly when atoms are transferred to Rydberg states. A key example are quantum crystals, composed of coherent superpositions of different spatially ordered configurations of collective excitations. Here we report on the direct measurement of strong correlations in a laser excited two-dimensional atomic Mott insulator using high-resolution, in-situ Rydberg atom imaging. The observations reveal the emergence of spatially ordered excitation patterns in the high-density components of the prepared many-body state. They have random orientation, but well defined geometry, forming mesoscopic crystals of collective excitations delocalised throughout the gas. Our experiment demonstrates the potential of Rydberg gases to realise exotic phases of matter, thereby laying the basis for quantum simulations of long-range interacting quantum magnets.Comment: 10 pages, 7 figure

Consensus Paper: Radiological Biomarkers of Cerebellar Diseases

Hereditary and sporadic cerebellar ataxias represent a vast and still growing group of diseases whose diagnosis and differentiation cannot only rely on clinical evaluation. Brain imaging including magnetic resonance (MR) and nuclear medicine techniques allows for characterization of structural and functional abnormalities underlying symptomatic ataxias. These methods thus constitute a potential source of radiological biomarkers, which could be used to identify these diseases and differentiate subgroups of them, and to assess their severity and their evolution. Such biomarkers mainly comprise qualitative and quantitative data obtained from MR including proton spectroscopy, diffusion imaging, tractography, voxel-based morphometry, functional imaging during task execution or in a resting state, and from SPETC and PET with several radiotracers. In the current article, we aim to illustrate briefly some applications of these neuroimaging tools to evaluation of cerebellar disorders such as inherited cerebellar ataxia, fetal developmental malformations, and immune-mediated cerebellar diseases and of neurodegenerative or early-developing diseases, such as dementia and autism in which cerebellar involvement is an emerging feature. Although these radiological biomarkers appear promising and helpful to better understand ataxia-related anatomical and physiological impairments, to date, very few of them have turned out to be specific for a given ataxia with atrophy of the cerebellar system being the main and the most usual alteration being observed. Consequently, much remains to be done to establish sensitivity, specificity, and reproducibility of available MR and nuclear medicine features as diagnostic, progression and surrogate biomarkers in clinical routine

Aquilegia, Vol. 36 No. 1, Spring 2012: Newsletter of the Colorado Native Plant Society

https://epublications.regis.edu/aquilegia/1110/thumbnail.jp

The search for the ideal biocatalyst

While the use of enzymes as biocatalysts to assist in the industrial manufacture of fine chemicals and pharmaceuticals has enormous potential, application is frequently limited by evolution-led catalyst traits. The advent of designer biocatalysts, produced by informed selection and mutation through recombinant DNA technology, enables production of process-compatible enzymes. However, to fully realize the potential of designer enzymes in industrial applications, it will be necessary to tailor catalyst properties so that they are optimal not only for a given reaction but also in the context of the industrial process in which the enzyme is applied

A construção do mercado para o café em Alto Paraíso de Goiás.

Este estudo apresenta os principais resultados da análise de como habitantes de Alto Paraíso de Goiás estão buscando alternativas para o desenvolvimento sustentável do município, por meio da implantação, pela Embrapa, de projeto relativo ao resgate do café. A mineração e as atividades agropecuárias foram exercidas na região até os anos 60, quando a atividade principal passou a ser o turismo, a partir da criação do Parque Nacional da Chapada dos Veadeiros e da inauguração de Brasília. Em 2000, o fluxo de turistas decaiu devido a problemas relativos à saúde pública, acarretando estagnação da economia local. Nos últimos anos, produtores familiares despertaram para a existência, ali, de um café que pode ser comercializado em nichos de mercado de grãos especiais: orgânicos e de origem definida, e buscaram, na Embrapa, o desenvolvimento de projeto de pesquisa. O estudo na região revelou que por meio do desvelamento de valores - história, cultura e tradições - é possível estabelecer estratégia mais eficiente de busca de mercado, a partir da experiência revelada no trabalho concreto e na cultura dos produtores. E que o desenvolvimento rural deve ser buscado por meio do desenvolvimento de atividades da nova ruralidade e da aplicação de abordagem territorial de desenvolvimento