477 research outputs found
One-dimensional Rydberg Gas in a Magnetoelectric Trap
We study the quantum properties of Rydberg atoms in a magnetic
Ioffe-Pritchard trap which is superimposed by a homogeneous electric field.
Trapped Rydberg atoms can be created in long-lived electronic states exhibiting
a permanent electric dipole moment of several hundred Debye. The resulting
dipole-dipole interaction in conjunction with the radial confinement is
demonstrated to give rise to an effectively one-dimensional ultracold Rydberg
gas with a macroscopic interparticle distance. We derive analytical expressions
for the electric dipole moment and the critical linear density of Rydberg
atoms.Comment: 4 pages, 2 figure
The influence of a superconducting split-pair solenoid as an insertion device on the performance of a storage ring for synchrotron radiation
EINFLUSS EINES ALS INSERTION DEVICE VERWENDETEN SUPRALEITENDEN SPLIT-PAIR SOLENOIDEN AUF DAS VERHALTEN EINES SPEICHERRINGES FĂR SYNCHROTRONSTRAHLUNG
Zur Erhöhung der Photonenenergie von Synchrotronstrahlungsquellen wird die Verwendung von starken nichtlinearen Magneten in Betracht gezogen. Solche Magnete können einen starken EinfluĂ auf die Funktion von Speicherringen ausĂŒben, da sie die Emittanz vergröĂern und die dynamische Apertur verringern können. In der vorliegenden Arbeit wird eine Methode vorgestellt, mit deren Hilfe der EinfluĂ der nichtlinearen Felder auf die dynamische Apertur berechnet werden kann. Mit dieser Methode wird die mögliche Auswirkung eines als WellenlĂ€ngenschieber eingesetzten kommerziellen 12 T Split-pair Solenoiden auf die dynamische Apertur der zukĂŒnftigen Synchrotronstrahlungsquelle ANKA untersucht
Interaction-induced stabilization of circular Rydberg atoms
We discuss a candidate solution for the controlled trapping and manipulation
of two individual Rydberg atoms by means of a magnetic Ioffe-Pritchard trap
that is superimposed by a constant electric field. In such a trap Rydberg atoms
experience a permanent electric dipole moment that can be of the order of
several hundred Debye. The interplay of electric dipolar repulsion and three
dimensional magnetic confinement leads to a well controllable equilibrium
configuration with tunable trap frequency and atomic distance. We thoroughly
investigate the trapping potentials and analyze the interaction-induced
stabilization of two such trapped Rydberg atoms. Possible limitations and
collapse scenarios are discussed.Comment: 18 pages, 5 figure
Hundred photon microwave ionization of Rydberg atoms in a static electric field
We present analytical and numerical results for the microwave excitation of
nonhydrogenic atoms in a static electric field when up to 1000 photons are
required to ionize an atom. For small microwave fields, dynamical localization
in photon number leads to exponentially small ionization while above quantum
delocalization border ionization goes in a diffusive way. For alkali atoms in a
static field the ionization border is much lower than in hydrogen due to
internal chaos.Comment: revtex, 4 pages, 5 figure
Classical Evolution of Quantum Elliptic States
The hydrogen atom in weak external fields is a very accurate model for the
multiphoton excitation of ultrastable high angular momentum Rydberg states, a
process which classical mechanics describes with astonishing precision. In this
paper we show that the simplest treatment of the intramanifold dynamics of a
hydrogenic electron in external fields is based on the elliptic states of the
hydrogen atom, i.e., the coherent states of SO(4), which is the dynamical
symmetry group of the Kepler problem. Moreover, we also show that classical
perturbation theory yields the {\it exact} evolution in time of these quantum
states, and so we explain the surprising match between purely classical
perturbative calculations and experiments. Finally, as a first application, we
propose a fast method for the excitation of circular states; these are
ultrastable hydrogenic eigenstates which have maximum total angular momentum
and also maximum projection of the angular momentum along a fixed direction. %Comment: 8 Pages, 2 Figures. Accepted for publication in Phys. Rev.
Generation of x-ray radiation in a storage ring by a superconductive cold-bore in-vacuum undulator
Long-lived magnetism on chondrite parent bodies
publisher: Elsevier articletitle: Long-lived magnetism on chondrite parent bodies journaltitle: Earth and Planetary Science Letters articlelink: http://dx.doi.org/10.1016/j.epsl.2017.07.035 content_type: article copyright: © 2017 The Authors. Published by Elsevier B.V.© 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). The attached file is the published version of the article
Gendered endings: Narratives of male and female suicides in the South African Lowveld
This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11013-012-9258-y. Copyright @ Springer Science+Business Media, LLC 2012.Durkheimâs classical theory of suicide rates being a negative index of social solidarity downplays the salience of gendered concerns in suicide. But gendered inequalities have had a negative impact: worldwide significantly more men than women perpetrate fatal suicides. Drawing on narratives of 52 fatal suicides in Bushbuckridge, South Africa, this article suggests that Bourdieuâs concepts of âsymbolic violenceâ and âmasculine dominationâ provide a more appropriate framework for understanding this paradox. I show that the thwarting of investments in dominant masculine positions have been the major precursor to suicides by men. Men tended to take their own lives as a means of escape. By contrast, women perpetrated suicide to protest against the miserable consequences of being dominated by men. However, contra the assumption of Bourdieuâs concept of âhabitusâ, the narrators of suicide stories did reflect critically upon gender constructs
Exploiting inflammation for therapeutic gain in pancreatic cancer
Pancreatic ductal adenocarcinoma (PDAC) is an aggressive malignancy associated with <5% 5-year survival, in which standard chemotherapeutics have limited benefit. The disease is associated with significant intra- and peritumoral inflammation and failure of protective immunosurveillance. Indeed, inflammatory signals are implicated in both tumour initiation and tumour progression. The major pathways regulating PDAC-associated inflammation are now being explored. Activation of leukocytes, and upregulation of cytokine and chemokine signalling pathways, both have been shown to modulate PDAC progression. Therefore, targeting inflammatory pathways may be of benefit as part of a multi-target approach to PDAC therapy. This review explores the pathways known to modulate inflammation at different stages of tumour development, drawing conclusions on their potential as therapeutic targets in PDAC
TEAD and YAP regulate the enhancer network of human embryonic pancreatic progenitors.
The genomic regulatory programmes that underlie human organogenesis are poorly understood. Pancreas development, in particular, has pivotal implications for pancreatic regeneration, cancer and diabetes. We have now characterized the regulatory landscape of embryonic multipotent progenitor cells that give rise to all pancreatic epithelial lineages. Using human embryonic pancreas and embryonic-stem-cell-derived progenitors we identify stage-specific transcripts and associated enhancers, many of which are co-occupied by transcription factors that are essential for pancreas development. We further show that TEAD1, a Hippo signalling effector, is an integral component of the transcription factor combinatorial code of pancreatic progenitor enhancers. TEAD and its coactivator YAP activate key pancreatic signalling mediators and transcription factors, and regulate the expansion of pancreatic progenitors. This work therefore uncovers a central role for TEAD and YAP as signal-responsive regulators of multipotent pancreatic progenitors, and provides a resource for the study of embryonic development of the human pancreas
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