Observation of Interactions between Trapped Ions and Ultracold Rydberg Atoms

We report on the observation of interactions between ultracold Rydberg atoms and ions in a Paul trap. The rate of observed inelastic collisions, which manifest themselves as charge transfer between the Rydberg atoms and ions, exceeds that of Langevin collisions for ground state atoms by about three orders of magnitude. This indicates a huge increase in interaction strength. We study the effect of the vacant Paul trap's electric fields on the Rydberg excitation spectra. To quantitatively describe the exhibited shape of the ion loss spectra, we need to include the ion-induced Stark shift on the Rydberg atoms. Furthermore, we demonstrate Rydberg excitation on a dipole-forbidden transition with the aid of the electric field of a single trapped ion. Our results confirm that interactions between ultracold atoms and trapped ions can be controlled by laser coupling to Rydberg states. Adding dynamic Rydberg dressing may allow for the creation of spin-spin interactions between atoms and ions, and the elimination of collisional heating due to ionic micromotion in atom-ion mixtures.Comment: 7 pages, 5 figures, including appendices. Note that the title has been changed in version

Observation of collisions between cold Li atoms and Yb+^+ ions

We report on the observation of cold collisions between $^6$Li atoms and Yb$^+$ ions. This combination of species has recently been proposed as the most suitable for reaching the quantum limit in hybrid atom-ion systems, due to its large mass ratio. For atoms and ions prepared in the $^2S_{1/2}$ ground state, the charge transfer and association rate is found to be at least~10$^{3}$ times smaller than the Langevin collision rate. These results confirm the excellent prospects of $^6$Li--Yb$^+$ for sympathetic cooling and quantum information applications. For ions prepared in the excited electronic states $^2P_{1/2}$, $^2D_{3/2}$ and $^2F_{7/2}$, we find that the reaction rate is dominated by charge transfer and does not depend on the ionic isotope nor the collision energy in the range $\sim$~1--120~mK. The low charge transfer rate for ground state collisions is corroborated by theory, but the $4f$ shell in the Yb$^+$ ion prevents an accurate prediction for the charge transfer rate of the $^2P_{1/2}$, $^2D_{3/2}$ and $^2F_{7/2}$ states. Using \textit{ab initio} methods of quantum chemistry we calculate the atom-ion interaction potentials up to energies of 30$\times 10^3$~cm$^{-1}$, and use these to give qualitative explanations of the observed rates.Comment: 8 pages, 7 figures (including appendices

Trapped ions in Rydberg-dressed atomic gases

We theoretically study trapped ions that are immersed in an ultracold gas of Rydberg-dressed atoms. By off-resonant coupling on a dipole-forbidden transition, the adiabatic atom-ion potential can be made repulsive. We study the energy exchange between the atoms and a single trapped ion and find that Langevin collisions are inhibited in the ultracold regime for these repulsive interactions. Therefore, the proposed system avoids recently observed ion heating in hybrid atom-ion systems caused by coupling to the ion's radio frequency trapping field and retains ultracold temperatures even in the presence of excess micromotion.Comment: 9 pages, 5 figures including appendice

