Electrons on a spherical surface: Physical properties and hollow spherical clusters

We discuss thephysical properties of a non interacting electron gas constrained to a spherical surface. In particular we consider its chemical potentials, its ionization potential,and its electric static polarizability. All these properties are discussed analytically as functions of the number N of electrons. The trends obtained with increasing N are compared with those of the corresponding properties experimentally measured or theoretically evaluated for quasi spherical hollow atomic and molecular clusters. Most of the properties investigated display similar trends, characterized by a prominence of shell effects. This leads to the de\ufb01nition of a scale-invariant distribution of magic numbers which follows a power law with critical exponent 120.5. We conclude that our completely mechanistic and analytically tractable model can be useful for the analysis of self-assembling complex systems

Capsule impaction presenting as acute small bowel perforation: a case series

INTRODUCTION: Perforation caused by capsule endoscopy impaction is extremely rare and, at present, only five cases of perforation from capsule endoscopy impaction are reported in the literature. CASE PRESENTATION: We report here two cases of patients with undiagnosed small bowel stenosis presenting with acute perforation after capsule endoscopy. Strictures in the small bowel were likely the inciting mechanism leading to acute small bowel obstruction and subsequent distension and perforation above the capsule in the area of maximal serosal tension. Case 1 was a 55-year-old Italian woman who underwent capsule endoscopy because of recurrent postprandial cramping pain and iron deficiency anemia, in the setting of negative imaging studies including an abdominal ultrasound, upper endoscopy, colonoscopy and small bowel follow-through radiograph. She developed a symptomatic bowel obstruction approximately 36 hours after ingestion of the capsule. Emergent surgery was performed to remove the capsule, which was impacted at a stenosis due to a previously undiagnosed ileal adenocarcinoma, leading to perforation. Case 2 was a 60-year-old Italian man with recurrent episodes of abdominal pain and diarrhea who underwent capsule endoscopy after conventional modalities, including comprehensive blood and stool studies, computed tomography, an abdominal ultrasound, upper endoscopy, colonoscopy, barium enema and small bowel follow-through, were not diagnostic. Our patient developed abdominal distension, acute periumbilical pain, fever and leukocytosis 20 hours after capsule ingestion. Emergent surgery was performed to remove the capsule, which was impacted at a previously undiagnosed ileal Crohn’s stricture, leading to perforation. CONCLUSIONS: The present report shows that, although the risk of acute complication is very low, the patient should be informed of the risks involved in capsule endoscopy, including the need for emergency surgical exploration

Dynamical decoherence in a cavity with a large number of two-level atoms

We consider a large number of two-level atoms interacting with the mode of a cavity in the rotating-wave approximation (Tavis-Cummings model). We apply the Holstein-Primakoff transformation to study the model in the limit of the number of two-level atoms, all in their ground state, becoming very large. The unitary evolution that we obtain in this approximation is applied to a macroscopic superposition state showing that, when the coherent states forming the superposition are enough distant, then the state collapses on a single coherent state describing a classical radiation mode. This appear as a true dynamical effect that could be observed in experiments with cavities.Comment: 9 pages, no figures. This submission substitutes paper quant-ph/0212148 that was withdrawn. Version accepted for publication in Journal of Physics B: Atomic, Molecular & Optical Physic

Nonlocal field correlations and dynamical Casimir-Polder forces between one excited- and two ground-state atoms

The problem of nonlocality in the dynamical three-body Casimir-Polder interaction between an initially excited and two ground-state atoms is considered. It is shown that the nonlocal spatial correlations of the field emitted by the excited atom during the initial part of its spontaneous decay may become manifest in the three-body interaction. The observability of this new phenomenon is discussed.Comment: 17 pages, 1 figure, sub. to Phys. Rev.

Casimir-Polder potentials as entanglement probe

We have considered the interaction of a pair of spatially separated two-level atoms with the electromagnetic field in its vacuum state and we have analyzed the amount of entanglement induced between the two atoms by the non local field fluctuations. This has allowed us to characterize the quantum nature of the non local correlations of the electromagnetic field vacuum state as well as to link the induced quantum entanglement with Casimir-Polder potentials.Comment: Published on Europhysics Letters 78 (2007) 3000

A review, timeline, and categorization of learning design tools

Enabling teachers to define or portray efficient teaching ideas for sharing, reuse or adaptation has attracted the interest of Learning Design researchers and has led to the development of a variety of learning design tools. In this paper, we introduce a multi-dimensional framework for the analysis of learning design tools and use it to review twenty-nine tools currently available to researchers and practitioners. Lastly, we categorise these tools according to the main functionality that they offer

Efficacy of lamivudine to prevent hepatitis reactivation in hepatitis B virus-infected patients treated for non-Hodgkin lymphoma.

The association of hepatitis viruses with non-Hodgkin lymphomas (NHL) is not rare. Several authors have reported an exceeding prevalence of hepatitis C virus (HCV)1-3 or of hepatitis B virus (HBV)4,5 infection in patients affected by NHL. A sustained increase of alanine aminotransferase (ALT) associated with high levels of HBV viremia (HBV-DNA) 1 to 2 months after the suspension of chemotherapy has been described in patients suffering from NHL and infected by HBV.7,8 Recently, a nucleotide analogue (lamivudine) was shown to be beneficial in HBV-infected patients with signs of active replication.6 The aim of this study was to investigate the role of lamivudine to treat or to prevent hepatitis reactivation in HBV-infected subjects suffering from NHL and undergoing chemotherapy

Vortex Fluctuations in High-Tc Films: Flux Noise Spectrum and Complex Impedance

The flux noise spectrum and complex impedance for a 500 {\AA} thick YBCO film are measured and compared with predictions for two dimensional vortex fluctuations. It is verified that the complex impedance and the flux noise spectra are proportional to each other, that the logarithm of the flux noise spectra for different temperatures has a common tangent with slope $\approx -1$, and that the amplitude of the noise decreases as $d^{-3}$, where $d$ is the height above the film at which the magnetic flux is measured. A crossover from normal to anomalous vortex diffusion is indicated by the measurements and is discussed in terms of a two-dimensional decoupling.Comment: 5 pages including 4 figures in two columns, to appear in Phys. Rev. Let