The grey partridge in the UK: population status, research, policy and prospects

La perdiz pardilla en el Reino Unido: estado de la población, investigación, gestión y perspectivas Durante los últimos cincuenta años, los efectivos de la perdiz pardilla (Perdix perdix) han descendido catastróficamente en el Reino Unido. Por el contrario, el Programa de Recuento de la Perdiz de la GWCT (Fundación para la Conservación de la Caza y la Fauna Salvaje) presenta un 81% de aumento desde el año 2000 en los lugares del Reino Unido en que interviene. En este estudio exploramos los antecedentes y las razones de estos resultados tan contradictorios. Las investigaciones de la GWCT han tenido como consecuencias recomendaciones científicamente demostradas para la mejora del medio ambiente de la perdiz en el Reino Unido, desde los requerimientos del hábitat hasta la densidad de depredadores. Dichas investigaciones han influido en la política gubernamental del Reino Unido, que ahora incluye uno de los proyectos de Europa más orientadas hacia la conservación y más flexible en cuanto a hábitat y agricultura, lo que permite a los gestores del territorio recuperar gran parte del hábitat costero de la perdiz pardilla. Actualmente, los proyectos sobre agricultura y medio ambiente no abarcan la selección de los depredadores más comunes, de manera que son principalmente los cotos de caza con guardabosques privados los que han aplicado todas las medidas de gestión. El futuro de la perdiz pardilla en el Reino Unido reside en el equilibrio entre la economía de la producción agrícola, las medidas agro–medioambientales, y la caza.La perdiz pardilla en el Reino Unido: estado de la población, investigación, gestión y perspectivas Durante los últimos cincuenta años, los efectivos de la perdiz pardilla (Perdix perdix) han descendido catastróficamente en el Reino Unido. Por el contrario, el Programa de Recuento de la Perdiz de la GWCT (Fundación para la Conservación de la Caza y la Fauna Salvaje) presenta un 81% de aumento desde el año 2000 en los lugares del Reino Unido en que interviene. En este estudio exploramos los antecedentes y las razones de estos resultados tan contradictorios. Las investigaciones de la GWCT han tenido como consecuencias recomendaciones científicamente demostradas para la mejora del medio ambiente de la perdiz en el Reino Unido, desde los requerimientos del hábitat hasta la densidad de depredadores. Dichas investigaciones han influido en la política gubernamental del Reino Unido, que ahora incluye uno de los proyectos de Europa más orientadas hacia la conservación y más flexible en cuanto a hábitat y agricultura, lo que permite a los gestores del territorio recuperar gran parte del hábitat costero de la perdiz pardilla. Actualmente, los proyectos sobre agricultura y medio ambiente no abarcan la selección de los depredadores más comunes, de manera que son principalmente los cotos de caza con guardabosques privados los que han aplicado todas las medidas de gestión. El futuro de la perdiz pardilla en el Reino Unido reside en el equilibrio entre la economía de la producción agrícola, las medidas agro–medioambientales, y la caza.Numbers of grey partridges (Perdix perdix) have declined catastrophically over the last 50 years in the UK. By contrast, the Partridge Count Scheme of the Game & Wildlife Conservation Trust (GWCT) shows an 81% increase on participating UK sites since 2000. We explore the background and reasons for this conflicting picture. GWCT research has led to scientifically proven recommendations for improving the UK partridge environment, ranging from habitat requirements to predator density. The research has influenced UK government policy, which now includes one of the most conservation–oriented and flexible agri–environment schemes in Europe, allowing land managers to recover much of the cost of grey partridge habitat creation. Culling common predators is not covered by agri–environment schemes, so it is primarily shooting estates with private gamekeepers that have implemented the full package of management measures. The future fate of the grey partridge in the UK rests on the balance between the economics of agricultural production, agri–environment measures and shooting

Dynamical Diffraction Theory for Wave Packet Propagation in Deformed Crystals

We develop a theory for the trajectory of an x ray in the presence of a crystal deformation. A set of equations of motion for an x-ray wave packet including the dynamical diffraction is derived, taking into account the Berry phase as a correction to geometrical optics. The trajectory of the wave packet has a shift of the center position due to a crystal deformation. Remarkably, in the vicinity of the Bragg condition, the shift is enhanced by a factor $\omega /\Delta \omega$ ($\omega$: frequency of an x ray, $\Delta\omega$: gap frequency induced by the Bragg reflection). Comparison with the conventional dynamical diffraction theory is also made.Comment: 4 pages, 2 figures. Title change

From bcc to fcc: interplay between oscillating long-range and repulsive short-range forces

This paper supplements and partly extends an earlier publication, Phys. Rev. Lett. 95, 265501 (2005). In $d$-dimensional continuous space we describe the infinite volume ground state configurations (GSCs) of pair interactions \vfi and \vfi+\psi, where \vfi is the inverse Fourier transform of a nonnegative function vanishing outside the sphere of radius $K_0$, and $\psi$ is any nonnegative finite-range interaction of range $r_0\leq\gamma_d/K_0$, where $\gamma_3=\sqrt{6}\pi$. In three dimensions the decay of \vfi can be as slow as $\sim r^{-2}$, and an interaction of asymptotic form $\sim\cos(K_0r+\pi/2)/r^3$ is among the examples. At a dimension-dependent density $\rho_d$ the ground state of \vfi is a unique Bravais lattice, and for higher densities it is continuously degenerate: any union of Bravais lattices whose reciprocal lattice vectors are not shorter than $K_0$ is a GSC. Adding $\psi$ decreases the ground state degeneracy which, nonetheless, remains continuous in the open interval $(\rho_d,\rho_d')$, where $\rho_d'$ is the close-packing density of hard balls of diameter $r_0$. The ground state is unique at both ends of the interval. In three dimensions this unique GSC is the bcc lattice at $\rho_3$ and the fcc lattice at $\rho_3'=\sqrt{2}/r_0^3$.Comment: Published versio

Restoration of a wild grey partridge shoot: a major development in the Sussex study, UK

Restauración de la caza de la perdiz pardilla: un importante progreso en el estudio de Sussex, Reino Unido Desde hace una generación se conoce la base científica de la gestión de la perdiz pardilla. Ésta incluye el control de los depredadores de nidos, la provisión de material para la nidificación, tener suficientes insectos para alimentar a las crías, y un control adecuado de la caza. Más recientemente también se ha considerado importante proveer alimento para las aves adultas y y hábitats para protegerlas de las aves rapaces. El abastecimiento del hábitat puede ser caro, pero en el Reino Unido los costos pueden recuperarse parcialmente mediante proyectos agro-medioambientales. El propietario de la tierra aún tiene que pagar por los servicios de los guardabosques. Desde 2003/2004, una parte del área de estudio de Sussex de la GWCT ha puesto en práctica estos principios de gestión ambiental, con la intención de restaurar la caza de la perdiz pardilla en esta zona del sur de Inglaterra. Los resultados han sido impresionantes, con un aumento de la densidad de parejas en primavera de 0,3/100 ha en 2003 hasta casi 20 parejas/100 ha en el 2010, en un área total de más de 10 km2. Durante los últimos dos años se ha practicado la caza de la perdiz pardilla y los propietarios de las tierras y sus equipos se han ganado el reconocimiento nacional por su labor conservacionista.Restauración de la caza de la perdiz pardilla: un importante progreso en el estudio de Sussex, Reino Unido Desde hace una generación se conoce la base científica de la gestión de la perdiz pardilla. Ésta incluye el control de los depredadores de nidos, la provisión de material para la nidificación, tener suficientes insectos para alimentar a las crías, y un control adecuado de la caza. Más recientemente también se ha considerado importante proveer alimento para las aves adultas y y hábitats para protegerlas de las aves rapaces. El abastecimiento del hábitat puede ser caro, pero en el Reino Unido los costos pueden recuperarse parcialmente mediante proyectos agro-medioambientales. El propietario de la tierra aún tiene que pagar por los servicios de los guardabosques. Desde 2003/2004, una parte del área de estudio de Sussex de la GWCT ha puesto en práctica estos principios de gestión ambiental, con la intención de restaurar la caza de la perdiz pardilla en esta zona del sur de Inglaterra. Los resultados han sido impresionantes, con un aumento de la densidad de parejas en primavera de 0,3/100 ha en 2003 hasta casi 20 parejas/100 ha en el 2010, en un área total de más de 10 km2. Durante los últimos dos años se ha practicado la caza de la perdiz pardilla y los propietarios de las tierras y sus equipos se han ganado el reconocimiento nacional por su labor conservacionista.The scientific basis of wild grey partridge management has been known for a generation. This includes controlling nest predators, providing nesting cover, having sufficient insect food for chicks and appropriate rates of shooting. More recently, measures such as providing food for adult birds and habitats for protection from birds of prey have also been considered important. Habitat provision can be expensive, but in the UK costs can be partially recovered through governmental agri–environment schemes. The landowner still needs to pay for the essential gamekeeper. Since 2003/04, one part of the Game & Wildlife Conservation Trust’s (GWCT) Sussex Study area has put these principles of environmental management into practice with the aim of restoring a wild grey partridge shoot to this part of Southern England. Results have been impressive, with the spring pair density increasing from 0.3 pairs/100 ha in 2003 to nearly 20 pairs/100 ha in 2010 on an area of just over 10 km2. Over the past two years a wild grey partridge shoot has taken place, and the landowner and his team have gained national recognition for their conservation work

Inventory of Non-Energy Sources of Greenhouse Gas Emissions in Hawaii Phase I

International concern for global climate change has stimulated a wide range of data gathering and analysis efforts worldwide. The recognition that certain atmospheric gases, many of which are anthropogenic in origin, have the capacity to absorb infrared radiation-and thus trap heat in the atmosphere--has focused research efforts on these so-called "greenhouse" gases. In order for a country to assess its contribution to such global warming, it must first develop an emissions inventory of greenhouse gas sources and sinks. In the United States, the U.S. Environmental Protection Agency (EPA) has recently published such an inventory (U.S. EPA, 1994) and has been funding the efforts of each state to develop their own inventories of sources of greenhouse gas emissions (U.S. EPA, 1995, hereafter titled the State Phase I Workbook). It is this latter document which serves as the basis for the present report by providing the bulk of its overall methodology.Clean Air Branch, Department of Health, State of Hawai

Plantar Pressure Distribution Patterns During Gait in Diabetic Neuropathy Patients with a History of Foot Ulcers

OBJECTIVE: To investigate and compare the influence of a previous history of foot ulcers on plantar pressure variables during gait of patients with diabetic neuropathy. INTRODUCTION: Foot ulcers may be an indicator of worsening diabetic neuropathy. However, the behavior of plantar pressure patterns over time and during the progression of neuropathy, especially in patients who have a clinical history of foot ulcers, is still unclear. METHODS: Subjects were divided into the following groups: control group, 20 subjects; diabetic neuropathy patients without foot ulcers, 17 subjects; and diabetic neuropathy patients with at least one healed foot ulcer within the last year, 10 subjects. Plantar pressure distribution was recorded during barefoot gait using the Pedar-X system. RESULTS: Neuropathic subjects from both the diabetic neuropathy and DNU groups showed higher plantar pressure than control subjects. At midfoot, the peak pressure was significantly different among all groups: control group (139.4±76.4 kPa), diabetic neuropathy (205.3±118.6 kPa) and DNU (290.7±151.5 kPa) (p=0.008). The pressure-time integral was significantly higher in the ulcerated neuropathic groups at midfoot (CG: 37.3±11.4 kPa.s; DN: 43.3±9.1 kPa.s; DNU: 68.7±36.5 kPa.s; p=0.002) and rearfoot (CG: 83.3±21.2 kPa.s; DN: 94.9±29.4 kPa.s; DNU: 102.5±37.9 kPa.s; p=0.048). CONCLUSION: A history of foot ulcers in the clinical history of diabetic neuropathy subjects influenced plantar pressure distribution, resulting in an increased load under the midfoot and rearfoot and an increase in the variability of plantar pressure during barefoot gait. The progression of diabetic neuropathy was not found to influence plantar pressure distribution

The Circuit Ideal of a Vector Configuration

The circuit ideal, \ica, of a configuration \A = \{\a_1, ..., \a_n\} \subset \Z^d is the ideal generated by the binomials {\x}^{\cc^+} - {\x}^{\cc^-} \in \k[x_1, ..., x_n] as \cc = \cc^+ - \cc^- \in \Z^n varies over the circuits of \A. This ideal is contained in the toric ideal, \ia, of \A which has numerous applications and is nontrivial to compute. Since circuits can be computed using linear algebra and the two ideals often coincide, it is worthwhile to understand when equality occurs. In this paper we study \ica in relation to \ia from various algebraic and combinatorial perspectives. We prove that the obstruction to equality of the ideals is the existence of certain polytopes. This result is based on a complete characterization of the standard pairs/associated primes of a monomial initial ideal of \ica and their differences from those for the corresponding toric initial ideal. Eisenbud and Sturmfels proved that \ia is the unique minimal prime of \ica and that the embedded primes of \ica are indexed by certain faces of the cone spanned by \A. We provide a necessary condition for a particular face to index an embedded prime and a partial converse. Finally, we compare various polyhedral fans associated to \ia and \ica. The Gr\"obner fan of \ica is shown to refine that of \ia when the codimension of the ideals is at most two.Comment: 25 page